How is monosomy characterized in chromosome count?

Monosomy is characterized by the loss of a single chromosome from the normal diploid set. In humans, this means that instead of having two copies of a particular chromosome, the individual has only one copy. This results in a total chromosome count that is one less than the typical diploid number. For example, in humans, the normal diploid chromosome count is 46, so monosomy would result in a count of 45 chromosomes. The condition can lead to various developmental and health issues, as having only one copy of a chromosome can disrupt gene dosage and expression.

Other choices describe different chromosomal anomalies: gaining an additional chromosome would refer to trisomy, while having all chromosomes in triplicates describes tetrasomy, and having two extra chromosomes implies a state of polysomy. These conditions are distinctly different from monosomy, highlighting its specific definition in the context of chromosomal abnormalities.