T cells are first positively selected in the thymus by binding to an HLA molecule.

Humans normally have 22 pairs of autosomes and 2 pairs of sex chromosomes.

Which of the following statements best describes genes?

The enzyme reverse transcriptase possessed by HIV catalyzes the conversion of which of the following?

Which of the following statements about tumors is correct?

Mediators of inflammation are biologically active compounds derived from the cells or blood plasma.

What does the ending -itis indicate when it is affixed to the name of an organ or tissue (e.g., hepatitis)?

A mother has given birth to an infant with cytomegalic inclusion disease. What does this indicate?

Which of the following refers to the absence of a chromosome?

A middle-aged man has a communicable disease caused by a virus that is excreted in the feces. Which of the following measures could be least effective or ineffective in limiting the spread of the infection?