Down syndrome

Definition

Down syndrome is a genetic disorder caused by the presence of an extra copy of chromosome 21, which leads to developmental and intellectual delays. This condition results from errors in cell division during meiosis, specifically nondisjunction, where chromosomes fail to separate properly. The presence of this extra genetic material impacts physical growth, cognitive ability, and overall health.

5 Must Know Facts For Your Next Test

1. Down syndrome occurs in about 1 in 700 live births and is one of the most common chromosomal conditions.
2. Individuals with Down syndrome may exhibit distinct physical features such as a flat facial profile, slanted eyes, and a single transverse palmar crease.
3. The severity of developmental delays associated with Down syndrome varies widely among individuals; some may have mild disabilities while others may have more significant challenges.
4. Most cases of Down syndrome are not inherited but result from random errors during meiosis; however, maternal age can increase the risk of having a child with Down syndrome.
5. Regular medical check-ups and early intervention programs can significantly enhance the quality of life and development for individuals with Down syndrome.

Review Questions

• How does nondisjunction during meiosis lead to Down syndrome?
  • Nondisjunction occurs when homologous chromosomes fail to separate properly during meiosis, resulting in gametes that have an abnormal number of chromosomes. If one of these gametes contributes to the formation of an embryo, it can lead to an individual with an extra copy of chromosome 21, which is the genetic basis for Down syndrome. This extra chromosome affects the individual's development and can lead to various health challenges and physical traits associated with the condition.
• Discuss the implications of maternal age on the likelihood of having a child with Down syndrome.
  • Maternal age has been shown to significantly influence the risk of having a child with Down syndrome. As women age, especially those over 35 years old, there is an increased chance that nondisjunction will occur during egg formation, leading to higher instances of trisomy 21. This correlation highlights the importance of prenatal counseling and genetic testing options for older mothers considering pregnancy.
• Evaluate how understanding the genetic basis of Down syndrome can impact support and intervention strategies for affected individuals.
  • Understanding that Down syndrome is caused by an extra chromosome 21 provides valuable insights into potential developmental challenges and health issues faced by individuals. This knowledge allows healthcare professionals and educators to tailor support services effectively, ensuring that interventions address specific needs such as speech therapy, occupational therapy, and educational adaptations. By recognizing the unique profiles associated with Down syndrome, families and communities can foster inclusive environments that promote well-being and optimal development for those affected by this condition.

Related terms

Nondisjunction: A failure of homologous chromosomes or sister chromatids to separate properly during cell division, leading to an abnormal number of chromosomes in daughter cells.

Trisomy 21: Another term for Down syndrome, which refers specifically to the presence of three copies of chromosome 21 instead of the usual two.

Karyotype: A laboratory technique that allows for the visual representation of an individual's chromosomes, used to identify chromosomal abnormalities like those seen in Down syndrome.