Unit 1 Biology (1st Year CSE)

                     

Course Syllabus and Suggestive Readings

Unit 1   Importance of Biology In Engineering

Introduction: Fundamental Differences between Science and engineering by drawing a comparison between eye and camera, Bird flying and aircraft. Significance of Biology in Engineering, Discuss how biological observations of 18th Century that lead to major discoveries, Examples from Brownian motion and the origin of thermodynamics by referring to the original observation of Robert and Julius Mayor.

Genetics: Mendel’s laws, Concept of segregation and independent assortment, concept of allele, gene mapping, Gene interaction, Epitasis, Meiosis and Mitosis as a part of genetics. Mechanism of how genetic material passes from parent to offspring. Concepts of recessiveness and dominance. Concept of mapping of phenotype to Genes, single gene disorders in humans, concept of complementation using human genetics.

Unit 2 Biosensors and measurement system

Medical Instrumentation: Sources of biomedical Signals, Basic medical Instrumentation system, Performance requirements of medical Instrumentation System, Microprocessors in Medical instruments, PC base medical Instruments, General constraints in design of medical Instrumentation system, Regulation of Medical Devices.

Measurement System: Specification of instruments, Statics & Dynamic characteristics of medical instruments, Classification of errors. Statistical analysis, Reliability, Accuracy, Fidelity, Speed of responses, Linearization of technique,Data acquisition System.

Biological sensors: Sensors/ receptors in the human body, basic organization of nervoussystem- neural mechanism, Chemoreceptor: hot and cold receptors, sensors for smell, sound, vision, Ion exchange membrane electrodes, enzyme, glucose sensors, immunosensors & biosensors & applications of biosensors.

Unit 3  Bio Medical Instrumentation

Electrical stimulus and biophysical activity: Patient, electrical shock and hazards, leakage current, Electrical activity of heart (ECG), Electrical activity of brain (EEG), Electrorentinogram (ERG), Electro-occologram (EOG), Electromyogram(EMG).

Biomedical recording systems:  Basic Recording system , General consideration for signal conditioners Preamplifiers, Differential Amplifier , Isolation Amplifier, Vectorcardiograph, Phonocardiograph,  Other biomedical records, , , Patient isolation and accident prevention.

Tissue Engineering:

Recombinant DNA technology, Stem cell biology & Tissue Engineering


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CHAPTER 1

Lecture 1.1.1

co1-Identify the biological concepts from an engineering perspective.

•This subject is designed to impart fundamental knowledge on basic of genetics and emerging fields of biology like biomedical recording system and medical instrumentation.

•It is designed to impart knowledge that how to apply basics of biology in engineering.

Science and Engineering

•Generally, Science is the study of the physical world, while Engineering applies scientific knowledge to design processes, structures or equipment.

• Both Engineers and Scientists will have a strong knowledge of science, mathematics and technology, but Engineering students will learn to apply these principles to designing creative solutions to Engineering challenges. So when we think of a scientist versus engineer, the two aren’t separate entities but belong to each other – without science, there wouldn’t be engineering.

•The terms science and technology, are often pronounced in the same breath and used as synonyms, because they are closely intertwined, that their difference is often times ignored.

• Science is all about acquiring knowledge of the natural phenomenon along with the reasons for such phenomenon, like Why are leaves green? How do plants make their food? And so forth. When this knowledge is put to practice, to solve human needs or problems, it is termed as technology.

•So, in short, science deals with theories, principles and laws whereas technology is all about products, processes and designs.

•Biology is the natural science that studies life and living organisms, including their physical structure, chemical processes, molecular interactions, physiological mechanisms, development and evolution.

•There are three major branches of biology – botany, zoology and microbiology. 

•BOTANY study of plants

•ZOOLOGY study of animals

•MICROBIOLOGY study of microbes

•Biomimicry, as it’s called, is a method for creating solutions to human challenges by emulating designs and ideas found in nature. It’s used everywhere: buildings, vehicles, and even materials.

•There are three main ways biomimicry can work.

• First, a design can mimic form or shape, like paint that helps surfaces self-clean the same way as a lotus leaf. Second, there is mimicking process, like patterning autonomous vehicle networks on how ants and bees communicate as a hive.

Difference Between Eye And Camera

Eye vs Camera

Eye is an organ of sight while a camera is equipment that is used to record images.

The first and the foremost difference between an eye and a camera is that an eye cannot record an image. The eyes use living cells to detect and interpret the light and convert these into electrical signals that are relayed to the brain and processed into an image. The camera on the other hand uses a diaphragm from where the image is recorded on film or like in modern cameras on tape or digitally.

A camera sees in 2 dimensions while the eye sees in 3 dimensions. This means that when we see with our eyes we see height, width and depth. With a camera we only see height and width. There is no way to have the depth in the picture as a photograph is a flat medium. This is mainly achieved by the stereoscopic vision of the eye. A simple demonstration of this can be trying to bring the forefingers of both hands to meet from the sides. This is much simpler to do with both eyes open than with only one eye or almost impossible with a camera.

While changing the focus the retina and parts of the pupil adjust the size accordingly. However, in a camera the focus is changed by the movement of the lens. Eye has a blind spot which is also known as scotoma, whereas, the cameras do not have any such limitations. The eye can also adapt itself to the dark and within a few seconds one can get start seeing better in the dark. However, if a camera is not equipped to capture images in the dark it can never get accustomed.

