Explanation

Humans have 22 pairs of autosomes and 1 pair of sex chromosomes.

Chromosome 21 is the smallest autosome in terms of base pairs.

Chromosome 1 is the largest autosome.

Chromosome 23 refers to sex chromosomes (X or Y), not autosomes.

Chromosome 21 is associated with Down syndrome when trisomic.

Last updated question 17-02-2026

Explanation

• The nephron is the functional unit of the kidney.
• Sodium reabsorption occurs at different parts of the nephron.
• Thick loop of Henle actively pumps out Na⁺ using ATP (active transport).
• Thin loop of Henle mainly allows passive movement of water and ions.
• Proximal tubule reabsorbs Na⁺ mainly by secondary active transport; collecting duct fine-tunes Na⁺ under hormonal control (aldosterone).

Last updated question 17-02-2026

Explanation

• T₃ (Triiodothyronine) and T₄ (Thyroxine) are thyroid hormones.
• They are produced in the thyroid gland.
• They are formed by iodination of the amino acid tyrosine.
• Iodinated tyrosine molecules (iodotyrosine) combine to form T₃ and T₄.
• Dopamine and GABA are neurotransmitters, not thyroid hormone precursors.

Last updated question 17-02-2026

Explanation

Active transport is a critical process in the nephron used to reabsorb solutes against their concentration gradients

Proximal Tubule:

This is the primary site of active transport, where approximately 65–70% of filtered sodium is reabsorbed via the Na⁺/K⁺-ATPase pump.

It also uses secondary active transport to reabsorb 100% of filtered glucose and amino acids.

Last updated question 17-02-2026

Explanation

•  Mammary glands are modified sweat glands.
•  They produce milk for offspring.
•  Structurally, they retain sweat gland features.
•  They are present in mammals only.
•  Hormones regulate their secretion.

Last updated question 17-02-2026