Question

a gene can be defined as which of the following? a specific chemical found in the nucleus of a cell that governs all aspects of its structure and function a foreign protein that causes the immune system to create an antibody an identifiable portion of a strand of dna that contains the instructions for a single structure or function a small, nontoxic amount of a foreign substance

Explanation:

To determine the correct definition of a gene, we analyze each option:

• Option 1: A chemical governing cell structure/function is not a gene (genes are DNA/RNA segments).
• Option 2: A foreign protein causing antibody production is an antigen, not a gene.
• Option 3: A gene is a segment of DNA (or RNA in some cases) that holds the instructions for making a specific protein or performing a function, matching "an identifiable portion of a strand of DNA that contains the instructions for a single structure or function".
• Option 4: A small foreign substance is a vaccine - like component, not a gene.

Answer:

an identifiable portion of a strand of DNA that contains the instructions for a single structure or function (the option with this description)