Eukaryote genomes vary in size and base sequence. Variation between species is much larger than variation within a species, and not all DNA codes for proteins.
Analysis of the genome of primates reveals many DNA segments that have been duplicated. It is possible to deduce the stage in evolution at which segmental duplications (SDs) occurred by comparing human and other primate genomes. Human-specific SDs occurred after humans and chimpanzees diverged. Human-chimpanzee shared SDs occurred after the common human-chimpanzee ancestor diverged from gorillas and so on. It is possible to estimate the rates at which SDs occurred during evolution using knowledge of when the primates changed. In the chart the bars indicate numbers of shared SDs and the line shows estimates of the rate of SDs per millions of years (Myr).
State the number of SDs that can be found in humans but not in other primates.
State the rate of SDs after the divergence of macaques from the other primates, giving the units.
Outline the trends in the rate of SDs occurring since the separation of orangutans from other primates.
Explain how the number of human-chimpanzee shared SDs can be the lowest despite the rate of SDs per millions of years being the highest.
A few SDs were found in humans and gorillas but not chimpanzees. Suggest how this might have occurred.