Patna university Ph.D. question answer?

1@.  give an account of the parental care in amphibians?

Answer:- Parental care in amphibians can vary greatly depending on the species. Some species of amphibians are known to be excellent parents, while others provide little to no care for their offspring. One of the most well-known examples of parental care in amphibians is seen in certain species of frogs. For example, some species of tree frogs will lay their eggs in a foam nest that the male guards. In some cases, the male will even physically carry the eggs on his back until they hatch. Once the tadpoles hatch, some species of frogs will continue to care for their offspring by carrying them to a body of water where they can feed and grow. Another example of parental care in amphibians can be seen in salamanders. Some species of salamanders will lay their eggs in a damp location, such as a log or under a rock, and then guard the eggs until they hatch. In some species, the male will even stay with the eggs and provide protection from predators. However, not all species of amphibians provide care for their offspring. For example, many species of toads will lay their eggs in a pond or stream and then abandon them. The tadpoles must fend for themselves, with no protection or assistance from their parents. In conclusion, the level of parental care in amphibians can vary greatly depending on the species. While some species are known to provide excellent care for their offspring, others provide little to no care. 

 2@.  Give an account of transport of substances across the plasma membrane.

Answer:- The transport of substances across the plasma membrane is a vital process for cells to maintain their homeostasis and to exchange materials with their surroundings. There are several mechanisms by which substances can cross the plasma membrane, including:

1.    Simple Diffusion: This is the passive movement of molecules from an area of high concentration to an area of low concentration until an equilibrium is reached. This process requires no energy input and can occur for both small and lipid-soluble molecules.

2.    Facilitated Diffusion: This is a passive process similar to simple diffusion, but facilitated diffusion requires the assistance of transport proteins to move molecules across the membrane. These proteins form channels or pumps that allow the passage of specific molecules, such as glucose and ions, to diffuse across the membrane.

3.    Osmosis: This is the diffusion of water molecules across a selectively permeable membrane from an area of high concentration to an area of low concentration. This process is crucial in maintaining the balance of water and solute concentration within cells.

Active Transport: This is the movement of substances against their concentration gradient, from an area of low concentration to an area of high concentration. This process requires energy input in the form of ATP and is mediated by transport proteins, such as ion pumps and carriers, which pump molecules across the membrane against their gradient. In summary, the transport of substances across the plasma membrane is a complex process that is regulated by various mechanisms, including diffusion, facilitated diffusion, osmosis, and active transport. These mechanisms ensure that cells can take up necessary nutrients, excrete waste products, and maintain their internal environment. Regenerate response

 

3@. Describe the principle and working of transmission electron microscope.

Answer:- The transmission electron microscope (TEM) is an advanced scientific instrument that utilizes electron beam to produce high-resolution images of the internal structure of materials. The TEM works based on the principle of electron transparency, which states that electrons can pass through thin samples without significant scattering or absorption. The working of TEM can be described as follows:

1.    Electron source: The TEM has a high-brightness electron source, typically a thermionic cathode or a field-emission tip, which produces a stream of electrons.

2.    Electron gun: The electron gun consists of electron lenses that focus and collimate the electron beam into a fine probe. The electron gun also contains electrostatic or magnetic lenses to control the beam's energy and focal length.

3.    Sample holder: The sample is placed on a holder in the TEM column and is located in the path of the electron beam. The sample must be thin enough (typically less than 100 nanometers) to allow electrons to pass through it.

4.    Specimen chamber: The specimen chamber is maintained at high vacuum to prevent electron scattering by gas molecules.

5.    Electron lenses: Electron lenses are used to focus and manipulate the electron beam as it passes through the sample. These lenses include magnetic or electrostatic lenses, which control the beam's energy and focal length.

6.    Detector: The electrons that pass through the sample are collected by a detector, such as a CCD camera or a scintillation screen, which produces an image of the sample's internal structure.

