Biology, Eighth Edition (Raven)

Chapter 24: Genome Evolution

Pre Test

Genomes of different organisms evolve at different rates. This is thought to be due to: (p. 474)
A)different mutation rates.
B)different population sizes.
C)unknown causes.
D)differences in generation times.
Why do most polyploidy species tend to have even numbers? (p. 477)
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)The cause is unknown.
The living great apes (orangutans, gorillas, chimpanzees) all have 24 chromosomes while humans have 23. What accounts for this difference? (p. 480)
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
Sequence comparisons indicate that chimp DNA is _____ % similar to human DNA? (p. 483)
Nonprotein coding DNA comprises about 30% of the genome in animals. The function of this DNA is thought to be: (p. 484)
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
True or False: There is a correlation between genome size and the number of genes in an organism. (p. 484)
Why does comparison of distantly related genomes offer clues for causes of disease?(p.485)
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 a and c
E)none of the above
Why are model plants, such as Arabidopsis, important to study for crop improvement? (p. 486)
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
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