What term describes the addition or subtraction of one chromosome from the diploid genome?

The term that describes the addition or subtraction of one chromosome from the diploid genome is "aneuploid." This condition occurs when an organism has either more or fewer chromosomes than the typical diploid number, resulting in an abnormal chromosome count. For instance, if a human has 47 chromosomes instead of the usual 46, this would be categorized as an aneuploid condition, which is often associated with various genetic disorders, such as Down syndrome, which is caused by the presence of an extra copy of chromosome 21.

Gene expression refers to the process through which information from a gene is used to synthesize functional gene products, typically proteins, and does not pertain to the number of chromosomes in a genome. Translocation involves the rearrangement of chromosomes, specifically when a segment of one chromosome breaks off and attaches to another chromosome, which is different from the simple addition or subtraction of entire chromosomes. Deletion involves the loss of a portion of a chromosome, which may affect genetic material, but it does not describe the overall aneuploid condition itself.