Image analysis: The image produced by the TEM is then analyzed to obtain information about the sample's structure, composition, and properties. In conclusion, the TEM works by producing a beam of electrons, which pass through a thin sample, and the electrons that pass through are collected by a detector to form an image of the sample's internal structure. The high-resolution images obtained by TEMs are used in many scientific and industrial applications, including materials science, biology, and nanotechnology.

 

4@.  With the help of diagram describe the cleavage pattern in frog.

Answer:- The cleavage pattern in frogs is characterized by radial symmetry, meaning that the cells divide in a manner that is evenly spaced around a central axis. This pattern is known as holoblastic cleavage and results in the formation of a ball of cells, called a blastula, that undergoes further development to form the various tissues and organs of the frog. In the early stages of cleavage, the zygote (the fertilized egg) divides into two cells, which then divide into four, and so on. The cells are arranged in a regular pattern, with each division resulting in cells that are positioned equidistant from one another. The following diagram illustrates the cleavage pattern in frogs:

    O O O O

   / \ / \ / \ /
O O O O O O O

In this diagram, the "O" represents the cells produced during each round of cleavage. As the number of cells increases, they begin to differentiate and form the various tissues and organs of the developing frog. The precise timing and pattern of these subsequent developmental events are regulated by complex molecular and cellular processes, but the radial symmetry established during cleavage provides a strong foundation for the organization of the developing embryo.

 

5@. Give an account of hypothalamic control of pituitary secretion.

Answer:- The hypothalamus, located in the brain, plays a critical role in regulating pituitary gland secretion. The hypothalamus releases various hormones, called releasing or inhibitory hormones, into a capillary network that surrounds the pituitary gland, called the hypothalamic-pituitary portal system. These hormones then travel through the portal system to reach the anterior pituitary, where they stimulate or inhibit the release of pituitary hormones.

The hypothalamic-pituitary-adrenal axis (HPA) is a major hypothalamic control system that regulates the secretion of pituitary hormones, particularly cortisol from the adrenal gland. The HPA axis is activated by stress, leading to the release of corticotropin-releasing hormone (CRH) from the hypothalamus, which stimulates the release of adrenocorticotropin hormone (ACTH) from the anterior pituitary. ACTH then stimulates the adrenal gland to release cortisol.

The hypothalamic-pituitary-gonadal (HPG) axis controls the secretion of gonadotropins (Luteinizing Hormone - LH, and Follicle-Stimulating Hormone - FSH) from the anterior pituitary, which regulate the function of the gonads (ovaries or testes). The hypothalamus releases gonadotropin-releasing hormone (GnRH) in a pulsatile manner, which stimulates the release of LH and FSH from the pituitary. This axis is responsible for regulating the menstrual cycle in females and spermatogenesis in males.

In addition to the HPA and HPG axes, the hypothalamus also regulates the secretion of thyrotropin-releasing hormone (TRH), which stimulates the release of thyroid-stimulating hormone (TSH) from the anterior pituitary. TSH then regulates the secretion of thyroid hormones from the thyroid gland.

In summary, the hypothalamus exerts control over the pituitary gland by releasing hormones that stimulate or inhibit the release of pituitary hormones, which in turn regulate the secretion of hormones from other endocrine glands. This system is critical for maintaining homeostasis and coordinating the actions of the endocrine system.

 

6@. Describe the stages and checkpoints in cell cycle.

Answer:- The cell cycle is the series of events that cells go through as they grow and divide. It is divided into two main stages: interphase (G1, S, G2) and the M phase (Mitosis).

1.    Interphase:

·         G1 phase: During this stage, the cell grows and carries out normal cellular functions. At the end of this stage, the cell checks for any DNA damage and if it's damaged, the cell may halt its progression to the next stage and initiate DNA repair mechanisms.

·         S phase: During this stage, DNA replication takes place, resulting in an exact copy of the genetic material.

·         G2 phase: During this stage, the cell checks for any remaining DNA damage and prepares for mitosis. If DNA damage is present and cannot be repaired, the cell may undergo apoptosis (programmed cell death).

