What is the definition of monosomy in genetics?

Monosomy in genetics refers to a condition in which an individual is missing one chromosome from a typical pair. In humans, for instance, individuals typically have 23 pairs of chromosomes, totaling 46. When one chromosome from a pair is absent, it results in monosomy. This can lead to various genetic disorders or developmental issues depending on which chromosome is missing.

The remaining options describe different genetic concepts. For example, having an extra chromosome corresponds to trisomy, not monosomy. A genetic mutation typically refers to a change or alteration in the DNA sequence, which is a broader concept and does not specifically relate to chromosome number. Lastly, the presence of one dominant allele and one recessive allele pertains to genetic expression and inheritance patterns rather than chromosomal count or configuration. Thus, the correct definition focuses specifically on the absence of one chromosome, which is the essence of the term monosomy.