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 challenges. This condition is also known as Trisomy 21 and is one of the most common chromosomal abnormalities found in humans, impacting physical growth, cognitive ability, and overall health.

5 Must Know Facts For Your Next Test

1. Down syndrome occurs in approximately 1 in 700 births, making it one of the most common genetic disorders.
2. Individuals with Down syndrome often exhibit distinct physical features, such as a flat facial profile, slanted eyes, and a single transverse palmar crease.
3. While there is no cure for Down syndrome, early intervention programs can help improve quality of life and developmental outcomes for affected individuals.
4. Individuals with Down syndrome may experience various health issues, including heart defects, gastrointestinal problems, and increased risk for certain medical conditions.
5. The likelihood of having a child with Down syndrome increases with maternal age, particularly for women over 35 years old.

Review Questions

• How does the chromosomal abnormality in Down syndrome lead to its characteristic features?
  • Down syndrome is primarily caused by the presence of an extra chromosome 21 due to nondisjunction during cell division. This additional genetic material alters normal development processes, leading to the physical features and intellectual challenges associated with the condition. The specific genes located on chromosome 21 are believed to influence growth and cognitive function, resulting in the unique phenotype observed in individuals with Down syndrome.
• Evaluate the role of early intervention programs in improving outcomes for individuals with Down syndrome.
  • Early intervention programs play a crucial role in improving developmental outcomes for individuals with Down syndrome by providing specialized therapies and educational support from a young age. These programs focus on enhancing speech and language skills, motor skills, and social interactions, which can significantly improve cognitive abilities and quality of life. Research shows that children who receive early intervention are more likely to achieve better educational results and greater independence as they grow older.
• Analyze how maternal age influences the risk of having a child with Down syndrome and discuss the implications for genetic counseling.
  • Maternal age is a significant factor influencing the risk of having a child with Down syndrome, as older women have a higher chance of experiencing nondisjunction during egg formation. For instance, women over 35 years old are at a greater risk compared to younger mothers. This correlation underscores the importance of genetic counseling for expectant parents, particularly those in higher risk categories. Counselors can provide information about screening options, potential outcomes, and resources to support families affected by Down syndrome.

Related terms

Chromosome: A structure made of DNA and protein that contains genetic information; humans typically have 46 chromosomes arranged in 23 pairs.

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

Phenotype: The observable physical and biochemical characteristics of an organism, determined by both genetic makeup and environmental influences.