Biology, Eighth Edition (Raven)

Chapter 24: Genome Evolution

Post Test

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: (p. 474)
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? (p. 479)
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
When a gene has been duplicated, what usually happens? (p. 479)
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
Chimps and humans have 98.7% sequence similarity of their DNA. What, then accounts for the significant differences between humans and chimps? (p. 483)
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)There are differences in methylation of crucial genes.
D)It is unknown at present.
E)none of the above
Repetitive DNA is often: (p. 484)
A)"junk" DNA.
B)retrotransposon DNA.
D)the majority of animal DNA.
E)all of the above
Why do humans have nine times the amount of DNA than pufferfish but about the same number of genes? (p. 484)
A)Humans have longer exons than in pufferfish.
B)Humans have longer introns than in pufferfish.
C)Humans have more "junk" DNA.
D)Humans have more chromosomes.
E)Humans have more transcribed regions.
Why has the genome of the malarial parasite Plasmodium falciparum been particularly difficult to sequence? (p.485)
A)It is very large.
B)It is very small.
C)It has a high proportion of A and T making it hard to distinguish one portion of the genome from the next.
D)It has a high proportion of repetitive DNA.
E)none of the above
How can sequencing bacterial genomes help to improve crops? (p. 486)
A)They have well-known genomes.
B)by genetically modifying harmful bacteria to make them benign
C)It may be possible to insert genes from bacteria that may protect crops from disease.
D)all of the above
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