Final answer:
The fusion of two chromosomes from a common ancestor with chimpanzees formed human chromosome 2, and a pericentric inversion in chromosome 18 played a role in human evolution, altering gene positions and expression.
Step-by-step explanation:
The discussion of Human Evolution Chromosome 2 pertains to a significant event in human evolution, the fusion of two separate chromosomes found in chimpanzees into what is now known as chromosome 2 in humans. After humans diverged from their common ancestor with chimpanzees, a series of genetic rearrangements took place. One such event was a pericentric inversion on chromosome 18, which has been suggested to contribute to the evolutionary history of humans. According to the provided options, the correct answer to the question posed is: b. Two separate chromosomes underwent a pericentric inversion, then fused to form chromosome 2 in humans. This fusion is a hallmark of human evolution that distinguishes our genome from that of our closest genetic relatives. Furthermore, specific genes such as ROCK1 and USP14 became repositioned and expressed differently as a result of the inversion, potentially influencing important aspects of cellular function and contributing to the divergence of humans from other primates.