2.    M phase (Mitosis): During this stage, the cell physically divides into two genetically identical daughter cells. This is further divided into several stages: Prophase, Metaphase, Anaphase, Telophase and Cytokinesis.

Checkpoints:

·         G1 checkpoint: A critical control point that ensures that the cell has sufficient nutrients, energy, and DNA integrity before entering the next stage.

·         G2 checkpoint: This checkpoint ensures that DNA replication is complete and no DNA damage is present before the cell can enter mitosis.

M checkpoint: This checkpoint ensures that the chromosomes are properly aligned on the spindle fibers before being separated during Anaphase.

 

 

7@. Describe the biosynthesis of urea.

 

Answer:-  Urea is synthesized in the liver from the waste products of protein metabolism, specifically from the amino acid nitrogen that is produced from the breakdown of excess amino acids. The biosynthesis of urea involves several steps:

1.    Ammonia production: In the liver, the amino groups from excess amino acids are converted to ammonia (NH3) by the enzyme amino acid dehydrogenase. Ammonia is toxic to cells, so it must be rapidly converted to a less toxic substance.

2.    Conversion of ammonia to carbamoyl phosphate: The ammonia produced in the first step is converted to carbamoyl phosphate by the enzyme carbamoyl phosphate synthetase. This reaction consumes ATP and requires the presence of bicarbonate (HCO3-) and a nitrogen source (ammonia).

3.    Synthesis of citrulline: The carbamoyl phosphate from the second step is combined with ornithine, another molecule produced in the liver, by the enzyme ornithine transcarbamylase to form citrulline.

4.    Conversion of citrulline to argininosuccinate: The citrulline formed in the third step is converted to argininosuccinate by the enzyme argininosuccinate synthetase.

5.    Conversion of argininosuccinate to arginine: Argininosuccinate is cleaved by the enzyme argininosuccinate lyase to form arginine and fumarate.

6.    Conversion of arginine to urea: The arginine produced in the fifth step is converted to urea by the enzyme arginase. This reaction occurs in the liver and consumes a molecule of water (H2O), producing urea and ornithine.

The urea produced in the liver is then transported in the blood to the kidneys, where it is filtered and excreted in the urine, helping to eliminate the waste products of protein metabolism from the body.

 

8@. Give an account of nitrogen cycle in nature.

 

Answer:- The nitrogen cycle is a biogeochemical process that describes the movement of nitrogen and its various forms through the environment and the biosphere. The cycle can be divided into several steps, each of which plays a role in the conversion of nitrogen from one form to another. The steps in the nitrogen cycle include:

1.    Nitrogen Fixation: The process by which nitrogen gas (N2) from the atmosphere is converted into a form that can be used by plants and animals. This process is performed by certain bacteria, such as Rhizobia and Azotobacter, which live in the soil or in symbiotic relationships with plants.

2.    Ammonification: The process by which organic nitrogen compounds are broken down into simpler compounds, such as ammonia (NH3), by bacteria and fungi in the soil.

3.    Nitrification: The process by which ammonia is converted into nitrite (NO2-) and then into nitrate (NO3-) by bacteria in the soil.

4.    Assimilation: The process by which plants take up nitrates from the soil and incorporate them into organic compounds, such as amino acids, nucleotides, and chlorophyll.

5.    Denitrification: The process by which bacteria in the soil convert nitrates back into nitrogen gas, releasing it back into the atmosphere.

6.    Deposition: The process by which nitrogen is deposited back into the soil or the ocean by rain and other precipitation.

These processes are constantly taking place in the environment and are crucial to the health of ecosystems, as they help to maintain a balance of nitrogen in the biosphere. The nitrogen cycle also plays an important role in the production of food and fiber, as nitrogen is a key component of the compounds needed for plant growth.

 

9@. Describe the ultrastructure of skeletal muscle in the related and contracted stage.

