Deck 18: Genomes and Their Evolution

Question 1

Unequal crossing over during prophase I can result in one sister chromosome with a deletion and another with a duplication. A mutated form of hemoglobin, so-called hemoglobin Lepore, exists in the human population. Hemoglobin Lepore has a deleted series of amino acids. If this mutated form was caused by unequal crossing over, what would be an expected consequence?

A) If it is still maintained in the human population, hemoglobin Lepore must be selected for in evolution.
B) There should also be persons whose hemoglobin contains two copies of the series of amino acids that is deleted in hemoglobin Lepore.
C) Each of the genes in the hemoglobin gene family must show the same deletion.
D) The deleted gene must have undergone exon shuffling.
E) The deleted region must be located in a different area of the individual's genome.

Answer 1

B

Question 2

Which of the following is a representation of gene density?

A) Humans have 2,900 Mb per genome.
B) C. elegans has ~20,000 genes.
C) Humans have ~20,000 genes in 2,900 Mb.
D) Humans have 27,000 bp in introns.
E) Fritillaria has a genome 40 times the size of a human genome.

Answer 2

C

Question 3

Humans have 23 pairs of chromosomes. In contrast, chimpanzees have 24 pairs of chromosomes and lack any pair resembling the long human chromosome 2 pair; instead, chimpanzees have two pairs of medium-sized chromosomes. What is the most likely explanation for these differences in the human and chimpanzee genomes?

A) The common ancestor of humans and chimpanzees had 24 pairs of chromosomes, and at some point in the human lineage, two chromosomes fused end to end, providing some selective advantage.
B) The common ancestor of humans and chimpanzees had 23 pairs of chromosomes, but when chimpanzees evolved, one of the chromosomes broke in half.
C) At some point in evolution, human ancestors and chimpanzee ancestors were able to mate and produce fertile offspring, making a new species.
D) Chromosome breakage resulted in additional centromeres being made, allowing meiosis to proceed successfully.
E) Transposable elements transferred significantly large segments of the chromosomes to new locations.

Answer 3

A

Question 4

What characteristic of short tandem repeat DNA makes it useful for DNA fingerprinting?

A) The number of repeats varies widely from person to person or animal to animal.
B) The sequence of DNA that is repeated varies significantly from individual to individual.
C) The sequence variation is acted upon differently by natural selection in different environments.
D) Every racial and ethnic group has inherited different short tandem repeats.

Question 5

Which of the following can be duplicated in a genome?

A) DNA sequences above a minimum size only
B) DNA sequences below a minimum size only
C) entire chromosomes only
D) entire sets of chromosomes only
E) sequences, chromosomes, or sets of chromosomes

Question 6

Which procedure is not required when the shotgun approach to sequencing is modified as sequencing by synthesis, in which many small fragments are sequenced simultaneously?

A) use of restriction enzymes
B) sequencing each fragment
C) cloning each fragment into a plasmid
D) ordering the sequences
E) PCR amplification

Question 7

In humans, the embryonic and fetal forms of hemoglobin have a higher affinity for oxygen than that of adults. This is due to

A) nonidentical genes that produce different versions of globins during development.
B) identical genes that generate many copies of the ribosomes needed for fetal globin production.
C) pseudogenes, which interfere with gene expression in adults.
D) the attachment of methyl groups to cytosine following birth, which changes the type of hemoglobin produced.
E) histone proteins changing shape during embryonic development.

Question 8

What is bioinformatics?

A) a technique using 3-D images of genes to predict how and when they will be expressed
B) the application of computational methods to the storage and analysis of biological data
C) software programs available from NIH to design and synthesize genes
D) a series of search programs that allow a student to identify which labs around the world are trying to sequence the genome of a given species
E) a procedure that uses software to order DNA sequences in a variety of comparable ways

Question 9

What is metagenomics?

A) genomics as applied to a species that most typifies the average phenotype of its genus
B) the sequence of one or two representative genes from several species
C) the sequencing of only the most highly conserved genes in a lineage
D) sequencing DNA from a group of species from the same ecosystem
E) genomics as applied to an entire phylum

Question 10

The comparison between the number of human genes and those of other animal species has led to many conclusions, including that

A) the density of the human genome is far higher than in most other animals.
B) the number of proteins expressed by the human genome is far more than the number of its genes.
C) most human DNA consists of genes for protein, tRNA, rRNA, and miRNA.
D) the genomes of other organisms are significantly smaller than the human genome.

