Biology (Raven), 9th Edition

Chapter 24: Genome Evolution

Post-Test

1
Repetitive DNA is often:
A)"Junk" DNA.
B)Retrotransposon DNA.
C)Eliminated.
D)The majority of animal DNA.
E)All of the above.
2
Why do humans have nine times the amount of DNA than pufferfish but about the same number of genes?
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.
3
Why has the genome of the malarial parasite Plasmodium falciparum been particularly difficult to sequence?
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
4
How can sequencing bacterial genomes help to improve crops?
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)Lessons learned from the bacterial genomes can be used in studying plant species.
E)All of the above
5
Genomes of different organisms evolve at different rates. This is thought to be due to:
A)different mutation rates.
B)different population sizes.
C)unknown causes.
D)different selection pressures.
E)differences in generation times.
6
Why do most polyploidy species tend to have even numbers of chromosomes?
A)Most plant species have even numbers to start with.
B)Polyploids with an even number of chromosomes are more likely to have a regular meiosis than those with an odd number, and so are more likely to be fertile.
C)There is elimination of extra chromosomes after a polyploid event to make the number even.
D)Polyploids do NOT tend to have even numbers any more than odd numbers.
E)The cause is unknown.
7
The living great apes (orangutans, gorillas, chimpanzees) all have 24 chromosomes while humans have 23. What accounts for this difference?
A)Homo sapiens has lost a chromosome.
B)A chromosome was gained in the lineage leading to the Great Apes.
C)Two chromosomes fused in humans.
D)A chromosome underwent fission into two in the lineage leading to the great apes.
E)None of the above
8
Sequence comparisons indicate that chimp DNA is _____ % similar to human DNA?
A)95
B)100
C)99
D)80
E)75
9
Nonprotein coding DNA comprises about 30% of the genome in animals. What is the prevailing opinion about the function of this DNA?
A)It has no function; it is "junk".
B)It plays a structural role in chromosomes.
C)It has an unknown function.
D)It contains regulatory RNA sequences.
E)It contains regulatory DNA sequences.
10
There is a correlation between genome size and the number of genes in an organism.
A)True
B)False
11
Why does comparison of distantly related genomes offer clues for causes of disease?
A)They have well-known genomes.
B)It does not; you should compare closely related organisms.
C)Conserved sequences, coding for critical proteins, are easier to distinguish as there has been more divergence over time at nonconserved sites.
D)Both 1 and 3
E)None of the above.
12
Why are model plants, such as Arabidopsis, important to study for crop improvement?
A)They have well-known genomes.
B)Highly conserved genes in model systems can be characterized and used to identify counterparts in commercial species.
C)Genes can be modified and then transferred to crop species.
D)All of the above.
E)None of the above.
13
A surprising and hopeful finding about T. cruzi and two other insect-borne pathogens
A)is that they are highly diverged and therefore necessitate different modes of treatment.
B)is that they have a recent common ancestor.
C)is that they produce proteins that mimic human proteins.
D)is that they have polyploidy.
E)None of the above
14
Polypoidy in plants
A)is very rare.
B)never occurs.
C)only occurs in the laboratory.
D)results in nonfertile offspring always.
E)is ubiquitous.
15
Duplicated ancestral genes are called
A)Paralogues
B)Polyploids
C)Aneuploids
D)Orthologues
E)Pseudogenes
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