Answer:- The ultra structure of skeletal muscle refers to its microscopic anatomy, including the arrangement of individual muscle fibers and their component parts. In a relaxed state, the sarcomeres, the basic functional units of skeletal muscle fibers, are elongated and not contracted.

In a contracted state, the sarcomeres shorten and produce force. The sarcomeres consist of thin filaments made up of actin and thick filaments made up of myosin. These filaments overlap and interact to produce movement of the sarcomere. When an action potential reaches the muscle fiber, calcium ions are released into the sarcoplasm, activating the myosin heads which then bind to the actin filaments and produce cross-bridge cycling, leading to shortening of the sarcomere and contraction of the muscle fiber.

Additionally, the sarcoplasmic reticulum, a network of membranous tubules that surrounds the myofibrils, plays an important role in regulating the level of calcium ions in the sarcoplasm, ensuring smooth and coordinated contraction of the muscle fibers. The T-tubules, deep invaginations of the sarcolemma, allow for rapid spread of the action potential throughout the muscle fiber, leading to synchronous contraction of all the sarcomeres within the fiber.

In summary, the ultra structure of skeletal muscle in the contracted state is characterized by shortened sarcomeres, activated cross-bridge cycling between actin and myosin filaments, regulated calcium ion levels, and synchronized contraction of the sarcomeres within the muscle fiber.

 

10@. how are respiratory gases (O2 and CO2) transported by blood in vertebrates from lungs to tissue and back.

 

Answer:- In vertebrates, oxygen and carbon dioxide are transported in the blood by red blood cells. Oxygen is carried from the lungs to the tissues in the form of oxygen bound to hemoglobin (Hb), a protein found in red blood cells. Hemoglobin has a high affinity for oxygen and readily binds to it in the lungs, where the oxygen partial pressure is high.

As the blood circulates through the body, the oxygen-rich hemoglobin releases oxygen to the tissues, where the oxygen partial pressure is lower. The oxygen is then used by the cells for cellular respiration to produce energy.

Carbon dioxide is produced as a byproduct of cellular respiration and is transported from the tissues to the lungs in three forms: as bicarbonate ions (HCO3-), as dissolved CO2, and as carbamino compounds (CO2 bound to hemoglobin).

Bicarbonate ions are produced when carbon dioxide reacts with water in the blood to form carbonic acid (H2CO3), which then dissociates into bicarbonate and hydrogen ions (H+). The bicarbonate ions are carried in the blood to the lungs, where they combine with hydrogen ions to reform carbonic acid, which then dissociates into carbon dioxide and water. The carbon dioxide then diffuses from the blood into the lungs, where it is exhaled.

Dissolved CO2 is also carried in the blood to the lungs, where it diffuses into the air and is exhaled.

Carbamino compounds are formed when carbon dioxide binds to hemoglobin in the blood, reducing its affinity for oxygen. The carbamino compounds are carried to the lungs, where the carbon dioxide is released and exhaled.

In summary, respiratory gases are transported from the lungs to the tissues and back by blood in a complex process that involves several different forms and mechanisms, but is ultimately driven by the difference in oxygen and carbon dioxide partial pressures between the lungs and the tissues.

 

11@. give an account of the parental care of amphibians.

 

Answer:- Amphibians have a diverse range of reproductive strategies, and the level of parental care they provide can vary greatly between species. Some species of amphibians are known to exhibit no parental care, while others show significant investment in the protection and care of their offspring.

One of the most common forms of parental care in amphibians is the deposition of eggs in water. Some species of frogs and toads will lay their eggs in water and then abandon them, providing no further care for their offspring. Other species, however, will defend the eggs or tadpoles from predators and provide them with additional resources such as food or protection from environmental stressors.

