Exam 3

Question 1

A mutation changes a codon to another codon that does not change the original amino acid to a different amino acid. This is a

a. silent mutation
b. missense mutation
c. nonsense mutation
d. frameshift mutation

Answer 1

a. silent mutation

Question 2

Which of the following is an example of a somatic mutation?

a. A mutation in an embryonic muscle cell
b. A mutation in a sperm cell
c. A mutation in an adult nerve cell
d. Both a and c

Answer 2

d. Both a and c

Question 3

Which of the following is a cause of spontaneous mutations?

a. 5-bromouracil used for chemotherapy
b. UV light
c. A tautomeric shift that causees mis-base pairing
d. A chemical such as nitrous acid that can change the structure of a base

Answer 3

c. A tautomeric shift that causes mis-base pairing

Question 4

A key event that promotes trinucleotide repeat expansion is

a. chromosome breakage
b. the presence of an AT-rich region
c. the presence of a lesion in the DNA
d. the formation of a hairpin

Answer 4

d. the formation of a hairpin

Question 5

Which of the following is/are possible reason why a mutation may have a positive effect?

a. The mutation is located next to the gene’s promoter
b. The mutation is a translocation that moves the gene from a euchromatic region to a heterochromatic region
c. The mutation is an inversion that moves a gene’s promoter next to the regulatory sequences of a different gene
d. Both b and c

Answer 5

d. Both b and c

Question 6

Let’s suppose that a chemical is a mutagen. If you tested this chemical using the Ames test, there would be ____ colonies on the plates in which the cells had been exposed to the mutagen, because the mutagen converts some of the cells from ____.

a. less, his⁺ to his^-
b. more, his⁺ to his^-
c. less, his^- to his⁺
d. more, his^- to his⁺

Answer 6

d. more, his^- to his⁺

Question 7

Below are 4 steps that occur in the nucleotide excision repair system. What is their correct order?

A. Removal of the damaged region
B. Endonuclease cleavage on either side of the lesion
C. Sensing of a DNA lesion
D. Use of the opposite strand (without a lesion) as a template to make new DNA

Answer 7

C, B, A, D

Question 8

Gene conversion may occur via

a. mismatch repair
b. gap repair synthesis
c. nucleotide excision repair
d. both a and b

Answer 8

d. both a and b

Question 9

According to the Holliday model for homologous recombination, a heteroduplex is formed due to

a. the initial breakage of the DNA at a single location in two different DNA strands
b. the formation of a D loop
c. the migration of a Holliday junction
d. the resolution of the Holliday junction into two separate DNA molecules

Answer 9

c. the migration of a Holliday junction

Question 10

According to the Holliday model for homologous recombination, what is/are the possible end result(s) of the resolution step?

a. Recombinant chromosomes without a heteroduplex region
b. Recombinant chromosomes with a heteroduplex region
c. Nonrecombinant chromosomes with a heteroduplex region
d. Both b and c are possible

Answer 10

d. Both b and c are possible

Question 11

The restriction enzymes shown below cut DNA in the following manner. The slashes indicate where cutting occurs.

BamHI G\GATCC

                                CCTAG\G

EcoRI G\AATTC

                                CTTAA\G     

HaeII GGCGC\C

                               C\CGCGG

PstI CTGCA\G

                               G\ACGTC

Which of these enzymes would generate sticky ends that would be the most stable when they bind to complementary sticky ends?

a. BamHI
b. HaeII
c. EcoRI
d. PstI

Answer 11

b. HaeII

Question 12

Which of the following steps is not needed to make a cDNA (complementary DNA library)?

a. Attach linkers to the cDNA
b. Cut cDNA and vector with a restriction enzyme, and ligate the cDNA into the vector
c. Isolate chromosomal DNA and digest with a restriction enzyme
d. Isolate mRNA and make cDNA using reverse transcriptase and a poly-dT primer

Answer 12

c. Isolate chromosomal DNA and digest with a restriction enzyme

Question 13

During PCR, what is the order of events in a single cycle?

a. Annealing of the primers, denaturation of the DNA, synthesis of complementary strands
b. Annealing of the primers, synthesis of complementary strands, denaturation of the DNA
c. Denaturation of the DNA, synthesis of complementary strands, annealing of the primers
d. Denaturation of the DNA, annealing of the primers, synthesis of complementary strands

Answer 13

d. Denaturation of the DNA, annealing of the primers, synthesis of complementary strands

Question 14

During real-time PCR, why does the level of fluorescence given off by the TaqMan probe decrease over time?