The eye is highly sensitive to the dust and foreign particles settling on the outer film. In a camera there is no such problem as any dust can simply be wiped off the lens.

Summary

  1. Eye is a live organ for sight whereas a camera is an equipment to capture images.
  2. Eye uses live cells to detect light while the camera uses a diaphragm to detect light and capture images.
  3. Stereoscopic vision of eyes allows 3 dimensional images while camera captures only 2 dimensional images.
  4. The pupil adjusts the size while focusing while in a camera lens moves to change focus.
  5. Eyes have blind spots while cameras do not.

Lecture Topic 1.1.2

CO2-Development of artificial systems mimicking human action.

Introduction

Biomimicry is a type of innovation where scientists and engineers look for solutions to the challenges that face human beings by using the patterns of nature. Nature has configurations that are time tested and accurate. Human beings aim to create processes that will be sustainable for the future generations and the later life on earth. There are many instances where biomimicry has solved problems in the natural world.

In engineering, biomimicry applies because nature inspires designs like navigation vessels, ships among other creative and innovative products (4). Nature acts an inspiration for many designs and innovations. One of the main innovations is how airplanes have taken the shape of birds.

Discussion

For over a thousand years, man has wanted to fly and to move from one point to another. Flying is the fastest mode of transportation, and people can move from city to city to carry out business and to look for new frontiers. Before man invented airplanes, he would rely on ships that would spend many days on the voyage.

Airplanes eradicated the problem of accessibility and made it faster and more convenient to do business. Birds fly so effortlessly because of the adaptations that they have. Birds have streamlined shapes so that when they are in flight the air can flow on their surface smoothly. Engineers used the shape of the birds as inspiration to model the planes (4). Most airplanes have a streamlined shape so that they do not face air resistance when they are in motion.

Secondly, birds have smooth and sometimes glossy surface. Birds groom their feathers with their beaks to makes sure that their body is smooth as they fly (2). Airplanes also have polished surfaces, and this prevents air resistance. Thirdly, birds use a concept where they fly in a V shape when they are in a flock. This mode of flying has enabled birds to travel greater distances. The V formation aids in collaboration, because as each bird flies, it adds more energy to the group, and they can keep up many miles in flight.

The birds keep changing positions and rotate their place in the stack, and this helps them go for long distances without tiring. There are some researchers from Stanford University who utilized this trait and concluded that if jets use the same trait, they can save on fuel. They purported that if jets fly in a V-shape and alternate their positions, they would manage to save their fuel up to 15%.

The concept of biomimicry has inspired the airplane wings. When birds want to take off, they raise their wings thereby creating a low pressure, and the body goes up through the process of ‘lift’. Airplanes use the same notion while taking off and landing. The scientists mimic the movements of the birds while modeling the wings. Airplane wings have taken the same shape as the birds’ wing and the taper outside. The two wings have different thicknesses as they move from the body.

There are some developments expected in future. Shaker Meguid, a medical engineer, said in 2008 that he aims to make changes to aerodynamics (1). He said that when birds are in the air, they extend their wings so far, and this helps them to stay high and to reduce the air drag. He also says that when birds what to move faster, they close their wings and planes can use the same concept that he calls ‘wing morphing’.

Human beings are always aiming to make new discoveries and alteration to their designs. Most modern planes have fixed wings that cannot change in angles. However, these planes have flaps on the wings that move up and down depending on where the plane is. Today, the only developments on a plane wing are the flaps and ailerons. There have been developments to make a wing that morphs. Scientists say that when a wing transforms, it will be easy to steer when it is in the air, and it will make flying easier. This revolutionizing of the airplane by biomimicry is something that in the works.

•Bio-inspired technologies: Biologically-inspired design (or BID) has become an important and increasingly wide-spread movement in design for environmentally-conscious sustainable development.

•Aircraft wing design and flight techniques are being inspired by birds and bats.

•Biorobot :-A biological organism that has been created and designed by artificial means. A person who performs robot-like tasks, or performs tasks in place of a robot.

•Suction nozzle of vacuum cleaner: inspired by proboscis of flies

•Spider web silk is as strong as the Kevlar used in bulletproof vests. Engineers could in principle use such a material, if it could be reengineered to have a long enough life, for parachute lines, suspension bridge cables, artificial ligaments for medicine, and other purposes. Spider silk is highly flexible, extremely stretchable, surpasses steel in strength, and most importantly, can be formed into a mesh that would stop a bullet.

Lecture Topic 1.1.3

CO2Development of artificial systems mimicking human action. 

Eye vs Camera

Eye is an organ of sight while a camera is equipment that is used to record images.

The first and the foremost difference between an eye and a camera is that an eye cannot record an image. The eyes use living cells to detect and interpret the light and convert these into electrical signals that are relayed to the brain and processed into an image. The camera on the other hand uses a diaphragm from where the image is recorded on film or like in modern cameras on tape or digitally.

A camera sees in 2 dimensions while the eye sees in 3 dimensions. This means that when we see with our eyes we see height, width and depth. With a camera we only see height and width. There is no way to have the depth in the picture as a photograph is a flat medium. This is mainly achieved by the stereoscopic vision of the eye. A simple demonstration of this can be trying to bring the forefingers of both hands to meet from the sides. This is much simpler to do with both eyes open than with only one eye or almost impossible with a camera.

While changing the focus the retina and parts of the pupil adjust the size accordingly. However, in a camera the focus is changed by the movement of the lens. Eye has a blind spot which is also known as scotoma, whereas, the cameras do not have any such limitations. The eye can also adapt itself to the dark and within a few seconds one can get start seeing better in the dark. However, if a camera is not equipped to capture images in the dark it can never get accustomed.