Some species of amphibians, such as certain types of frogs and salamanders, carry their eggs or tadpoles on their bodies and provide them with direct protection and care. For example, some species of frogs will carry their eggs on their hind legs, keeping them moist and safe from predators until they hatch into tadpoles. In some cases, the tadpoles will continue to live on the parent's body after hatching, receiving protection and nourishment until they are ready to survive on their own.

Other species of amphibians, such as some species of newts and salamanders, provide care for their offspring even after they have hatched and become juvenile animals. For example, some species of newts will guard their young and even feed them directly by regurgitation.

In conclusion, the extent of parental care in amphibians can vary greatly between species, but many species do exhibit some form of care for their offspring, ranging from the deposition of eggs in water to direct protection and feeding of juvenile animals.

 

12@. Describe the structure and function of different types of antibody.

 

Answer:- Antibodies are proteins that play a crucial role in the immune system, serving as a defense against pathogens such as bacteria and viruses. They are produced by B cells, which are a type of white blood cell. There are five main classes of antibodies, each with a unique structure and function:

1.    IgM: This is the largest antibody and is the first to be produced in response to an infection. It is found in the blood and other bodily fluids and is effective against a wide range of pathogens.

2.    IgG: This is the most abundant antibody in the blood and is the primary antibody involved in secondary immune responses. It is able to cross the placenta, providing protection to the developing fetus.

3.    IgA: This antibody is found in secretions such as saliva, tears, and breast milk and is important for protecting mucosal surfaces, such as the gut and respiratory tract, from pathogens.

4.    IgD: This antibody is found on the surface of B cells and is involved in the activation of these cells, but its exact function is not well understood.

5.    IgE: This antibody is involved in allergy and asthma, and is responsible for the release of histamine and other chemicals that cause symptoms such as itching, redness, and swelling.

Each antibody is made up of four protein chains, two heavy chains and two light chains, held together by disulfide bonds. The variable region of the heavy and light chains determines the specificity of the antibody, allowing it to bind to specific antigens (foreign substances) and mark them for destruction by other components of the immune system.

 

13@. describe the different causes of air pollution.

 

Answer:- Air pollution is caused by a variety of factors, both natural and human-made. Some of the main causes of air pollution include:

1.    Industrial emissions: Industries such as manufacturing, mining, and construction emit a significant amount of pollutants into the air. These pollutants can include particulate matter, nitrogen oxides, and sulfur dioxide.

2.    Vehicle emissions: Cars, trucks, and other vehicles emit a significant amount of air pollutants, including carbon monoxide, nitrogen oxides, and particulate matter.

3.    Agricultural practices: Agricultural activities, such as the use of fertilizers and pesticides, can emit pollutants into the air, including ammonia and methane.

4.    Natural events: Natural events such as wildfires, volcanic eruptions, and dust storms can also contribute to air pollution.

5.    Household activities: Household activities such as cooking, heating, and using certain products such as cleaning agents and personal care products, can emit pollutants into the air.

6.    Waste management: Landfills, wastewater treatment plants, and waste incineration facilities emit pollutants into the air, including methane and dioxins.

Overall, air pollution is a complex problem with multiple sources and causes. Addressing it requires a combination of measures, such as reducing emissions from industry and transportation, improving energy efficiency, and promoting sustainable practices in agriculture and waste management.

 

14@. Describe the ovarian follicular growth and differentiation in an eutherian mammal. 

 

Answer:- The ovarian follicular growth and differentiation in eutherian mammals is a complex process that is regulated by various hormones and growth factors.

Folliculogenesis is the process by which ovarian follicles develop and mature in the ovary. It begins with a primary oocyte (the female germ cell) surrounded by a single layer of squamous granulosa cells. Over time, the primary oocyte increases in size, and the surrounding granulosa cells differentiate and multiply to form a multilayered follicle.

During the early stages of folliculogenesis, follicles are referred to as primordial follicles. As the follicles continue to develop, they enter a stage known as the primary follicle stage. At this stage, the granulosa cells surrounding the oocyte secrete increasing amounts of follicle-stimulating hormone (FSH) receptor, which allows them to respond to FSH from the anterior pituitary gland. This FSH stimulates further growth and differentiation of the follicle, leading to the formation of a secondary follicle.