a. Reverse transcriptase cleaves the TaqMan probe, which separates the quencher and the reporter
b. Taq polymerase cleaves the TaqMan probe, which separates the quencher and the reporter
c. Taq polymerase binds to the TaqMan probe and causes its fluorescence to increase
d. As the PCR products accumulate, the Taqman probe binds to more template strands and thereby gives off more fluorescence

Answer 14

b. Taq polymerase cleaves the TaqMan probe, which separates the quencher and the reporter

Question 15

A primer used in dideoxy DNA sequencing is 20 nucleotides long and has the following sequence: 5’-GGATCCATGACTAGTCCGAC-3’. A segment of DNA is cloned into a vector and then the vector DNA is denatured and subjected to dideoxy DNA sequencing method. Below is the DNA sequence from a region of the vector. The primer-annealing site is shown in bold and underlined.

3-CCCGATCGGCCTAGGTACTGATCAGGCTGAATGACT-5’

Based on the sequence above, what would be the size(s) of the band(s) (i.e., the number of nucleotides in each band) in which dideoxyT had been added to the sequencing reaction?

a. 1, 2, and 5
b. 21, 22, and 25
c. 3 and 7
d. 23 and 27

Answer 15

b. 21, 22, and 25

Question 16

Researchers conducted Northern blotting on a sample of cells from mouse kidney, brain, and liver using a probe that is complementary to a gene that encodes a glucose transporter. All of the samples were taken from the same mouse. The following results were obtained:

(shows kidney smaller strand than brain and liver)

If we assume that equal amounts of total cellular RNA was loaded into each lane, which of the following statements is true?

a. Brain cells express this gene at the highest level
b. The pre-mRNA is alternatively spliced
c. The gene in the kidney cells has suffered a deletion
d. All of the above are false

Answer 16

b. The pre-mRNA is alternatively spliced

Question 17

Which component of the CRISPR-Cas system causes it to bind to a target gene?

a. Cas9 protein
b. Spacer region of sgRNA
c. TracrRNA region of the sgRNA
d. Linker region of the sgRNA

Answer 17

b. Spacer region of the sgRNA

Question 18

Glofish are zebrafish that contain a gene from either a coral or jellyfish. This is an example of

a. gene replacement
b. gene addition
c. a gene knockout
d. both a and b

Answer 18

b. gene addition

Question 19

Reproductive cloning is a method of using the genetic material from somatic cells to produce offspring that are genetically identical to the donor parent. How does this approach work?

a. A somatic cell, such as a mammary cell, is made totipotent by treating it with hormones
b. A somatic cell, such as a mammary cell, has its nucleus removed and then the nucleus from an oocyte is inserted into it
c. A somatic cell, such as a mammary cell, is fused with an egg cell that had its nucleus removed
d. A sperm and egg cell are fused with a somatic cell (e.g., a mammary cell) that had its nucleus removed

Answer 19

c. A somatic cell, such as a mammary cell, is fused with an egg cell that had its nucleus removed

Question 20

One method of molecular pharming involves the synthesis of human proteins into the milk of cows. As an example, let’s consider the production of human antibodies in cow’s milk. Which of the following components would not be needed to achieve this goal?

a. Coding sequence of a human antibody gene
b. Beta-lactoglobulin promoter from a cow
c. Enhancer sequences from a human antibody gene
d. Cow oocyte

Answer 20

c. Enhancer sequences from a human antibody gene

Question 21

When two different genes are homologous, this means

a. they have identical sequences
b. they are derived from the same ancestral gene
c. they are found in all living species
d. they are found in multiple copies

Answer 21

b. they are derived from the same ancestral gene

Question 22

A DNA microarray is a slide that is dotted with

a. mRNA from a sample of cells
b. fluorescently labeled cDNA
c. known sequences of DNA
d. known cellular proteins

Answer 22

c. known sequences of DNA

Question 23

If a computer program is designed to recognize a specific regulatory element such as a GRE (glucocorticoid response element), this is an example of

a. pattern recognition
b. search by signal, also known as sequence recogntion
c. search by content (e.g., codon bias)
d. both a and b

Answer 23

b. search by signal, also known as sequence recognition

Question 24

For a rare genetic disorder that is equally probable in males and females, the concordance for identical twins is 91%. Which of the following is/are a possible reason(s) why the concordance value between identical twins is not 100%?

a. The disorder may not be completely penetrant
b. In some cases, the disorder may be due to a new mutation in one of the twins
c. Identical twins may have inherited different types of mitochondria
d. Both a and b are possible

Answer 24

d. both a and b are possible

Question 25

Below is a pedigree involving a human disease that is inherited in a simple Mendelian manner. Which of the following patterns is this pedigree consistent with?