Question 11

In order to determine the probable function of a particular sequence of DNA in humans, what might be the most reasonable approach?

A) Prepare a knockout mouse without a copy of this sequence and examine the mouse phenotype.
B) Genetically engineer a mouse with a copy of this sequence and examine its phenotype.
C) Look for a reasonably identical sequence in another species, prepare a knockout of this sequence in that species, and look for the consequences.
D) Prepare a genetically engineered bacterial culture with the sequence inserted and assess which new protein is synthesized.
E) Mate two individuals heterozygous for the normal and mutated sequences.

Question 12

A recent study compared the H. sapiens genome with that of Neanderthals. The results of the study indicated that there was a mixing of the two genomes at some period in evolutionary history. The data that suggested this were

A) some Neanderthal sequences not found in humans.
B) a number of modern H. sapiens with Neanderthal sequences.
C) Neanderthal Y chromosomes preserved in the modern population of males.
D) mitochondrial sequences common to both groups.

Question 13

A microarray known as a GeneChip, with most of the human protein-coding genetic sequences, has been developed to aid in the study of human cancer by first comparing two to three subsets of cancer subtypes. What kind of information might be gleaned from this GeneChip to aid in cancer prevention?

A) information about whether or not a patient has this type of cancer prior to treatment
B) evidence that might suggest how best to treat a person's cancer with chemotherapy
C) data that could alert patients to what kind of cancer they were likely to acquire
D) information about which parent might have provided a patient with cancer-causing genes
E) information on cancer epidemiology in the United States or elsewhere

Question 14

What is proteomics?

A) the linkage of each gene to a particular protein
B) the study of the full protein set encoded by a genome
C) the totality of the functional possibilities of a single protein
D) the study of how amino acids are ordered in a protein
E) the study of how a single gene activates many proteins

Question 15

Which of the following most correctly describes the whole-genome shotgun technique for sequencing a genome?

A) genetic mapping followed immediately by sequencing
B) physical mapping followed immediately by sequencing
C) cloning large genome fragments into very large vectors such as YACs, followed by sequencing
D) cloning fragments from many copies of an entire chromosome, sequencing the fragments, and then ordering the sequences
E) cloning the whole genome directly, from one end to the other

Question 16

Fragments of DNA have been extracted from the remnants of extinct woolly mammoths, amplified, and sequenced. These can now be used to

A) introduce into relatives, such as elephants, certain mammoth traits.
B) clone live woolly mammoths.
C) study the relationships among woolly mammoths and other wool-producers.
D) understand the evolutionary relationships among members of related taxa.
E) appreciate the reasons why mammoths went extinct.

Question 17

A multigene family is composed of

A) multiple genes whose products must be coordinately expressed.
B) genes whose sequences are very similar and that probably arose by duplication.
C) the many tandem repeats such as those found in centromeres and telomeres.
D) a gene whose exons can be spliced in a number of different ways.
E) a highly conserved gene found in a number of different species.

Question 18

When does exon shuffling occur?

A) during splicing of DNA
B) during DNA replication
C) during meiotic recombination
D) during post-translational modification of proteins
E) during faulty DNA repair

Question 19

Homeotic genes contain a homeobox sequence that is highly conserved among very diverse species. The homeobox is the code for that domain of a protein that binds to DNA in a regulatory developmental process. Which of the following would you then expect?

A) that homeotic genes are selectively expressed over developmental time
B) that a homeobox-containing gene has to be a developmental regulator
C) that homeoboxes cannot be expressed in nonhomeotic genes
D) that all organisms must have homeotic genes
E) that all organisms must have homeobox-containing genes

Question 20

Why might the cricket genome have 11 times as many base pairs as that of Drosophila melanogaster?

A) The two insect species evolved in very different geologic eras.
B) Crickets have higher gene density.
C) Drosophila are more complex organisms.
D) Crickets must have more noncoding DNA.
E) Crickets must make many more proteins.