The eye is highly sensitive to the dust and foreign particles settling on the outer film. In a camera there is no such problem as any dust can simply be wiped off the lens.

Summary

  1. Eye is a live organ for sight whereas a camera is an equipment to capture images.
  2. Eye uses live cells to detect light while the camera uses a diaphragm to detect light and capture images.
  3. Stereoscopic vision of eyes allows 3 dimensional images while camera captures only 2 dimensional images.
  4. The pupil adjusts the size while focusing while in a camera lens moves to change focus.
  5. Eyes have blind spots while cameras do not

Our eyes are able to look around and adjust dynamically depending on the environment. Hence, most of us would assume that there is little-t0-no difference between the human eye and camera. However, things are a lot more complicated than it seems. We need to understand that there are two primary differences in the way they work. We can summarize these differences as follows

Difference in focusing on an image

Difference in processing colour

Human Eye vs Camera

Following are some of the major differences between a physical camera and the human eye.

Human EyesCameraFocusing on an ImageThe human eye contains small muscles that contract and relax – and this enables the eyes to change shape and stay focused on a moving object. These muscles also capable of changing the thickness of the lens to accommodate the image that is being viewedA camera cannot do this, hence, it relies on a variety of lens. This is the reason why photographers often change the lens of their camera according to the distance from the object. Moreover, cameras use mechanical parts to stay focused on a moving object.Processing ColourHuman eyes contain special types of cells called photoreceptors. There are two types – rods and cones. Rods are primarily used for low-light vision while cones are used for colour vision. There are 3 types of cones that respond to 3 different wavelengths of light. For instance, blue cones respond to short wavelengths while red cones respond to long wavelengths and green cones respond to medium wavelengths. The colour we see is the result of the brain activating the cones in various combinations.Cameras use something called photosites to collect light. A typical camera has millions of these light collectors that hold the light and then convert it into a signal that can be interpreted by electronic devices. Moreover, cameras use filters that break up light into its primary colours – red, blue and green. It reproduces the full spectrum image by combining these colours.Blind SpotsThe human eye has a blind spot – this is located at the point where the optic nerve joins the retina. Under normal circumstances, we do not notice this blindspot as the brain uses information from the other eye to complete the missing portion of the image.A camera does not have such a blind spot.

Lecture Topic 1.1.4

CO1Identify the biological concepts from an engineering perspective.CO2Development of artificial systems mimicking human action. 

•Bio-inspired technologies: Biologically-inspired design (or BID) has become an important and increasingly wide-spread movement in design for environmentally-conscious sustainable development.

•Aircraft wing design and flight techniques are being inspired by birds and bats.

•Biorobot :-A biological organism that has been created and designed by artificial means. A person who performs robot-like tasks, or performs tasks in place of a robot.

•Ant-Inspired Pheromone Sensors for Traffic Control.  Ant-based systems have special properties such as scalability, adaptability, and dynamicity, which are the main requirements for solving vehicle traffic congestion problem. Thus, ant-based algorithms are now being adopted by vehicle traffic systems (VTSs) to guide vehicles to less congested paths.

•Construction and architecture: Researchers studied the termite’s ability to maintain virtually constant temperature and humidity in their termite mounds.

•Suction nozzle of vacuum cleaner: inspired by proboscis of flies

•Spider web silk is as strong as the Kevlar used in bulletproof vests. Engineers could in principle use such a material, if it could be reengineered to have a long enough life, for parachute lines, suspension bridge cables, artificial ligaments for medicine, and other purposes. Spider silk is highly flexible, extremely stretchable, surpasses steel in strength, and most importantly, can be formed into a mesh that would stop a bullet.

Lecture topic 1.1.5

CO2-Development of artificial systems mimicking human action.

BIOLOGICAL OBSERVATIONS OF 18TH CENTURY THAT LEAD TO MAJOR DISCOVERIES

•In the early 18th century, botanist Carl Linnaeus established the classification system that we use today in his work, Systema naturae (System of nature). This system of binomial nomenclature assigns a two-part name to species in which the genus name is capitalized and precedes the species epithet; both are italicized. For example, the scientific name for human beings is Homo sapiens. Linnaean classification follows the taxonomic categories: Kingdom, Phylum, Class, Order, Family, Genus, Species. We now have added Domain as the largest category, before Kingdom. Classification of organisms can be a sticky and subjective process, and the framework was set primarily by Linnaeus and his contemporaries.

•Now we fast forward to 1827 where Robert Brown, a British botanist, is observing a suspended pollen grain in water. While looking at this pollen grain underneath a microscope, he notices that it undergoes a type of random walk. The figure below depicts the type of random, seemingly unpredictable motion, that the suspended particle underwent. This random motion is now referred to as BROWNIAN MOTION, but the motion itself may be easily remembered as the “Drunken Sailor Walk”. At first Brown attributed this motion to signs of life

Brownian motion is the random motion of a particle as a result of collisions with surrounding gaseous molecules. Diffusiophoresis is the movement of a group of particles induced by a concentration gradient. This movement always flows from areas of high concentration to areas of low concentration.

First Law of Thermodynamics

Before we get into the first law of thermodynamics we need to understand the relation between heat and work and the concept of internal energy. Just like mass, energy is always conserved i.e. it can neither be created nor destroyed but it can be transformed from one form to another. Internal energy is a thermodynamic property of the system that refers to the energy associated with the molecules of the system which includes kinetic energy and potential energy.

