Biological Science

Scott Freeman, Lizabeth Allison, Michael Black

Chapter 21

Genomics and Beyond - all with Video Answers

Educators

Chapter Questions

Problem 1

What is an open reading frame in bacteria?
a. a gene whose function is already known
b. a DNA section that is thought to code for a protein because it is similar to a complementary DNA (cDNA)
c. a DNA section that is thought to code for a protein because it has a start codon and a stop codon flanking hundreds of nucleotides
d. any member of a gene family

Evey Z

Evey Z

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Problem 2

What best describes the logic behind shotgun sequencing?
a. Break the genome into tiny pieces. Sequence each piece. Use overlapping ends to assemble the pieces in the correct order.
b. Start with one end of each chromosome. Sequence straight through to the other end of the chromosome.
c. Use a variety of techniques to identify genes and ORFs. Sequence these segments - not the noncoding and repeated sequences.
d. Break the genome into pieces. Map the location of each piece. Then sequence each piece.

Evey Z

Numerade Educator

Problem 3

A________ is a $2-$ to 6 -base-pair repeated sequence in DNA.
a. LINE
b. restriction site
c. gene duplication
d. microsatellite

Evey Z

Numerade Educator

Problem 4

What is a leading hypothesis to explain the paradox that large, morphologically complex eukaryotes such as humans have relatively small numbers of genes?
a. lateral transfer of genes from other species
b. alternative splicing of mRNAs
c. polyploidy, or the doubling of the genome's entire chromosome complement
d. expansion of gene families through gene duplication

Evey Z

Numerade Educator

Problem 5

What evidence do biologists use to infer that a gene is part of a gene family?

Evey Z

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Problem 6

What are some characteristics of a pseudogene?

Evey Z

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Problem 7

Explain how open reading frames are identified in the genomes of bacteria and archaea. Why is it more difficult to find open reading frames in eukaryotes?

Evey Z

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Problem 8

In a genomics-based search for mutations that caused a patient's cancer, which of the following would provide the most informative comparison with the cancer cell?
a. the average human DNA sequence available from a database
b. the DNA sequence of a noncancerous cell from another person
c. the DNA sequence of a noncancerous cell from the patient
d. the DNA sequence of a different tumor type from another cancer patient

Evey Z

Numerade Educator

Problem 9

Gene density is the number of genes per unit length of DNA. Most often, gene density is expressed as the number of genes per million base pairs (Mbp). Go to Figure $21.4 \mathrm{b}$ and find the approximate number of genes estimated in water fleas and in humans and the size of each genome. What is the gene density per Mbp in water fleas? What is the gene density per Mbp in humans? How much greater is the gene density in water fleas relative to humans?

Evey Z

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Problem 10

In DNA fingerprinting, why is it an advantage to analyze an STR locus with many different repeat length alleles versus an STR locus with only a few different repeat length alleles?

Evey Z

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Problem 11

Explain how microarrays of short, single-stranded DNAs that represent many or all of the exons in a genome are used to document changes in the transcription of genes over time or in response to environmental challenges.

Evey Z

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Problem 12

Explain the concept of homology and how identifying homologous genes helps researchers identify the function of unknown genes.

Evey Z

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Problem 13

Parasites lack genes for many of the enzymes found in their hosts. Most parasites, however, have evolved from free-living ancestors that had larger genomes. Based on these observations, W. Ford Doolittle claims that the loss of genes in parasites represents an evolutionary trend. He summarizes his hypothesis with the quip "use it or lose it." What does he mean?

Evey Z

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Problem 14

According to eyewitness accounts, communist revolutionaries executed Nicholas II, the last czar of Russia, along with his wife and five children, the family physician, and about a dozen servants. Many decades after this event, a grave purported to hold the remains of the royal family was discovered. Biologists were asked to analyze DNA from each adult and juvenile skeleton and determine whether the bodies were indeed those of several young siblings, two parents, and several unrelated adults. If the remains of the family were in this grave, predict how similar the DNA fingerprints would be between the parents, the children, and the unrelated individuals in the grave.

Joanna Quigley

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Problem 15

Pleiotropy (a concept presented in Chapter 14 ) occurs when a mutation in one gene results in many different phenotypes.
Pleiotropy (a concept presented in Chapter 14 ) occurs when a mutation in one gene results in many different phenotypes.
In a study of a gene interaction network, similar to the protein interaction network shown in Figure 21.13 , which type of gene would you predict to exhibit the greatest degree of pleiotropy when mutated?
a. a gene that interacts with one neighbor
b. a gene that has a duplicate copy
c. a gene that is the center of interactions with functionally related genes
d. a gene that is the center of interactions with genes of many different functions

Evey Z

Numerade Educator

Problem 16

One hypothesis for differences between humans and chimps involves differences in gene regulation. A recent study used microarrays to compare the patterns of expression of genes that are active in the brain, liver, and blood of chimpanzees and humans. The overall patterns of gene expression were similar in the liver and blood of the two species, but the expression patterns were strikingly different in the brain. How do these results relate to the hypothesis?

Evey Z

Numerade Educator