Question

Chimpanzees, gorillas, and orangutans all have 48 chromosomes, whereas humans have 46. Human chromosome 2 is a large, metacentric chromosome with G-banding patterns that closely match those found on two different acrocentric chromosomes of the apes. What would best explain these findings?

a) Infection by a primate virus created a new chromosome when the viral DNA became a permanent part of the genome. Humans were not affected by this virus, so they did not acquire the extra chromosome.
b) A Robertsonian translocation took place in a human ancestor, creating a large metacentric chromosome from the two long arms of the ancestral acrocentric chromosomes. The other small chromosome produced by this translocation was lost.
c) A nonreciprocal translocation and subsequent fusion of the chromosomal fragments created a genome of 46 chromosomes without the loss of any genetic information.
d) Meiotic nondisjunction gave rise to a nullisomic gamete. The fusion of two nullisomic gametes produced the ancestor of the human species with 46 chromosomes instead of 48.

Answer 1

Option B

Step-by-step explanation:

A Robertsonian translocation took place in a human ancestor, creating a large metacentric chromosome from the two long arms of the ancestral acrocentric chromosomes in a balanced form such that there is no effect on the individual. The other small chromosome produced by this translocation was lost.

This structure réarrangement usually results in the reduction in the number of chromosomes.