Down syndrome

Definition

Down syndrome is a genetic disorder caused by the presence of an extra copy of chromosome 21, leading to developmental and physical challenges. This condition is characterized by a distinct set of features, including intellectual disability, unique facial characteristics, and an increased risk for certain medical conditions. Understanding Down syndrome provides insights into chromosomal abnormalities and how variations in genetic material can affect human development.

5 Must Know Facts For Your Next Test

1. Down syndrome occurs in approximately 1 in 700 births and affects individuals regardless of race or socioeconomic status.
2. There are three types of Down syndrome: Trisomy 21 (the most common), Translocation Down syndrome, and Mosaic Down syndrome.
3. Individuals with Down syndrome often exhibit hypotonia (reduced muscle tone) at birth, which can impact their physical development.
4. Early intervention programs focusing on speech, occupational, and physical therapy can significantly enhance the development and quality of life for individuals with Down syndrome.
5. People with Down syndrome have an increased risk of developing certain health issues, such as congenital heart defects, respiratory problems, and thyroid conditions.

Review Questions

• How does the presence of an extra chromosome contribute to the characteristics observed in individuals with Down syndrome?
  • The presence of an extra copy of chromosome 21, known as Trisomy 21, leads to a range of developmental and physical characteristics associated with Down syndrome. This additional genetic material disrupts normal development processes, resulting in intellectual disabilities and specific facial features like a flat facial profile and slanted eyes. The extra chromosome also influences various organ systems, increasing the likelihood of certain health issues.
• What are the implications of nondisjunction in the context of Down syndrome, and how does it differ from other chromosomal disorders?
  • Nondisjunction is a key process that results in Down syndrome when it occurs during meiosis, leading to gametes with an abnormal number of chromosomes. In the case of Down syndrome, this results in fertilization with a gamete that carries an extra chromosome 21. This differs from other chromosomal disorders where nondisjunction might involve different chromosomes or result in other types of abnormalities like deletions or duplications. Understanding nondisjunction helps in identifying potential risk factors for Down syndrome in future pregnancies.
• Evaluate the role of early intervention strategies in improving outcomes for individuals with Down syndrome and their families.
  • Early intervention strategies play a crucial role in enhancing the developmental trajectory for individuals with Down syndrome. Programs that focus on speech therapy, physical therapy, and occupational therapy have shown significant positive impacts on communication skills and daily functioning. These interventions not only benefit the individual but also support families by providing them with resources and knowledge about managing developmental challenges. As a result, early intervention contributes to better quality of life and independence for individuals with Down syndrome as they grow.

Related terms

Trisomy 21: A type of chromosomal abnormality where there are three copies of chromosome 21 instead of the usual two, which is the primary cause of Down syndrome.

Karyotype: A visual representation of an individual's chromosomes, used to identify chromosomal abnormalities such as those seen in Down syndrome.

Nondisjunction: The failure of homologous chromosomes or sister chromatids to separate properly during cell division, which can lead to conditions like Down syndrome.