As the follicle enters the secondary stage, the granulosa cells begin to secrete estrogens, which cause the theca cells (the outer layer of cells surrounding the granulosa cells) to differentiate and produce androgens. The androgens are then converted to estrogens by the granulosa cells, amplifying the levels of estrogens in the follicle. This increased estrogen secretion stimulates the anterior pituitary gland to secrete increasing amounts of luteinizing hormone (LH), leading to the final stage of folliculogenesis: the preovulatory stage.

During the preovulatory stage, the granulosa cells undergo luteinization and form the corpus luteum. The corpus luteum secretes high levels of progesterone and estrogens, which play critical roles in preparing the uterus for implantation and maintaining pregnancy. If pregnancy does not occur, the corpus luteum regresses and the levels of progesterone and estrogens decrease, leading to the onset of a new menstrual cycle.

In conclusion, the growth and differentiation of ovarian follicles in eutherian mammals is a complex process that is regulated by various hormones and growth factors, ultimately leading to the formation of a mature follicle capable of ovulating and supporting pregnancy.

 

15@. Give an account of somatic cell hybridization.

 

Answer:- Somatic cell hybridization is a technique used to create hybrid cells, or cells that contain the genetic material from two different organisms. It is a process that combines cells from two different species or two different individuals in order to study the properties and functions of the resulting cells.

The process of somatic cell hybridization typically begins by growing cells from the two different organisms in culture. These cells are then fused together using various methods, such as electrical stimulation, chemical agents, or physical pressure. The fused cells are then grown in culture to form hybrid cells, which contain the genetic material from both of the parent cells.

The resulting hybrid cells can be used for a variety of purposes, such as studying the properties of specific genes, exploring the interactions between different genes, and determining the functions of specific proteins. In addition, hybrid cells can be used to study the processes of cell division and differentiation, as well as to develop new therapies for genetic diseases.

Somatic cell hybridization has contributed greatly to our understanding of genetics and has helped to establish many of the fundamental principles of molecular biology. It has also provided important tools for the study of diseases, including cancer, and has played a key role in the development of new therapies for these diseases.

 

16@. Describe in brief transcription and post transcription modification of mRNA in an eukaryotic.

 

Answer:- Transcription is the process by which the genetic information stored in DNA is converted into RNA, a molecule that can be used to direct the synthesis of proteins. In eukaryotes, transcription takes place in the nucleus and is carried out by the RNA polymerase II enzyme. The DNA double helix unwinds and the RNA polymerase reads the sequence of nucleotides along one strand of the DNA and synthesizes a complementary RNA molecule.

Post-transcriptional modification refers to a series of modifications that occur after transcription but before the mRNA is translated into a protein. These modifications play a critical role in regulating gene expression and ensuring proper protein function. Some common post-transcriptional modifications in eukaryotes include capping, splicing, and polyadenylation.

Capping refers to the addition of a modified nucleotide called a "cap" to the 5' end of the mRNA molecule. The cap helps protect the mRNA from degradation and also serves as a signal for the ribosome to begin translation.

Splicing is the process by which non-coding sequences called introns are removed and exons are joined together to form a mature mRNA molecule. This allows a single gene to encode multiple different proteins.

Polyadenylation refers to the addition of a long string of adenine nucleotides called a "poly(A) tail" to the 3' end of the mRNA molecule. The poly(A) tail helps protect the mRNA from degradation and also affects its stability and transport out of the nucleus.

Together, these post-transcriptional modifications play a crucial role in regulating gene expression and determining the final function of a protein.

 

17@. Describe gross and functional anatomy of kidney tubules of a mammal and the mechanism of urine formation.

 

Answer :- The kidneys of mammals are complex organs that play a critical role in maintaining fluid and electrolyte balance, removing waste products from the blood, and regulating blood pressure. One of the key structures within the kidney is the tubule, which is responsible for the formation of urine.

