Aneuploidy

Definition

Aneuploidy is a genetic condition characterized by an abnormal number of chromosomes in a cell, which can lead to various developmental and health issues. It often arises during cell division, particularly meiosis, when the chromosomes fail to separate properly, leading to gametes with too few or too many chromosomes. This condition can result in congenital disorders and birth defects when it affects the zygote after fertilization.

5 Must Know Facts For Your Next Test

1. Aneuploidy occurs in approximately 10-25% of all human pregnancies, with many cases leading to miscarriage.
2. Common forms of aneuploidy include trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome), and monosomy X (Turner syndrome).
3. The risk of aneuploidy increases with maternal age, particularly for women over 35, due to age-related factors affecting meiotic cell division.
4. Aneuploidy can result in a range of congenital disorders, characterized by physical, developmental, and intellectual challenges.
5. Detection methods for aneuploidy include prenatal screening techniques such as chorionic villus sampling (CVS) and amniocentesis.

Review Questions

• How does nondisjunction during meiosis contribute to the occurrence of aneuploidy?
  • Nondisjunction occurs when homologous chromosomes or sister chromatids fail to separate properly during meiosis. This failure can lead to gametes that contain either an extra chromosome or a missing chromosome. When these gametes fuse during fertilization, the resulting zygote will have an abnormal number of chromosomes, resulting in aneuploidy. This mechanism is a primary cause of various genetic disorders.
• Discuss how maternal age influences the risk of aneuploidy and its implications for prenatal care.
  • Maternal age is a significant risk factor for aneuploidy, particularly for women over 35 years old. As women age, their eggs are more likely to experience nondisjunction during meiosis, increasing the likelihood of chromosomal abnormalities like Down syndrome. Prenatal care for older mothers often includes enhanced screening methods to detect aneuploidy early in pregnancy, allowing for informed decision-making regarding potential interventions and planning for any congenital disorders that may arise.
• Evaluate the impact of aneuploidy on human development and health, citing specific examples.
  • Aneuploidy has a profound impact on human development and health, often resulting in congenital disorders with varying degrees of severity. For example, trisomy 21 leads to Down syndrome, characterized by intellectual disability and distinct physical features. Similarly, Turner syndrome results from monosomy X and can cause short stature and reproductive issues. The presence of these chromosomal abnormalities illustrates how aneuploidy disrupts normal development and contributes to a spectrum of health challenges that require ongoing medical support.

Related terms

Nondisjunction: Nondisjunction is the failure of homologous chromosomes or sister chromatids to separate properly during cell division, resulting in aneuploidy.

Trisomy: Trisomy is a specific type of aneuploidy where there are three copies of a particular chromosome instead of the normal two, such as in Down syndrome (trisomy 21).

Karyotype: A karyotype is a visual representation of an individual's chromosomes, which can be used to identify aneuploidy and other chromosomal abnormalities.