COMLEX-USA Biomedical Sciences

Question 1

Which enzyme is deficient in Tay-Sachs disease, leading to accumulation of GM2 ganglioside?

Accepted Answer

Hexosaminidase A

Answer

Tay-Sachs disease results from deficiency of hexosaminidase A, causing GM2 ganglioside accumulation in lysosomes.

Question 2

A mutation in which gene is most commonly associated with hereditary breast and ovarian cancer syndrome?

Accepted Answer

BRCA1/2

Answer

BRCA1 and BRCA2 mutations are the most common inherited cause of breast and ovarian cancer syndrome.

Question 3

The 'watershed' area between the superior and inferior mesenteric artery territories, most vulnerable to ischemia, is located at:

Accepted Answer

Splenic flexure

Answer

The splenic flexure of the colon is a watershed zone between SMA and IMA territories and is most vulnerable to ischemic colitis.

Question 4

Which complement pathway is activated by antibody-antigen complexes and begins with C1q binding?

Accepted Answer

Classical pathway

Answer

The classical complement pathway is activated when C1q binds to antibody-antigen complexes, initiating the complement cascade.

Question 5

During which phase of the cell cycle does DNA replication occur?

Accepted Answer

S phase

Answer

DNA synthesis and replication occur during S (synthesis) phase of the cell cycle.

COMLEX-USA Practice Test