Whenever a system goes through any change due to interaction of heat, work and internal energy, it is followed by numerous energy transfer and conversions. However, during these transfers, there is no net change in the total energy.

Similarly, if we look at the first law of thermodynamics it affirms that heat is a form of energy. What it means is that the thermodynamic processes are governed by the principle of conservation of energy. The first law of thermodynamics is also sometimes referred to as the Law of Conservation of Energy.

A thermodynamic system in an equilibrium state possesses a state variable known as the internal energy(E). Between two systems the change in the internal energy is equal to the difference of the heat transfer into the system and the work done by the system.

The first law of thermodynamics states that the energy of the universe remains the same. Though it may be exchanged between the system and the surroundings, it can’t be created or destroyed. The law basically relates to the changes in energy states due to work and heat transfer. It redefines the conservation of energy concept.

First Law of ThermodynamicsThe First Law of Thermodynamics states that heat is a form of energy, and thermodynamic processes are therefore subject to the principle of conservation of energy. This means that heat energy cannot be created or destroyed. It can, however, be transferred from one location to another and converted to and from other forms of energy.

To help you understand the meaning of the First Law, we can take the common example of a heat engine. In a Heat engine, the thermal energy is converted into mechanical energy and the process also is vice versa. Heat engines are mostly categorized as an open system. The basic working principle of a heat engine is that it makes use of the different relationships between heat, pressure and volume of a working fluid which is usually a gas. Sometimes phase changes might also occur involving a gas to liquid and back to gas.

CHAPTER 2

Lecture Topic 1.2.1

CO3-Explain the basic of genetics that helps to identify and formulate problems

Mendel’s Laws of Inheritance

Inheritance can be defined as the process of how a child receives genetic information from the parent. The whole process of heredity is dependent upon inheritance and it is the reason that the offsprings are similar to the parents. This simply means that due to inheritance, the members of the same family possess similar characteristics.

It was only during the mid 19th century that people started to understand inheritance in a proper way. This understanding of inheritance was made possible by a scientist named Gregor Mendel, who formulated certain laws to understand inheritance known as Mendel’s laws of inheritance.

Between 1856-1863, Mendel conducted the hybridization experiments on the garden peas. During that period, he chose some distinct characteristics of the peas and conducted some cross-pollination/ artificial pollination on the pea lines that showed stable trait inheritance and underwent continuous self-pollination. Such pea lines are called true-breeding pea lines.

Also Refer: Mendel’s Laws of Inheritance: Mendel’s Contribution

Why was Pea Plant Selected for Mendel’s Experiments?

He selected a pea plant for his experiments for the following reasons:

  1. The pea plant can be easily grown and maintained.
  2. They are naturally self-pollinating but can also be cross-pollinated.
  3. It is an annual plant, therefore, many generations can be studied within a short period of time.
  4. It has several contrasting characters.

Mendel conducted 2 main experiments to determine the laws of inheritance. These experiments were:

  1. Monohybrid Cross
  2. Dihybrid Cross

While experimenting, Mendel found that certain factors were always being transferred down to the offspring in a stable way. Those factors are now called genes i.e. genes can be called the units of inheritance.

Mendel’s Experiments

Mendel experimented on a pea plant and considered 7 main contrasting traits in the plants. Then, he conducted both the experiments to determine the aforementioned inheritance laws. A brief explanation of the two experiments is given below.

Monohybrid Cross

In this experiment, Mendel took two pea plants of opposite traits (one short and one tall) and crossed them. He found the first generation offspring were tall and called it F1 progeny. Then he crossed F1 progeny and obtained both tall and short plants in the ratio 3:1. To know more about this experiment, visit Monohybrid Cross – Inheritance Of One Gene.

Mendel even conducted this experiment with other contrasting traits like green peas vs yellow peas, round vs wrinkled, etc. In all the cases, he found that the results were similar. From this, he formulated the laws of Segregation And Dominance.

Dihybrid Cross

In a dihybrid cross experiment, Mendel considered two traits, each having two alleles. He crossed wrinkled-green seed and round-yellow seeds and observed that all the first generation progeny (F1 progeny) were round-yellow. This meant that dominant traits were the round shape and yellow colour.

He then self-pollinated the F1 progeny and obtained 4 different traits: round-yellow, round-green, wrinkled-yellow, and wrinkled-green seeds in the ratio 9:3:3:1.

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After conducting research for other traits, the results were found to be similar. From this experiment, Mendel formulated his second law of inheritance i.e. law of Independent Assortment.

Conclusions from Mendel’s Experiments

  • The genetic makeup of the plant is known as the genotype. On the contrary, the physical appearance of the plant is known as phenotype.
  • The genes are transferred from parents to the offspring in pairs known as alleles.
  • During gametogenesis when the chromosomes are halved, there is a 50% chance of one of the two alleles to fuse with the allele of the gamete of the other parent.
  • When the alleles are the same, they are known as homozygous alleles and when the alleles are different they are known as heterozygous alleles.

Mendel’s laws

Law of Dominance

This is also called Mendel’s first law of inheritance. According to the law of dominance, hybrid offspring will only inherit the dominant trait in the phenotype. The alleles that are suppressed are called the recessive traits while the alleles that determine the trait are known as the dominant traits.

