MHT CET 2024 30 April Shift 1 Question Paper (Available): Download PCB Question Paper with Answers PDF

Roan cattle exhibit a coat color pattern where both red and white hairs are visible and fully expressed, making it a classic case of codominance. In codominance, both alleles in a heterozygous organism are equally expressed, without blending, resulting in a phenotype that simultaneously shows both traits.

For instance, in roan cattle, the red allele expresses red hairs, and the white allele expresses white hairs, leading to a mixture of red and white on the coat. Neither allele is recessive, and both contribute to the phenotype equally.

Conclusion: Roan cattle are an example of codominance, where both alleles are equally and visibly expressed.

The Ti (tumor-inducing) plasmid is a naturally occurring plasmid found in the bacterium Agrobacterium tumefaciens. This bacterium uses the Ti plasmid to transfer a specific DNA segment into plant cells, leading to the formation of crown gall tumors.

In genetic engineering, the tumor-inducing genes on the Ti plasmid are replaced with desired genes, enabling scientists to introduce beneficial traits into plants, such as pest resistance or improved nutritional content.

Conclusion: The Ti plasmid, obtained from Agrobacterium tumefaciens, is widely used in genetic engineering to modify plant genomes.

Root pressure is a mechanism in plants that helps move water from roots to shoots, particularly when transpiration rates are low. It is generated by the active transport of ions into the root xylem, which lowers the water potential. As a result, water enters the xylem through osmosis, creating a positive pressure that pushes water upwards.

This process is significant during the early morning or at night when transpiration is minimal, ensuring that plants maintain hydration and nutrient flow. However, root pressure is insufficient for water transport in tall plants, where transpiration pull plays a dominant role.

Conclusion: Root pressure is a vital mechanism that helps in the upward movement of water during low transpiration conditions.

The prostate gland is a key component of the male reproductive system. It secretes a fluid that forms part of the semen. This fluid contains enzymes and nutrients essential for sperm health and motility. One of its major components is prostate-specific antigen (PSA), which helps liquefy semen, making it easier for sperm to travel.

The prostate gland also contains smooth muscle fibers that assist in propelling semen during ejaculation. Other options are incorrect because the prostate does not produce insulin (a function of the pancreas), regulate calcium levels (handled by the parathyroid glands), or filter blood (a role of the kidneys).

Conclusion: The prostate gland secretes fluid that nourishes and supports sperm, which is vital for male fertility.

Human embryonic development follows a specific sequence of stages:

Morula: Formation of a solid ball of cells resulting from repeated divisions of the zygote.

Blastocyst: The morula develops a fluid-filled cavity, leading to the formation of the blastocyst, which implants in the uterine wall.

Gastrulation: Formation of the three germ layers (ectoderm, mesoderm, and endoderm), which lay the groundwork for all major organs.

Neurulation: Development of the neural tube, which becomes the central nervous system.

Conclusion: The accurate sequence of human embryo development stages is Morula → Blastocyst → Gastrulation → Neurulation.

When the substrate concentration is increased, the reaction rate initially rises because more substrate molecules bind to the enzyme's active sites, forming more enzyme-substrate complexes. However, this increase continues only until all active sites on the enzyme are saturated.

Beyond this saturation point, adding more substrate does not affect the reaction rate, as the enzyme operates at its maximum velocity (Vmax).

Equation: Rate of reaction = (Vmax [S]) / (Km + [S])

Here, Km is the substrate concentration at which the reaction rate is half of Vmax.

Conclusion: The reaction rate increases with substrate concentration until the enzyme becomes saturated, after which the rate plateaus.

The neurohypophysis, also known as the posterior pituitary, is primarily involved in the storage and release of hormones like oxytocin and vasopressin. It consists of:

Pars nervosa: The main region responsible for hormone release.

Median eminence: A connection point between the hypothalamus and the pituitary gland.

Infundibular stalk: The bridge connecting the hypothalamus to the posterior pituitary.

The pars distalis, however, is part of the adenohypophysis (anterior pituitary) and is not associated with the neurohypophysis.

Conclusion: Pars distalis belongs to the anterior pituitary and is not a part of the neurohypophysis.

Abscisic acid (ABA) is a plant hormone that inhibits growth by suppressing processes like cell elongation and division. It plays a vital role in:

- Inducing seed dormancy to prevent germination under unfavorable conditions.

- Regulating stomatal closure to conserve water during drought.

- Inhibiting shoot and root growth to conserve resources during stress.

Unlike auxins, cytokinins, and gibberellins, which promote growth, ABA serves as a growth suppressant, particularly under environmental stress conditions.

Conclusion: Abscisic acid is the primary hormone that inhibits plant growth, particularly during stress.

Acetylcholinesterase is the enzyme that hydrolyzes acetylcholine in the synaptic cleft. This reaction breaks acetylcholine into acetate and choline, effectively terminating the nerve signal. Efficient acetylcholine breakdown ensures the post-synaptic neuron is not overstimulated.

Significance in Neural Function:

- Prevents continuous activation of the post-synaptic neuron.

- Maintains precision in synaptic signaling.

