What is the genome?

• A. The complete instructions for making an organism, consisting of all the genetic material in that organism's chromosomes.
• B. A single gene copied many times.
• C. The protein machinery within mitochondria.
• D. The set of body plan diagrams used in embryology.

Answer: (A)

The genome is the complete set of genetic material that contains all the instructions for building and operating an organism. This includes all genes and the noncoding sequences that regulate them, and in many cases the DNA housed in chromosomes (with some definitions also encompassing genetic material in organelles like mitochondria). That full collection of genetic information is what the genome represents, so the option describing the complete instructions encoded in all the genetic material within chromosomes fits this idea best.

The other ideas aren’t the genome: a single gene copied many times is just one gene or a gene family, not the full set of genetic material. The protein machinery within mitochondria is part of the cell’s function, not the genome itself. And a set of embryology diagrams is a teaching resource, not genetic material.