Question

Down syndrome (Trisomy 21) and Klinefelter's syndrome (XXY) are both a result of an extra chromosome due to which type of mutation?
Responses

Frameshift
Frameshift

Deletion
Deletion

Nondisjunction
Nondisjunction

Insertion

Answer 1

Both Down syndrome (Trisomy 21) and Klinefelter's syndrome (XXY) are results of an extra chromosome due to **nondisjunction**. Nondisjunction refers to the failure of homologous chromosomes or sister chromatids to separate properly during cell division, leading to gametes with an abnormal number of chromosomes. If such a gamete contributes to fertilization, the resulting zygote will have an extra chromosome.