Law of Segregation

The law of segregation states that during the production of gametes, two copies of each hereditary factor segregate so that offspring acquire one factor from each parent. In other words, allele (alternative form of the gene) pairs segregate during the formation of gamete and re-unite randomly during fertilization. This is also known as Mendel’s third law of inheritance.

Law of Independent Assortment

Also known as Mendel’s second law of inheritance, the law of independent assortment states that a pair of traits segregates independently of another pair during gamete formation. As the individual heredity factors assort independently, different traits get equal opportunity to occur together.

Key Points on Mendel’s Laws

  • The law of inheritance was proposed by Gregor Mendel after conducting experiments on pea plants for seven years.
  • Mendel’s laws of inheritance include law of dominance, law of segregation and law of independent assortment.
  • The law of segregation states that every individual possesses two alleles and only one allele is passed on to the offspring.
  • The law of independent assortment states that the inheritance of one pair of genes is independent of inheritance of another pair.

The two experiments lead to the formulation of Mendel’s laws known as laws of inheritance which are:

  1. Law of Dominance
  2. Law of Segregation
  3. Law of Independent Assortment

Which is the universally accepted law of inheritance?

Law of segregation is the universally accepted law of inheritance. It is the only law without any exceptions. It states that each trait consists of two alleles which segregate during the formation of gametes and one allele from each parent combines during fertilization.

Why is the law of segregation known as the law of purity of gametes?

The law of segregation is known as the law of purity of gametes because a gamete carries only a recessive or a dominant allele but not both the alleles.

Why was the pea plant used in Mendel’s experiments?

Mendel picked pea plants in his experiments because the pea plant has different observable traits. It can be grown easily in large numbers and its reproduction can be manipulated. Also, pea has both male and female reproductive organs, so they can self-pollinate as well as cross-pollinate.

What was the main aim of Mendel’s experiments?

The main aim of Mendel’s experiments was:

  • To determine whether the traits would always be recessive.
  • Whether traits affect each other as they are inherited.
  • Whether traits could be transformed by DNA.

Lecture Topic 1.2.2

CO3-Explain the basic of genetics that helps to identify and formulate problems

Concept of Allele

An allele is one of two or more versions of DNA sequence (a single base or a segment of bases) at a given genomic location. An individual inherits two alleles, one from each parent, for any given genomic location where such variation exists. If the two alleles are the same, the individual is homozygous for that allele. If the alleles are different, the individual is heterozygous.

Biology Study Material
Biology Study Material

“Allele” is the word that we use to describe the alternative form or versions of a gene. People inherit one allele for each autosomal gene from each parent, and we tend to lump the alleles into categories. Typically, we call them either normal or wild-type alleles, or abnormal, or mutant alleles.

What Are Genes?

Genes are sections of DNA (deoxyribonucleic acid) that are found inside every human cell. They’re so tiny that they can be seen only under a powerful microscope. DNA is made of four chemicals that form pairs in different combinations. The combinations create codes for different genes. Each person has about 20,000 genes. The genes code for different traits, such as eye color, body type, or male or female sex.

What Is a Chromosome?

Inside each cell, DNA is tightly wrapped together in structures called chromosomes. Every normal cell has 23 pairs of chromosomes (for a total of 46):

  • 22 pairs of chromosomes are the same in males and females. These are called autosomes (AW-tuh-soamz).
  • The 23rd pair — the sex chromosomes — determines the sex of the baby. Females have two X chromosomes and males have one X chromosome and one Y chromosome.

DNA
Deoxyribonucleic acid (abbreviated DNA) is the molecule that carries genetic information for the development and functioning of an organism. DNA is made of two linked strands that wind around each other to resemble a twisted ladder — a shape known as a double helix. Each strand has a backbone made of alternating sugar (deoxyribose) and phosphate groups. Attached to each sugar is one of four bases: adenine (A), cytosine (C), guanine (G) or thymine (T). The two strands are connected by chemical bonds between the bases: adenine bonds with thymine, and cytosine bonds with guanine. The sequence of the bases along DNA’s backbone encodes biological information, such as the instructions for making a protein or RNA molecule.
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Biology Study Material

Is there a more amazing molecule than DNA? It makes each of us who we are. The more scientists understand it, the more we all understand ourselves, one another, and the world around us.   For example, did you know that we are all far more alike than we are different? In fact, the DNA from any two people is 99.9% identical, with that shared blueprint guiding our development and forming a common thread across the world.   The differing 0.1% contains variations that influence our uniqueness, which when combined with our environmental and social contexts give us our abilities, our health, our behavior.   How can one, single molecule contain so much mystery and wonder? We are only beginning to understand the answer to that question, which is what makes the study of DNA so exciting.

Is there a more amazing molecule than DNA? It makes each of us who we are. The more scientists understand it, the more we all understand ourselves, one another, and the world around us.   For example, did you know that we are all far more alike than we are different? In fact, the DNA from any two people is 99.9% identical, with that shared blueprint guiding our development and forming a common thread across the world.   The differing 0.1% contains variations that influence our uniqueness, which when combined with our environmental and social contexts give us our abilities, our health, our behavior.   How can one, single molecule contain so much mystery and wonder? We are only beginning to understand the answer to that question, which is what makes the study of DNA so exciting.

How Do Genes Pass From Parent to Child?