Question 21

One of the characteristics of retrotransposons is that

A) they code for an enzyme that synthesizes DNA using an RNA template.
B) they are found only in animal cells.
C) they generally move by a cut-and-paste mechanism.
D) they contribute a significant portion of the genetic variability seen within a population of gametes.
E) their amplification is dependent on a retrovirus.

Question 22

Use Figure 18.1 to answer the next few questions.
Figure 18.1
Types of DNA sequences in the human genome.
The pie chart in Figure 18.1 represents the relative frequencies of the following in the human genome:
I. repetitive DNA unrelated to transposons
II. repetitive DNA that includes transposons
III. unique noncoding DNA
IV. introns and regulatory sequences
V. exons
Which region is occupied by exons only (V)?

A) A
B) B
C) C
D) D
E) E

Question 23

Homeotic genes

A) encode transcription factors that control the expression of genes responsible for specific anatomical structures.
B) are found only in Drosophila and other arthropods.
C) are the only genes that contain the homeobox domain.
D) encode proteins that form anatomical structures in the fly.
E) are responsible for differentiation in muscle cells.

Question 24

Two eukaryotic proteins have one domain in common but are otherwise very different. Which of the following processes is most likely to have contributed to this similarity?

A) gene duplication
B) alternative splicing
C) exon shuffling
D) histone modification
E) random point mutations

Question 25

Two eukaryotic proteins are identical except for one domain in each protein, and these two domains are completely different from each other. Which of the following processes is most likely to have contributed to this difference?

A) gene duplication
B) alternative splicing
C) exon shuffling
D) histone modification
E) random point mutations

Question 26

Use Figure 18.2 to answer the next few questions.
Figure 18.2 shows a diagram of blocks of genes on human chromosome 16 and the locations of blocks of similar genes on four chromosomes of the mouse.
Which of the following represents another example of the same phenomenon as that shown in Figure 18.2?

A) the apparent centric fusion between two chromosome pairs of primates such as chimps to form the ancestor of human chromosome 2
B) the difference in the numbers of chromosomes in five species of one genus of birds
C) the formation of several pseudogenes in the globin gene family subsequent to human divergence from other primates
D) the high frequency of polyploidy in many species of angiosperms

Question 27

Use Figure 18.2 to answer the next few questions.
Figure 18.2 shows a diagram of blocks of genes on human chromosome 16 and the locations of blocks of similar genes on four chromosomes of the mouse.
The movement of these blocks suggests that

A) during evolutionary time, these sequences have separated and have returned to their original positions.
B) DNA sequences within these blocks have become increasingly divergent.
C) sequences represented have duplicated at least three times.
D) chromosomal translocations have moved blocks of sequences to other chromosomes.
E) higher mammals have more convergence of gene sequences related in function.

Question 28

Bioinformatics includes all of the following except

A) using computer programs to align DNA sequences.
B) analyzing protein interactions in a species.
C) using molecular biology to combine DNA from two different sources in a test tube.
D) developing computer-based tools for genome analysis.
E) using mathematical tools to make sense of biological systems.

Question 29

Use the following information to help you answer the next few questions.
Multigene families include two or more nearly identical genes or genes sharing nearly identical sequences. A classical example is the set of genes for globin molecules, including genes on human chromosomes 11 and 16.
How might identical and obviously duplicated gene sequences have gotten from one chromosome to another?

A) by normal meiotic recombination
B) by normal mitotic recombination between sister chromatids
C) by transcription followed by recombination
D) by chromosomal translocation
E) by deletion followed by insertion

Question 30

Use Figure 18.1 to answer the next few questions.
Figure 18.1
Types of DNA sequences in the human genome.
The pie chart in Figure 18.1 represents the relative frequencies of the following in the human genome:
I. repetitive DNA unrelated to transposons
II. repetitive DNA that includes transposons
III. unique noncoding DNA
IV. introns and regulatory sequences
V. exons
Which region includes Alu elements and LI sequences?

A) A
B) B
C) C
D) D
E) E

Question 31

Several of the different globin genes are expressed in humans, but at different times in development. What mechanism could allow for this?

A) exon shuffling
B) intron activation
C) pseudogene activation
D) differential translation of mRNAs
E) differential gene regulation over time