A person with trisomy 21 has an extra copy of chromosome 21. What happened during meiosis that caused the person to get three copies of chromosome 21 instead of two copies?

a) nondisjunction

b) genetic recombination

c) crossing-over

d) binary fission

Question

A person with trisomy 21 has an extra copy of chromosome 21. What happened during meiosis that caused the person to get three copies of chromosome 21 instead of two copies?

a) nondisjunction

b) genetic recombination

c) crossing-over

d) binary fission

anonymous · Answer

The answer would be nondisjunction because this occurs when a homologous chromosomes or sister chromatids fails to separate properly during cell division.