Molecular Biology & Recombinant DNA methods

• Dental Morphological Classifications:
• Brachyodont Teeth (Short-crowned): Low crown, distinct neck at the gumline, and well-developed roots with closed apical foramina. Found in carnivores (Dog, Cat) and omnivores/humans.
• Hypsodont Teeth (High-crowned): Exceptionally high crown with root formation delayed until late in life. The tooth continues to erupt throughout adult life to compensate for continual mechanical attrition from masticating abrasive silicates in forage:
• Characteristic of the Horse (all equine cheek teeth and incisors) and domestic ruminants.
• nalysis:
• (Horse): Correct species possessing hypsodont dentition.

Correct option: (3) Horse

• Protease Inhibitor Families:
• Cysteine Proteases: Enzymes (e.g., papain, ficin, lysosomal cathepsins B, H, K, L) that utilize a catalytic cysteine thiol ($-SH$) nucleophile.
• Cystatin C (and the Cystatin Superfamily):
• Specific, physiological, high-affinity reversible protein inhibitors of cysteine proteases.
• Widely expressed across tissues and body fluids, regulating intracellular catabolism and preventing inappropriate extracellular tissue degradation.
• (EDTA inhibits metalloproteases by chelating divalent cations; PMSF specifically inhibits serine proteases).
• nalysis:
• (Cystatin C): Correct cysteine protease inhibitor.

Correct option: (3) Cystatin C

• Evaluation of Statements:
• Assertion (A): The increase in concentration of substrate can alleviate inhibition of competitive enzymes.
• True. Competitive inhibitors bind reversibly to the active catalytic site in direct competition with substrate. Elevating substrate concentration ($[S] \gg [I]$) displaces the inhibitor, restoring the maximum reaction velocity ($V_{max}$).
• Reason (R): Allosteric proteins have similar regulatory and substrate binding functional sites.
• False. By fundamental definition, allosteric enzymes possess spatially distinct and non-identical sites: a catalytic site for the substrate and separate, physically remote allosteric sites for regulatory modulators.
• nalysis:
• ((A) is correct but (R) is not correct): Correct.

• Quaternary Structure of Lactate Dehydrogenase (LDH):
• LDH is a tetrameric enzyme composed of two distinct polypeptide subunits: $M$ (Muscle) and $H$ (Heart), assembling into five distinct isozymes:

• LDH-1 ($H_4$ / $HHHH$): Heart muscle and erythrocytes ($\gt 90\%$ of cardiac LDH).
• LDH-2 ($H_3M$): Reticuloendothelial system and heart.
• LDH-3 ($H_2M_2$): Lungs and spleen.
• LDH-4 ($HM_3$): Kidneys and pancreas.
• LDH-5 ($M_4$ / $MMMM$): Skeletal muscle and liver.
  • nalysis:

• (HHHH): Correct cardiac LDH isozyme.