Question

is the result of nondisjunction, resulting in an extra x chromosome in males. a klinefelter syndrome b achondroplasia c phenylketonuria d cystic fibrosis

Explanation:

Klinefelter syndrome occurs due to nondisjunction (failure of chromosomes to separate properly during cell division), leading to an extra X chromosome (XXY) in males. Achondroplasia is a genetic disorder causing dwarfism due to a gene mutation. Phenylketonuria is an inborn error of metabolism from a gene defect affecting phenylalanine metabolism. Cystic fibrosis is a genetic disorder from mutations in the CFTR gene affecting the lungs and digestive system. Only Klinefelter syndrome involves an extra X - chromosome due to nondisjunction.

Answer:

A. Klinefelter syndrome