Monosomy

Definition

Monosomy is a genetic condition characterized by the absence of one chromosome from a pair, leading to a total of 45 chromosomes instead of the usual 46. This condition can result in various developmental disorders and is often linked to significant health issues due to the loss of genetic information. Monosomy can affect any chromosome, but certain types, like Turner syndrome (monosomy X), are more common and well-studied.

5 Must Know Facts For Your Next Test

1. Monosomy typically results from errors during meiosis, specifically nondisjunction, when chromosomes fail to separate properly.
2. The most recognized form of monosomy is Turner syndrome, which affects females and is characterized by short stature and reproductive issues.
3. Monosomy can lead to severe developmental delays, congenital abnormalities, and increased risk for certain medical conditions depending on which chromosome is affected.
4. Many monosomic embryos do not survive to term, which contributes to the relatively low prevalence of this genetic condition in live births.
5. Detection of monosomy often involves karyotyping, a laboratory technique used to visualize chromosomes and identify any abnormalities.

Review Questions

• How does monosomy occur and what are some common consequences associated with this chromosomal condition?
  • Monosomy occurs due to nondisjunction during meiosis, where homologous chromosomes fail to separate, resulting in gametes with missing chromosomes. When such gametes contribute to fertilization, the resulting zygote will have one less chromosome than normal. The consequences of monosomy can vary significantly based on which chromosome is affected, but they often include developmental delays, physical anomalies, and increased susceptibility to certain health conditions.
• Compare and contrast monosomy with trisomy and explain the implications of each on human development.
  • Monosomy involves the absence of one chromosome from a pair, while trisomy involves an extra chromosome. Both conditions fall under the umbrella of aneuploidy and can lead to significant developmental issues. For instance, while Turner syndrome (monosomy X) affects females with a range of health problems like infertility and heart defects, Down syndrome (trisomy 21) can result in intellectual disability and distinct physical characteristics. Each condition disrupts normal development in unique ways based on the specific genes involved.
• Evaluate the potential impacts of diagnosing monosomy early in pregnancy through prenatal testing techniques.
  • Early diagnosis of monosomy through prenatal testing such as amniocentesis or chorionic villus sampling allows for informed decision-making regarding pregnancy management. If monosomy is detected, parents may choose to prepare for potential medical interventions or consider their options regarding the continuation of the pregnancy. Additionally, early diagnosis provides healthcare professionals the opportunity to monitor and address potential health issues that could arise as the pregnancy progresses, ultimately impacting neonatal care and support.

Related terms

aneuploidy:

Aneuploidy refers to an abnormal number of chromosomes in a cell, which includes both monosomy (missing one chromosome) and trisomy (an extra chromosome).

chromosomal deletion: Chromosomal deletion is a mutation where a portion of the chromosome is missing, which can also lead to genetic disorders, similar to monosomy.

Turner syndrome:

Turner syndrome is a specific condition resulting from the monosomy of the X chromosome, causing various developmental and physical issues in females.