The gross anatomy of a kidney tubule in a mammal includes several segments, each with a specific function. The tubule begins at the renal corpuscle, which filters the blood. The filtrate then moves through the proximal tubule, where various solutes and water are reabsorbed into the bloodstream. The next segment is the Loop of Henle, which helps to create a steep concentration gradient of ions in the renal medulla, leading to the formation of a concentrated urine. The distal tubule and collecting duct then reabsorb additional ions and water, before finally delivering the urine to the renal pelvis, from where it flows into the ureter and ultimately the bladder.

The mechanism of urine formation within the kidney tubules can be described as a series of steps, each of which serves to concentrate or dilute the filtrate. The first step is filtration at the renal corpuscle, where blood is filtered through the glomerulus into Bowman's capsule. This filtrate contains ions, organic molecules, and water, but does not contain blood cells or large proteins.

The next step is reabsorption in the proximal tubule, where the tubular cells actively transport ions and other substances from the filtrate back into the bloodstream. This reabsorption process helps to conserve useful substances, such as glucose and amino acids, and to regulate the overall composition of the filtrate.

The Loop of Henle, which descends into the renal medulla, then helps to create a concentration gradient by allowing ions to diffuse out of the tubule and into the surrounding interstitial fluid. The distal tubule and collecting duct then reabsorb additional ions and water, depending on the body's needs, and secrete others, such as potassium, to further adjust the composition of the filtrate.

Finally, the urine flows from the collecting ducts into the renal pelvis, and from there into the ureter and bladder, where it is eliminated from the body. This entire process serves to regulate fluid and electrolyte balance, remove waste products from the blood, and maintain overall health.

 

18@. Define hypersensitivity classify hypersensitivity reactions as proposed by gell and coombs, giving important information regarding each type.

 

Answer:- Hypersensitivity reactions are a group of pathological responses of the immune system to normally harmless substances. Hypersensitivity reactions can be classified into four types, as proposed by Gell and Coombs:

1.    Type I hypersensitivity (Immediate Hypersensitivity) - This type of reaction is also known as anaphylaxis or anaphylactic reaction. It is characterized by a rapid and severe response to an allergen, such as pollen, food, insect stings, or drugs. Symptoms include itching, hives, redness, swelling, shortness of breath, and in severe cases, shock and loss of consciousness. This type of reaction is mediated by IgE antibodies.

2.    Type II hypersensitivity (Cytotoxic Hypersensitivity) - This type of reaction is characterized by the direct attack of cells by antibodies. It is most commonly associated with autoimmune diseases, such as hemolytic anemia, where the immune system mistakenly attacks its own red blood cells.

3.    Type III hypersensitivity (Immune Complex Hypersensitivity) - This type of reaction is characterized by the formation of antigen-antibody complexes in the bloodstream, which can deposit in different tissues and cause inflammation and tissue damage. Examples include serum sickness, a condition caused by the injection of foreign proteins, and lupus nephritis, a type of kidney disease seen in patients with systemic lupus erythematosus.

4.    Type IV hypersensitivity (Delayed Hypersensitivity) - This type of reaction is characterized by a delayed onset, usually several hours to 2 days after exposure to an allergen. It is mediated by T-lymphocytes and is often seen in contact dermatitis, where the skin becomes red, swollen and itchy after contact with an allergen, such as poison ivy.

It is important to note that these classifications are not mutually exclusive and that some hypersensitivity reactions may involve more than one mechanism. Additionally, some reactions may be difficult to classify, as they may involve a combination of mechanisms.

 

19@. Explain hardy-Weinberg principle of genetics equilibrium and its mathematical derivation.

 

Answer:- The Hardy-Weinberg principle, also known as the Hardy-Weinberg equilibrium, is a theoretical model in population genetics that describes the distribution of genetic variants in a population. It provides a baseline against which observed frequencies of genetic variants can be compared and provides a way to test whether observed frequencies deviate from expectations due to factors such as mutation, selection, migration, or genetic drift.

