What is a chromosomal abnormality?

A chromosomal abnormality refers to a situation where an individual has an atypical number of chromosomes, which can manifest as either having too many or too few chromosomes. This is significant because chromosomes contain our genetic material, and any alterations in their number can lead to various developmental and health issues. For example, Down syndrome is caused by an extra copy of chromosome 21, resulting in a total of 47 chromosomes instead of the typical 46.

In contrast, having the correct number of chromosomes or a completely normal genetic makeup does not represent a chromosomal abnormality; these conditions indicate typical chromosomal configuration, which is considered normal. The mention of dominant genes is also irrelevant because chromosomal abnormalities can affect genes regardless of whether they are dominant or recessive. Thus, inheriting an incorrect number of chromosomes correctly defines what a chromosomal abnormality is.