To form a fetus, an egg from the mother and sperm from the father come together. The egg and sperm each have one half of a set of chromosomes. The egg and sperm together give the baby the full set of chromosomes. So, half the baby’s DNA comes from the mother and half comes from the father. 1

CHAPTER 3

Lecture Topic 1.3.1

CO3Explain the basic of genetics that helps to identify and formulate problems 

Cell Division
 Cell division happens when a parent cell divides into two or more cells called daughter cells. Cell division usually occurs as part of a larger cell cycle. All cells reproduce by splitting into two, where each parental cell gives rise to two daughter cells.

These newly formed daughter cells could themselves divide and grow, giving rise to a new cell population that is formed by the division and growth of a single parental cell and its descendant.

In other words, such cycles of growth and division allow a single cell to form a structure consisting of millions of cells.

Types of Cell Division

There are two distinct types of cell division out of which the first one is vegetative division, wherein each daughter cell duplicates the parent cell called mitosis. The second one is meiosis, which divides into four haploid daughter cells.1

Mitosis: The process cells use to make exact replicas of themselves. Mitosis is observed in almost all the body’s cells, including eyes, skin, hair, and muscle cells.

Meiosis: In this type of cell division, sperm or egg cells are produced instead of identical daughter cells as in mitosis.

Binary Fission: Single-celled organisms like bacteria replicate themselves for reproduction.

Phases of the Cell Cycle (Biology Study Material)

There are two primary phases in the cell cycle:

  1. Interphase: This phase was thought to represent the resting stage between subsequent cell divisions, but new research has shown that it is a very active phase.
  2. M Phase (Mitosis phase): This is where the actual cell division occurs. There are two key steps in this phase, namely cytokinesis and karyokinesis.

The interphase further comprises three phases:

  1. G0 Phase (Resting Phase): The cell neither divides nor prepares itself for the division.
  2. G1 Phase (Gap 1): The cell is metabolically active and grows continuously during this phase.
  3. S phase (Synthesis): The DNA replication or synthesis occurs during this stage.
  4. G2 phase (Gap 2): Protein synthesis happens in this phase.
  5. Quiescent Stage (G0): The cells that do not undergo further division exits the G1 phase and enters an inactive stage. This stage is known as the quiescent stage (G0) of the cell cycle.

There are four stages in the M Phase, namely:

  1. Prophase
  2. Metaphase
  3. Anaphase
  4. Telophase
MeiosisMeiosis is a type of cell division that results in the formation of four daughter cells each with half the number of chromosomes as the parent cell.
MitosisMitosis is the type of cell division that results in the formation of two daughter cells each with the same number and kind of chromosomes as the parent cell.

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Introduction

In single-celled organisms, cell reproduction gives rise to the next generation. In multicellular organisms, cell division occurs not just to produce a whole new organism but for growth and replacement of worn-out cells within the organisms.

Cell division is always highly regulated and follows a highly orchestrated series of steps. The term cytokinesis refers to the division of a cell’s cytoplasm, while mitosis and meiosis refer to two different forms of nuclear division.

Mitosis results in two nuclei that are identical to the original nucleus. Meiosis, on the other hand, results in four nuclei, each having half the number of chromosomes of the original cell. In animals, meiosis only occurs in the cells that give rise to the sex cells (gametes), i.e., the egg and the sperm.

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Differences Between Mitosis and Meiosis

The important difference between mitosis and meiosis are mentioned below:

Difference between Mitosis and Meiosis
MitosisMeiosis
Interphase
Each chromosome replicates during the S phase of the interphase. The result is two genetically identical sister chromatids (However, do note that interphase is technically not a part of mitosis because it takes place between one mitotic phase and the next).Chromosomes not yet visible but DNA has been duplicated or replicated.
Prophase
Prophase –Each of the duplicated chromosomes appears as two identical or equal sister chromatids. The mitotic spindle begins to form. Chromosomes condense and thicken.Prophase I – crossing-over and recombination – Homologous chromosomes (each consists of two sister chromatids) appear together as pairs. Tetrad or bivalent is the structure that is formed. Segments of chromosomes are exchanged between non-sister chromatids at crossover points known as chiasmata (crossing-over).
Metaphase
Metaphase -The chromosomes assemble at the equator at the metaphase plate.Metaphase I – Chromosomes adjust on the metaphase plate. Chromosomes are still intact and arranged as pairs of homologues (bivalent).
Anaphase
Anaphase – The spindle fibres begin to contract. This starts to pull the sister chromatids apart. At the end of anaphase, a complete set of daughter chromosomes is found on each pole.Anaphase I – Sister chromatids stay intact. However, homologous chromosomes drift to the opposite or reverse poles.
Mode of Reproduction
Asexual ReproductionSexual Reproduction
Occurrence
All the cellsReproductive cells
Function
General growth and repair, Cell reproductionGenetic diversity through sexual reproduction
Cytokinesis
Occurs in TelophaseOccurs in Telophase I and in Telophase II
Discovered by
Walther FlemmingOscar Hertwig

Mitosis Overview

  • Mitosis is a continuous process of cell division which occurs in all types of living cells.
  • Mitosis involves four basic phases – prophase, metaphase, anaphase and telophase.
  • Mitosis is the process where the division of cell occurs by asexual reproduction.
  • In mitosis, the nuclear membrane is broken down, spindle fibres (microtubules) attach to the chromatids at the centromere and pull apart the chromatids.
  • When the chromatids reach separate ends of the cells, the spindle fibres disintegrate and a nuclear membrane rebuilds around the chromosomes making two nuclei.
  • Each nucleus is identical to the original nucleus as it was in G1 phase.

