Question

Which disease is attributed to nondisjunction? A) hemophilia B) Down's syndrome C) cystic fibrosis D) sickle-cell anemia

Answer 1

Step-by-step explanation:

Down's sydrome. In Down's sydrome, an extra 21st chromosome results, because of a nondisjunction in meiosis.

Answer 2

Down's syndrome

Step-by-step 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.