26.4 An organism’s evolutionary history is documented in its genome

Question 1

42) A researcher wants to determine the genetic relatedness of several breeds of dog (Canis
familiaris). The researcher should compare homologous sequences of
that are
__________
known to be __________.
A) carbohydrates; poorly conserved
B) fatty acids; highly conserved
C) lipids; poorly conserved
D) proteins or nucleic acids; poorly conserved
E) amino acids; highly conserved

Answer 1

D) proteins or nucleic acids; poorly conserved

Question 2

43) Concerning growth in genome size over evolutionary time, which of these does not belong
with the others?
A) orthologous genes
B) gene duplications
C) paralogous genes
D) gene families

Answer 2

A) orthologous genes

Question 3

44) Nucleic acid sequences that undergo few changes over the course of evolutionary time are
said to be conserved. Conserved sequences of nucleic acids
A) are found in the most crucial portions of proteins.
B) include all mitochondrial DNA.
C) are abundant in ribosomes.
D) are proportionately more common in eukaryotic introns than in eukaryotic exons.
E) comprise a larger proportion of pre-mRNA (immature mRNA) than of mature mRNA.

Answer 3

C) are abundant in ribosomes.

Question 4

45) Species that are not closely related and that do not share many anatomical similarities can
still be placed together on the same phylogenetic tree by comparing their
A) plasmids.
B) chloroplast genomes.
C) mitochondrial genomes.
D) homologous genes that are poorly conserved.
E) homologous genes that are highly conserved.

Answer 4

E) homologous genes that are highly conserved.

Question 5

48) Which kind of DNA should provide the best molecular clock for gauging the evolutionary
relatedness of several species whose common ancestor became extinct billions of years ago?
A) that coding for ribosomal RNA
B) intronic DNA belonging to a gene whose product performs a crucial function
C) paralogous DNA that has lost its function (i.e., no longer codes for functional gene product)
D) mitochondrial DNA
E) exonic DNA that codes for a non-crucial part of a polypeptide

Answer 5

A) that coding for ribosomal RNA

Question 6

49) A phylogenetic tree constructed using sequence differences in mitochondrial DNA would
be most valid for discerning the evolutionary relatedness of
A) archaeans and bacteria.
B) fungi and animals.
C) Hawaiian silverswords.
D) sharks and dolphins
E) mosses and ferns.

Answer 6

C) Hawaiian silverswords.

Question 7

50) The lakes of northern Minnesota are home to many similar species of damselflies of the
genus Enallagma that have apparently undergone speciation from ancestral stock since the
last glacial retreat about 10,000 years ago. Sequencing which of the following would
probably be most useful in sorting out evolutionary relationships among these closely
related species?
A) nuclear DNA
B) mitochondrial DNA
C) small nuclear RNA
D) ribosomal RNA
E) amino acids in proteins

Answer 7

B) mitochondrial DNA

Question 8

51) Which statement represents the best explanation for the observation that the nuclear DNA
of wolves and domestic dogs has a very high degree of homology?
A) Dogs and wolves have very similar morphologies.
B) Dogs and wolves belong to the same order.
C) Dogs and wolves are both members of the order Carnivora.
D) Dogs and wolves shared a common ancestor very recently.
E) Convergent evolution has occurred.

Answer 8

D) Dogs and wolves shared a common ancestor very recently.

Question 9

52) The reason that paralogous genes can diverge from each other within the same gene pool,
whereas orthologous genes diverge only after gene pools are isolated from each other, is
that
A) having multiple copies of genes is essential for the occurrence of sympatric speciation in the wild.
B) paralogous genes can occur only in diploid species; thus, they are absent from most prokaryotes.
C) polyploidy is a necessary precondition for the occurrence of sympatric speciation in the wild.
D) having an extra copy of a gene permits modifications to the copy without loss of the original gene product.

Answer 9

D) having an extra copy of a gene permits modifications to the copy without loss of the original gene product.

Question 10

53) If the genes of yeast are 50% orthologous to those of humans, and if the genes of mice are
99% orthologous to those of humans, then what percentage of the genes of fish might one
validly predict to be orthologous to the genes of humans?
A) 10%
B) 30%
C) 40%
D) 50%
E) 80%

Answer 10

D) 50%

Question 11

55) What is true of gene duplication (NOTE: gene duplication is a process that is distinct from
DNA replication)?
A) It is a type of point mutation.
B) Its occurrence is limited to diploid species.
C) Its occurrence is limited to organisms without functional DNA-repair enzymes.
D) It is most similar in its effects to a deletion mutation.
E) It can increase the size of a genome over evolutionary time.

Answer 11

E) It can increase the size of a genome over evolutionary time.

Question 12

65) Which of these is the best explanation for the high degree of sequence homology observed
in Exon I among these five species?
A) It is the most-upstream exon of this gene.
B) Due to alternative gene splicing, this exon is often treated as an intron.
C) It codes for a polypeptide domain that has a crucial function.
D) These five species must actually constitute a single species.
E) This exon is rich in G-C base pairs; thus, is more stable.

Answer 12

C) It codes for a polypeptide domain that has a crucial function.