Monosomy

Definition

Monosomy is a type of chromosomal abnormality where there is a missing chromosome from a pair, resulting in a diploid organism having only one copy of a particular chromosome instead of the usual two. This condition can lead to various developmental issues and is often associated with specific syndromes. Monosomy is significant because it can arise during cell division processes like meiosis or mitosis, affecting the genetic makeup of the resulting cells.

5 Must Know Facts For Your Next Test

1. Monosomy most commonly affects the X chromosome, leading to Turner Syndrome in females, which can result in developmental and reproductive issues.
2. It typically arises from errors during meiosis, specifically non-disjunction, where chromosomes fail to separate properly during cell division.
3. Cells with monosomy often exhibit phenotypic abnormalities due to the loss of essential genes located on the missing chromosome.
4. Monosomic conditions are generally more severe than those with an extra chromosome (trisomy) because losing a chromosome means losing multiple genes.
5. Individuals with monosomy can have varied survival outcomes; while some conditions may be incompatible with life, others may allow for normal or near-normal development.

Review Questions

• How does monosomy occur during meiosis, and what are the implications for genetic variation?
  • Monosomy occurs when there is a failure in chromosome segregation during meiosis, specifically through a process called non-disjunction. As a result, one gamete receives no copy of a chromosome while another receives two. When these gametes combine during fertilization, the resulting zygote has only one copy of that chromosome, leading to monosomy. This lack of genetic variation can have serious consequences for the organism's development and health.
• Discuss how Turner Syndrome exemplifies the clinical consequences of monosomy and its effect on individuals.
  • Turner Syndrome is a direct example of monosomy, specifically involving the loss of one X chromosome in females. This condition results in various physical and developmental challenges, including short stature, infertility, and heart defects. The absence of genetic material impacts multiple body systems, showcasing how monosomy can lead to significant clinical manifestations. Management often involves hormone therapies and supportive care to address growth and reproductive challenges.
• Evaluate the broader implications of monosomy on human health and genetic counseling practices.
  • Monosomy presents unique challenges for human health as it can lead to serious genetic disorders that significantly affect quality of life. For genetic counseling practices, understanding monosomy helps inform risk assessments for prospective parents, especially those with known chromosomal abnormalities in their family histories. It also aids in explaining potential outcomes for pregnancies diagnosed with monosomic conditions through prenatal testing. By providing accurate information about risks and management options, genetic counselors play a crucial role in supporting affected individuals and families.

Related terms

Aneuploidy: A condition involving an abnormal number of chromosomes in a cell, which can include both monosomy and trisomy.

Turner Syndrome:

A chromosomal disorder that occurs when a female is partly or completely missing an X chromosome, resulting in monosomy X (45,X).

Meiosis: A specialized type of cell division that reduces the chromosome number by half, leading to the formation of gametes; errors during meiosis can lead to conditions like monosomy.