Question 31

Down syndrome is a disorder that results from carrying extra genetic material from chromosome 21.

Down syndrome occurs when an individual has an extra copy of chromosome 21, leading to various physical and intellectual disabilities. This genetic anomaly is the defining characteristic of Down syndrome.

A) A disorder in which red blood cells are irregularly shaped, die early, and leave a shortage of healthy red blood cells

This option describes sickle cell anemia, a completely different disorder related to blood cell shape and function. It does not pertain to genetic conditions or chromosomal abnormalities, which are the focus of Down syndrome.

B) A disorder that occurs due to prenatal exposure to alcohol

This option refers to fetal alcohol spectrum disorders (FASD), which arise from alcohol exposure during pregnancy. While these disorders affect development, they do not relate to chromosomal abnormalities like Down syndrome.

C) A disorder caused by folate or Vitamin B9 deficiency during fetal development

This option relates to neural tube defects, which can occur due to a lack of folate during pregnancy. However, this does not involve chromosomal issues or the extra genetic material characteristic of Down syndrome.

D) A disorder that results from carrying extra genetic material from chromosome 21

This option accurately describes Down syndrome, which is recognized as trisomy 21, where an individual has three copies of chromosome 21 instead of the usual two. This additional genetic material leads to the developmental and physical features associated with the condition.

Conclusion

The correct answer, D, clearly identifies Down syndrome as a genetic disorder resulting from an extra chromosome 21. All other options describe different medical conditions that do not involve the genetic aspect of Down syndrome, highlighting the importance of understanding chromosomal abnormalities in genetic disorders.