What is a karyotype?

A karyotype is defined as a picture of all the chromosomes in a cell arranged in pairs. This method involves staining the chromosomes to make them visible under a microscope, allowing scientists to examine their number and structure. Karyotyping is essential in genetics for identifying chromosomal abnormalities, such as those found in genetic disorders and cancers. For instance, a karyotype can reveal whether an individual has the normal number of chromosomes, which is 46 in humans, or if there are any extra or missing chromosomes, such as in Down syndrome where there is an extra copy of chromosome 21.

In contrast, other options describe different concepts. A diagram of phenotypes represents the observable traits of an organism, which is not the same as karyotyping. A record of organism behavior pertains to ethology or behavioral studies, while a study of gene expression focuses on how genes are turned on or off in different cells or environments, which does not involve the organization of chromosomes.