OAT General Biology 4

Question 1

In an experiment, a gene is expressed in muscle tissue but silenced in nerve tissue. This best illustrates:

Accepted Answer

Differential gene expression

Answer

Differential gene expression occurs when the same genome produces different proteins in different cell types based on which genes are active.

Question 2

Which component of the immune system produces antibodies?

Accepted Answer

B plasma cells

Answer

B cells differentiate into plasma cells upon antigen activation, and plasma cells are the antibody-secreting effector cells of humoral immunity.

Question 3

The primary function of the loop of Henle in the kidney is to:

Accepted Answer

Create a concentration gradient in the medulla

Answer

The loop of Henle establishes a hyperosmotic gradient in the renal medulla through countercurrent multiplication, which drives water reabsorption from the collecting duct.

Question 4

Which of the following best describes a sympatric speciation event?

Accepted Answer

New species arise within the same geographic area

Answer

Sympatric speciation occurs without geographic isolation, often through polyploidy, sexual selection, or ecological divergence within the same habitat.

Question 5

Which nitrogenous base is found in RNA but NOT in DNA?

Accepted Answer

Uracil

Answer

RNA contains uracil (U) instead of thymine (T), and uracil pairs with adenine just as thymine does in DNA.

OAT - Optometry Admission Test Practice Test

OAT - Optometry Admission Test Practice Test

OAT General Biology 4