OAT Biology 3

Question 1

Which layer of the skin contains melanocytes?

Accepted Answer

Stratum basale

Answer

Melanocytes reside in the stratum basale (deepest epidermal layer) and produce melanin pigment.

Question 2

The Calvin cycle (light-independent reactions) occurs in which part of the chloroplast?

Accepted Answer

Stroma

Answer

Carbon fixation via the Calvin cycle takes place in the stroma, where RuBisCO converts CO₂ into G3P.

Question 3

Which immunoglobulin class is the FIRST to be produced in a primary immune response?

Accepted Answer

IgM

Answer

IgM is the first antibody produced during a primary immune response before class switching occurs.

Question 4

The enzyme that unwinds the double helix ahead of the replication fork is called:

Accepted Answer

Helicase

Answer

Helicase breaks hydrogen bonds between base pairs to unwind the DNA double helix at the replication fork.

Question 5

Which of the following is an example of negative feedback in the endocrine system?

Accepted Answer

Progesterone inhibiting FSH and LH secretion

Answer

Progesterone's inhibition of FSH and LH is classic negative feedback, dampening the hormone signal that caused its release.

OAT - Optometry Admission Test Practice Test