The Hardy-Weinberg principle states that, in a large and random mating population, the frequency of alleles (versions of a gene) and the frequency of genotypes (combinations of alleles) will remain constant from one generation to the next in the absence of other influences. This can be expressed mathematically as follows:

Let p and q be the frequencies of two alleles (A and a) at a single gene locus. The frequency of the dominant allele (A) is represented by p and the frequency of the recessive allele (a) is represented by q. The frequency of the homozygous dominant genotype (AA) is then p^2, the frequency of the heterozygous genotype (Aa) is 2pq, and the frequency of the homozygous recessive genotype (aa) is q^2. The sum of these three frequencies must equal 1:

p^2 + 2pq + q^2 = 1

This equation states that the frequency of all possible genotypes at a single locus must add up to

1.In a population that is in Hardy-Weinberg equilibrium, the frequencies of alleles and genotypes will remain constant over time unless influenced by factors such as mutation, selection, migration, or genetic drift. Any deviations from Hardy-Weinberg expectations can be used to infer the presence and impact of such factors on the population.

 

20@. Describe in brief the destabilizing forces of genetic equilibrium.

 

Answer :- Genetic equilibrium refers to a state in which the frequency of alleles (versions of a gene) in a population remains stable over time, with no net change in the distribution. However, there are several factors that can disturb this equilibrium and cause a shift in the frequency of alleles, leading to evolution. These factors are known as destabilizing forces and include:

1.    Mutations: Mutations are changes in the DNA sequence that can introduce new alleles into the population, altering the frequency of existing alleles.

2.    Gene flow: Gene flow refers to the movement of individuals or gametes (reproductive cells) into or out of a population, introducing new alleles or reducing the frequency of existing ones.

3.    Genetic drift: Genetic drift is a random fluctuation in the frequency of alleles in a small population, leading to a loss of genetic diversity and potentially altering the distribution of alleles.

4.    Natural selection: Natural selection is the process by which individuals with advantageous traits are more likely to survive and reproduce, leading to an increase in the frequency of those traits in the population.

Each of these factors can play a role in shifting the genetic equilibrium of a population and contribute to its evolution over time.

 

21@. give an brief account of the various steps of protein synthesis in an eukaryotic cell.

 

Answer: - Protein synthesis in eukaryotic cells involves the following steps:

1.    Transcription: This is the first step of protein synthesis and it takes place in the nucleus. During transcription, a portion of DNA is copied into a molecule of messenger RNA (mRNA) by an enzyme called RNA polymerase. This mRNA molecule carries the genetic information from the DNA to the cytoplasm.

2.    Transport of mRNA to the cytoplasm: After being synthesized, the mRNA molecule leaves the nucleus and travels to the cytoplasm.

3.    Translation: This is the process by which the genetic information stored in the mRNA is used to assemble a protein. The mRNA molecule binds to a ribosome, which acts as a platform for the formation of the protein. Transfer RNA (tRNA) molecules bring individual amino acids to the ribosome, where they are assembled into a growing protein chain according to the sequence specified by the mRNA.

4.    Initiation: The process of initiation starts when the ribosome recognizes the start codon of the mRNA. This codon is usually AUG, which codes for the amino acid methionine.

5.    Elongation: In this step, the ribosome moves along the mRNA molecule and adds new amino acids to the growing protein chain. This process continues until a stop codon is reached.

6.    Termination: The ribosome recognizes the stop codon, causing the ribosome to release the newly formed protein and dissociate from the mRNA.

7.    Post-translational modifications: After being synthesized, the protein may undergo further modifications, such as cleavage of its signal peptide, folding into its final 3-dimensional structure, and the addition of chemical groups.

These steps of protein synthesis are essential for the proper functioning of a eukaryotic cell and the organism as a whole.