Chromosomal non-disjunction responsible for all except
**Core Concept**
Chromosomal non-disjunction is a process where pairs of chromosomes fail to separate properly during cell division, leading to an abnormal number of chromosomes in the resulting cells. This can result in various genetic disorders, including Down syndrome, Turner syndrome, and Klinefelter syndrome.
**Why the Correct Answer is Right**
Chromosomal non-disjunction occurs due to errors in meiosis or mitosis, leading to aneuploidy, where cells have an abnormal number of chromosomes. This can result in various genetic disorders, including Down syndrome (trisomy 21), which is caused by an extra copy of chromosome 21. Turner syndrome (45,X) and Klinefelter syndrome (47,XXY) are also caused by chromosomal non-disjunction.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because chromosomal non-disjunction does not cause cystic fibrosis, which is a genetic disorder caused by a mutation in the CFTR gene, not an abnormal number of chromosomes.
**Option B:** This option is incorrect because chromosomal non-disjunction does not cause sickle cell anemia, which is a genetic disorder caused by a mutation in the HBB gene, not an abnormal number of chromosomes.
**Option C:** This option is incorrect because chromosomal non-disjunction does not cause Tay-Sachs disease, which is a genetic disorder caused by a mutation in the HEXA gene, not an abnormal number of chromosomes.
**Clinical Pearl / High-Yield Fact**
Chromosomal non-disjunction is a common cause of genetic disorders, and it can occur in any chromosome, but it's more frequent in certain chromosomes, such as chromosomes 21, 18, and 13.
**Correct Answer: D. All the above**