- Facilitates muscle relaxation after contraction.

Conclusion: Acetylcholinesterase is critical for regulating synaptic transmission by clearing acetylcholine from the synaptic cleft.

Kwashiorkor is caused by a severe deficiency of protein in the diet. It primarily affects children who consume enough calories but lack adequate protein intake. Symptoms include:

- Edema: Caused by reduced plasma proteins that disrupt fluid balance.

- Fatty liver: Resulting from impaired lipid transport.

- Growth retardation: Due to insufficient amino acids for cellular functions.

- Skin and hair changes: Including discoloration and flakiness.

Kwashiorkor is distinct from marasmus, which is caused by overall calorie deficiency.

Conclusion: Protein deficiency leads to kwashiorkor, characterized by edema, poor growth, and liver abnormalities.

The Islets of Langerhans in the pancreas consist of different types of cells that produce hormones involved in glucose regulation:

- Beta cells produce insulin, which lowers blood glucose levels.

- Alpha cells produce glucagon, which increases blood glucose levels.

- Delta cells produce somatostatin, which regulates the secretion of both insulin and glucagon.

Adrenaline, however, is not produced by the pancreas. It is synthesized by the adrenal medulla and is involved in the "fight or flight" response, increasing heart rate and blood glucose levels.

Conclusion: Adrenaline is not produced by the Islets of Langerhans; it is secreted by the adrenal glands.

Bromelain is a mixture of proteolytic enzymes extracted from the stem and fruit of pineapples. It is primarily used for breaking down proteins into peptides and amino acids. Bromelain's applications include:

- Aiding in protein digestion by breaking down dietary proteins in the stomach.

- Tenderizing meat by degrading muscle fibers, making the meat softer.

- Anti-inflammatory properties, which help reduce swelling and pain in conditions such as arthritis.

Conclusion: Bromelain is an enzyme that facilitates protein digestion and has additional applications in medicine and food processing.

Cellular respiration involves the breakdown of glucose to generate energy in the form of ATP. The primary processes involved are:

- Glycolysis: Breakdown of glucose into pyruvate, generating ATP and NADH.

- Krebs Cycle (Citric Acid Cycle): Further breakdown of pyruvate to produce ATP, NADH, and FADH2, with carbon dioxide as a byproduct.

- Electron Transport Chain: Utilizes NADH and FADH2 to drive ATP synthesis through oxidative phosphorylation.

The Calvin Cycle, in contrast, is a part of photosynthesis and involves the fixation of carbon dioxide into glucose in plants. It does not occur in cellular respiration.

Conclusion: The Calvin Cycle is not part of cellular respiration, as it is associated with photosynthesis.

The DNA molecule in a single human cell measures approximately 2 meters when fully extended. To fit inside the nucleus, which is only about 6 micrometers in diameter, the DNA undergoes an intricate packaging process:

1. The DNA is tightly wound around histone proteins to form nucleosomes.

2. These nucleosomes coil into chromatin fibers.

3. The chromatin is further folded and looped to form chromosomes during cell division.

This highly organized structure ensures efficient storage of genetic material while allowing accessibility for replication and transcription processes.

Conclusion: Despite its significant length, DNA is compactly folded to fit within the nucleus of a cell.

Diabetes Insipidus (DI) is a condition that disrupts the body's ability to regulate water balance, resulting in excessive thirst and the production of large volumes of dilute urine. Unlike Diabetes Mellitus, where glucose is present in the urine, DI involves no glucose in the urine. The primary causes include:

- Central DI: Insufficient secretion of antidiuretic hormone (ADH) by the hypothalamus or pituitary gland.

- Nephrogenic DI: A reduced ability of the kidneys to respond to ADH.

Symptoms include dehydration, frequent urination, and extreme thirst, which can lead to complications if not managed promptly.

Conclusion: Diabetes Insipidus is marked by excessive water loss in urine, absence of glucose in the urine, and significant dehydration.

The pH of a buffer solution can be calculated using the Henderson-Hasselbalch equation:

pH = pKa + log ([A⁻] / [HA])

Here, [A⁻] is the concentration of the conjugate base, and [HA] is the concentration of the acid.

If the ratio ([A⁻] / [HA]) is increased by 100 times, the change in pH (ΔpH) is calculated as:

ΔpH = log(100)

Since log(100) = 2, the pH of the buffer increases by 2 units.

Conclusion: A 100-fold increase in the base-to-acid ratio leads to an increase of 2 units in the pH of the acidic buffer.

Polystyrene is a thermoplastic polymer, meaning it softens when heated and hardens upon cooling. This property allows it to be remelted and reshaped multiple times, making it suitable for various applications like packaging materials, disposable cups, and insulation products.

In contrast, materials like Bakelite are thermosetting polymers. Thermosets undergo irreversible chemical changes during curing and cannot be remelted or reshaped. Nylon 6,6 is a type of synthetic fiber and is not categorized as a thermoplastic.

Conclusion: Polystyrene is a thermoplastic, characterized by its ability to be melted and reshaped repeatedly without undergoing irreversible changes.