Which disease is attributed to nondisjunction? a) hemophilia b) down's syndrome c) cystic fibrosis d) sickle-cell anemia

Down's syndrome

Explanation:

Down syndrome also called trisomy 21 is a chromosomal disorder (aneuploidy) in which an extra chromosome is added to chromosome 21 in humans. It is caused by a term called NONDISJUNCTION.

Meiotic nondisjunction is a phenomenon whereby pairs of homologous chromosomes or sister chromatids fail to separate during meiosis. Nondisjunction can occur during meiosis I or II.

Meiotic nondisjunction produces gametes with anomalies i.e. gametes with extra copies of chromosome (n+1) or deficient of chromosomes (n-1). Note that, a normal haploid gamete is (n). When this gametes with anomalies combine with normal gametes during fertilization, they produce a chromosomal disorder known as ANEUPLOIDY in the resulting organism.

In the case of Down's syndrome or Trisomy 21, a gamete with (n+1) chromosome is fertilized by a normal gamete (n) to have three copies of chromosome 21.

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