How many chromosomes are present in a normal human gamete (sperm or egg)?
B. 23
Gametes are haploid (n = 23); body cells are diploid (2n = 46).
Which blood vessel carries oxygenated blood from the lungs to the heart?
D. Pulmonary vein
The pulmonary vein is the exception: a vein carrying oxygenated blood to the left atrium.
What is the structural and functional unit of the kidney?
C. Nephron
Each kidney contains about a million nephrons that filter blood.
Which enzyme unwinds the DNA double helix at the replication fork?
B. Helicase
Helicase breaks hydrogen bonds between the base pairs to separate the strands.
Which cell organelle is the site of protein synthesis?
A. Ribosome
Ribosomes translate mRNA into polypeptides.