Which genetic disorder is caused by the presence of an additional copy of chromosome 21?
Solution
Correct Answer: Option B
The genetic disorder caused by the presence of an additional copy of chromosome 21 is Down syndrome. This condition is also known as trisomy 21 because individuals with this syndrome have three copies of chromosome 21 instead of the usual two. The extra genetic material affects normal development, leading to characteristic physical features, intellectual disability, and an increased risk of certain medical conditions such as congenital heart defects and respiratory problems.
To clarify the other options:
- Klinefelter syndrome (Option 1) is caused by the presence of an extra X chromosome in males (47,XXY).
- Turner syndrome (Option 3) results from a missing X chromosome in females (45,X).
- Edwards syndrome (Option 4), or trisomy 18, is caused by an additional copy of chromosome 18, leading to severe developmental and health issues.
Therefore, the correct answer is Down syndrome, highlighting the role of chromosome 21 trisomy in this disorder.
Reference: Robbins Basic Pathology, 10th Edition, Chapter 7: Genetic Disorders
To clarify the other options:
- Klinefelter syndrome (Option 1) is caused by the presence of an extra X chromosome in males (47,XXY).
- Turner syndrome (Option 3) results from a missing X chromosome in females (45,X).
- Edwards syndrome (Option 4), or trisomy 18, is caused by an additional copy of chromosome 18, leading to severe developmental and health issues.
Therefore, the correct answer is Down syndrome, highlighting the role of chromosome 21 trisomy in this disorder.
Reference: Robbins Basic Pathology, 10th Edition, Chapter 7: Genetic Disorders
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