Also read: Difference between haploid and diploid

Meiosis Overview

  • Meiosis is the form of nuclear cell division that results in daughter cells that have one-half the chromosome numbers as the original cell.
  • In organisms that are diploid, the end result is cells that are haploid. Each daughter cell gets one complete set of chromosomes, i.e., one of each homologous pair of chromosomes.
  • In humans, this means the chromosome number is reduced from 46 to 23.
  • The germ cells undergo meiosis to give rise to sperm and eggs.
  • The joining together of a sperm and egg during fertilisation returns the number of the chromosomes to 46.
  • Cells that undergo meiosis go through the cell cycle, including the S phase, so the process begins with chromosomes that consist of two chromatids just as in mitosis.
  • Meiosis consists of meiosis I and meiosis II. In meiosis I, homologous chromosomes are separated into different nuclei.
  • This is the reduction division; chromosome number is divided in half. Meiosis II is very similar to mitosis; chromatids are separated into separate nuclei.
  • As in mitosis, it is spindle fibres that “pull” the chromosomes and chromatids apart in meiosis.
  • The end result of meiosis is four cells, each with one complete set of chromosomes instead of two sets of chromosomes.

Similarities Between Mitosis and Meiosis

  • Both mitosis and meiosis take place in the cell nuclei, which can be observed under a microscope.
  • Both mitosis and meiosis involve cell division.
  • Both the processes occur in the M-phase of the cell cycle. In both cycles, the typical stages are prophase, metaphase, anaphase and telophase.
  • In both cycles, synthesis of DNA takes place.

Lecture Topic 1.3.2

CO3Explain the basic of genetics that helps to identify and formulate problems 

Genetic disorders

What Is a Genetic Disorder?

A genetic disorder happens when a gene (or genes) has a problem with its code, and this causes a health problem. Sometimes a genetic disorder happens when a child inherits it from one or both parents. Other times, it happens only in the child (and the parents do not have the genetic disorder).

How Do Genetic Disorders Happen?

Different things can cause a genetic disorder, such as:

  • change (mutation) in one gene on a chromosome
  • a missing part of a chromosome (called a deletion)
  • genes shifting from one chromosome to another (called a translocation)
  • an extra or missing chromosome
  • too few or too many sex chromosomes

Genetic disorders are due to alterations or abnormalities in the genome of an organism. A genetic disorder may be caused by a mutation in a single gene or multiple genes. It can also be due to changes in the number or structure of chromosomes.

Genes are the basic unit of heredity. They hold the genetic information in the form of DNA which can be translated into useful proteins to carry out life processes. These genes undergo a mutation sometimes, which changes the instructions to formulate the protein, due to which the protein does not work properly. Such disorders are known as genetic disorders.

Some genetic disorders are innate, i.e., present by birth, while others are acquired due to mutations in a particular gene. The genetic disorders that are present by birth are inherited from parents, e.g. cystic fibrosis, haemophilia, sickle cell anaemia, etc. The genetic disorders that are acquired during the lifetime are not inherited from parents, these occur due to mutations that occur randomly or due to exposure to certain chemicals, environments or radiations such as cigarette smoke, UV radiations, etc. Cancer is one such disease.

The genetic disorders can be categorized into two types, namely Mendelian Disorders, i.e., a disorder in a single gene that follows Mendelian inheritance pattern, and Chromosomal Disorders, i.e., damage or alteration in the chromosomes structure or number, the chromosomes are either missing, duplicated or a part is translocated.

Types of Genetic Disorders

Mendelian Disorder

  • These disorders occur due to mutations in a single gene and can be easily detected by pedigree analysis.
  • These disorders can be autosomal dominant, autosomal recessive, sex-linked dominant, sex-linked recessive, and mitochondrial.

The most common Mendelian disorders include:

  • Cystic fibrosis (autosomal recessive)
  • Haemophilia (sex-linked recessive)
  • Albinism (autosomal recessive)
  • Sickle cell anaemia (autosomal recessive)

Chromosomal Disorder

  • These disorders are caused by any alteration in the number or structure of the chromosomes.
  • Sometimes the whole chromosome is gained or lost.
  • This type of disorder is usually fatal and affects many genes.

Some of the major chromosomal abnormalities are:

  • Down’s syndrome- the addition of a chromosome 21 (trisomy)
  • Turner’s syndrome-absence of an X chromosome (XO)
  • Kleinfelter’s syndrome-addition of an X chromosome (XXY)

List of Genetic Disorders

Following is the list of genetic disorders that occur in humans:

  1. Cystic fibrosis
  2. Thalassemia
  3. Huntington’s disease
  4. Hemochromatosis
  5. Turner’s syndrome
  6. Kleinfelter’s syndrome
  7. Leber’s Hereditary Optic Atrophy
  8. Cancer
  9. High Blood Pressure
  10. Obesity

Haemophilia

  • This is a type of sex-linked recessive disorders. According to the genetic inheritance pattern, the unaffected carrier mother passes on the haemophilic genes to sons.
  • It is a very rare type of disease among females because for a female to get the disease, the mother should either be hemophilic or a carrier but the father should be haemophilic.
  • This is a disorder in which blood doesn’t clot normally as the protein which helps in clotting of blood is affected. Therefore, a person suffering from this disease usually has symptoms of unexplained and excessive bleeding from cuts or injuries.
  • This type of genetic disorder is caused when the affected gene is located on the X chromosomes. Therefore, males are more frequently affected.

