Definition

Noun: A type of chromosomal abnormality characterized by the presence of only one copy of a particular chromosome in the cells, instead of the normal two copies (diploid number). This results from the failure of chromosome pairs to separate properly during cell division.

Usage

The term is used specifically in the fields of genetics, cytogenetics, and medicine to describe a specific genetic condition. * Turner syndrome is a well-known example of a monosomy, where a female is born with only one X chromosome (45,X). * The genetic test revealed a monosomy of chromosome 21 in the sampled cells. * Monosomy for most autosomes is not compatible with life and often leads to early miscarriage.

Advanced Usage

• "Partial monosomy": Refers to a condition where only a segment of a chromosome is missing, rather than the entire chromosome. This is also known as a deletion.
  • Cri-du-chat syndrome is caused by a partial monosomy of the short arm of chromosome 5.

Variants and Related Words

• Aneuploidy (n): The general category of chromosomal abnormalities involving an abnormal number of chromosomes, which includes both monosomy and trisomy.
• Trisomy (n): The opposite condition, characterized by having three copies of a particular chromosome instead of two (e.g., Down syndrome, Trisomy 21).
• Nondisjunction (n): The failure of chromosome pairs to separate correctly during cell division (meiosis or mitosis), which is the primary cause of monosomy and trisomy.

Synonyms

• Chromosomal deletion (when referring to a partial loss)
• Chromosome loss

Antonyms

• Disomy (the normal state of having two copies)
• Trisomy (having three copies)

Noun

1. chromosomal abnormality consisting of the absence of one chromosome from the normal diploid number