Biology (Raven), 10th Edition

Chapter 24: Genome Evolution


A comparison of mouse and rat genomes reveals a smaller ratio of nonsynonymous-to-synonymous amino acid changes than found in a comparison of humans and chimps. This is because:
A)of differences in mutation rates.
B)fewer nonsynonymous mutations have been removed by natural selection in primates than in mice and rats.
C)more nonsynonymous mutations have been removed by natural selection in primates than in mice and rats.
D)of unknown causes.
E)of more gene duplication in primates than in mice and rats.
Following an allopolyploid event there is often unequal chromosome loss in which the genome of one parent is lost at a greater rate than that of the other. What is a plausible explanation for this?
A)Preferential segregation of chromosomes into gametes during meiosis.
B)Different rates of genome replication.
C)There is no known reason.
D)Unequal crossing over.
E)Meiotic checking and repair mechanisms.
When a gene has been duplicated, what usually happens?
A)The duplicate gains a new function.
B)The total function of the ancestral gene is divided among the two copies.
C)The duplicate loses function due to mutation.
D)It is likely to duplicate again.
E)All of the above.
Some ancestral genes become inactivated as they acquire mutations and are termed
Chimps and humans have 98.7% sequence similarity of their DNA. What, then accounts for the significant differences between humans and chimps?
A)This difference is large enough to adequately explain the differences between chimps and humans.
B)The same genes are transcribed differently; in different tissues and at different times.
C)Different patterns of gene transcription activity.
D)It is unknown at the present time.
E)None of the above
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