Sickle-cell anaemia

  • This is a type of autosomal recessive genetic disorder.
  • According to Mendelian genetics, its inheritance pattern follows inheritance from two carrying parents.
  • It is caused when the glutamic acid in the sixth position of the beta-globin chain of haemoglobin molecule is replaced by valine. The mutant haemoglobin molecule undergoes a physical change which changes the biconcave shape into the sickle shape.
  • This reduces the oxygen-binding capacity of the haemoglobin molecule.

Phenylketonuria

  • This genetic disorder is autosomal recessive in nature.
  • It is an inborn error caused due to the decreased metabolism level of the amino acid phenylalanine.
  • In this disorder, the affected person does not have the enzyme that converts phenylalanine to tyrosine. As a result, phenylalanine accumulation takes place in the body and is converted into many derivatives which result in mental retardation.

Thalassemia

  • This is a type of disorder in which the body makes an abnormal amount of haemoglobin. As a result, a large number of red blood cells are destroyed that leads to anaemia.
  • It is an autosomal recessive disease.
  • Facial bone deformities, abdominal swelling, dark urine are some of the symptoms of thalassemia.

Cystic Fibrosis

  • This is an autosomal recessive disorder.
  • This disease affects the lungs and the digestive system and the body produces thick and sticky mucus that blocks the lungs and pancreas.
  • People suffering from this disorder have a very short life-span.

Chromosomes are thread-like structure present in the nucleus that carries hereditary information in the form of genes which is passed from parents to offspring. Every species has a characteristic structure and number of chromosome present. Due to certain irregularities at the time of cell division, alteration in the structure or number of chromosomes may happen. Even the slightest alteration can lead to various abnormalities.

Chromosomal Disorders in Humans

Each human cell contains 46 (2n) chromosomes present as 23 pairs (n pairs), out of which 22 are autosomes and 1 pair of sex chromosomes.

Chromosomal disorders result from structural changes or numerical changes in chromosomes.

A. Chromosomal disorders due to numerical abnormalities

Chromosomal disorders are due to the change in the number of chromosomes present. This can be categorised into various types:

  • Aneuploidy: loss or gain of a chromosome. This happens due to non-disjunction of chromatids when chromatids fail to separate during cell division. This results in one gamete having two copies of one chromosome and the other having no chromosome.
    1. Trisomy: The cell has one extra chromosome (2n+1)
    2. Monosomy: The cell has one chromosome less (2n-1)

Aneuploidy can be due to nondisjunction of autosomes i.e. chromosomes 1-22 or sex chromosomes.

Chromosomal disorders due to aneuploidy: This is the cause of most of the genetically inherited disorders and abortion during pregnancy

  • Euploidy: Loss or gain of the whole set of chromosome. Mostly occurs in plants.
    • Haploid: Loss of one set of the chromosomes, i.e. ‘n’ number of chromosomes
    • Polyploid: Addition of one or more set of chromosomes, e.g. ‘3n (triploid)’, ‘6n (hexaploid)’ etc.

Lecture Topic 1.3.3

CO3Explain the basic of genetics that helps to identify and formulate problems 

In geneticscomplementation occurs when two strains of an organism with different homozygous recessive mutations that produce the same mutant phenotype (for example, a change in wing structure in flies) have offspring that express the wild-type phenotype when mated or crossed. Complementation will ordinarily occur if the mutations are in different genes (intergenic complementation). Complementation may also occur if the two mutations are at different sites within the same gene (intragenic complementation), but this effect is usually weaker than that of intergenic complementation. In the case where the mutations are in different genes, each strain’s genome supplies the wild-type allele to “complement” the mutated allele of the other strain’s genome. Since the mutations are recessive, the offspring will display the wild-type phenotype. A complementation test (sometimes called a “cis-trans” test) can be used to test whether the mutations in two strains are in different genes. Complementation ordinarily will occur more weakly or not at all if the mutations are in the same gene. The convenience and essence of this test is that the mutations that produce a phenotype can be assigned to different genes without the exact knowledge of what the gene product is doing on a molecular level. The complementation test was developed by American geneticist Edward B. Lewis.

If the combination of two genomes containing different recessive mutations yields a mutant phenotype, then there are three possibilities:

  1. Mutations occur in the same gene.
  2. One mutation affects the expression of the other.
  3. One mutation may result in an inhibitory product.

Example

For a simple example of a complementation test, suppose a geneticist is interested in studying two strains of white-eyed flies of the species Drosophila melanogaster, more commonly known as the common fruit fly. In this species, wild type flies have red eyes and eye color is known to be related to two genes, A and B. Each one of these genes has two alleles, a dominant one that codes for a working protein (A and B respectively) and a recessive one that codes for a malfunctioning protein (a and b respectively). Since both proteins are necessary for the synthesis of red pigmentation in the eyes, if a given fly is homozygous for either a or b, it will have white eyes.

Knowing this, the geneticist may perform a complementation test on two separately obtained strains of pure-breeding white-eyed flies. The test is performed by crossing two flies, one from each strain. If the resulting progeny have red eyes, the two strains are said to complement; if the progeny have white eyes, they do not.

If the strains complement, we imagine that one strain must have a genotype aa BB and the other AA bb, which when crossed yield the genotype AaBb. In other words, each strain is homozygous for a different deficiency that produces the same phenotype. If the strains do not complement, they both must have genotypes aa BB, AA bb, or aa bb. In other words, they are both homozygous for the same deficiency, which obviously will produce the same phenotype1

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