(male has it, all his daughters and two sons have it, their daughters/sons have it)

a. autosomal recessive only
b. X-linked recessive only
c. autosomal dominent only
d. both a and c

Answer 25

c. autosomal dominant only

Question 26

Haploinsufficiency follows a ____ pattern of inheritance. In this case, the protein encoded by the disease-causing allele is ____

a. recessive, inactive
b. recessive, overactive
c. dominant, inactive
d. dominant, overactive

Answer 26

c. dominant, inactive

Question 27

Which of the following would not be consistent with the idea that a human disease has a genetic component?

a. It has a particular age of onset
b. It is less likely to occur in relatives living apart than in relatives living together
c. A correlation is found between the presence of a mutation in a particular gene and the occurrence of the disease
d. All of the above are consistent

Answer 27

b. It is less likely to occur in relatives living apart than in relatives living together

Question 28

Which of the following is not an example of personalized medicine?

a. Prescribing medicines or activities to prevent a disease (such as heart disease) based on a person’s genotype
b. Using a certain type of chemotherapy based on the genetic characteristics of a tumor
c. Giving a patient a certain dosage of a drug based on their genotype
d. Giving a patient a drug that was synthesized by genetically modified yeast

Answer 28

d. Giving a patient a drug that was synthesized by genetically modified yeast

Question 29

The BRCA-1 gene in humans is a tumor-suppressor gene that can play a role in certain types of inherited breast cancers. Which of the following statements regarding this gene is false?

a. A pre-disposition to develop breast cancer due to a BRCA-1 mutation displays a dominant inheritance pattern in a pedigree
b. The mutation in BRCA-1 that promotes cancer is a loss-of-function mutation
c. At the cellular level, the BRCA-1 mutation is recessive
d. A deletion of the BRCA-1 gene would not promote breast cancer

Answer 29

d. A deletion of the BRCA-1 gene would not promote breast cancer

Question 30

The Rb gene is a tumor suppressor gene that encodes the Rb protein that negatively regulates E2F. Which of the following genotypes would promote cancer at the cellular level? Note: A superscript with a minus sign denotes a loss-of-function allele.

a. Rb^- Rb^- E2F^- E2F^-
b. Rb⁺ Rb^- E2F^- E2F^-
c. Rb⁺ Rb^- E2F⁺ E2F^-
d. Rb^- Rb^- E2F⁺ E2F^-

Answer 30

d. Rb^- Rb^- E2F⁺ E2F^-

Question 31

When a gene pool changes from generation to generation, this process is called

a. natural selection
b. evolution
c. inbreeding
d. both a and b

Answer 31

b. evolution

Question 32

In a population in Hardy-Weinberg equilibrium, the percentage of individuals exhibiting a recessive disorder is 1%, which is the same as 0.01. What is the frequency of heterozygotes? (p² + 2pq + q² = 1)

a. 0.99
b. 0.32
c. 0.18
d. 0.09

Answer 32

c. 0.18

Question 33

Darwinian fitness is a measure of

a. the relative allele frequencies
b. reproductive succes
c. heterozygosity of the gene pool
d. population size

Answer 33

b. reproductive succes

Question 34

Which of the following would promote polymorphism?

a. Negative frequency-dependent selection
b. Diversifying (disruptive) selection
c. Heterozygote advantage
d. All of the above

Answer 34

d. All of the above

Question 35

Within a particular population, darkly colored rats are more likely to survive than more lightly colored individuals. This scenario is likely to result in

a. directional selection
b. stabilizing selection
c. disruptive selection (also called diversifying selection)
d. balancing selection

Answer 35

a. directional selection

Question 36

A gene exists in two alleles and the heterozygote has the highest fitness. This scenario is likely to result in

a. directional selection
b. stabilizing selection
c. disruptive selection (also known as diversifying selection)
d. balancing selection

Answer 36

d. balancing selection

Question 37

Within a particular population, darkly colored moths are more likely to survive in forests whereas lightly colored individuals are more likely to survive in meadows. This scenario is likely to result in

a. directional selection
b. stabilizing selection
c. disruptive selection (also called diversifying selection)
d. balancing selection

Answer 37

c. disruptive selection (also called diversifying selection)

Question 38

Which of the following is a common mechanism of genetic drift?

a. The bottleneck effect
b. The founder effect
c. Negative-frequency dependent selection
d. Both a and b

Answer 38

d. Both a and b

Question 39

Which of the following is not expected to occur as a result of bidirectional migration?

a. It tends to reduce allele frequency differences between two populations
b. It tends to increase the rate of genetic drift
c. It can enhance genetic diversity within a population because new mutations in one population can be introduced to neighboring populations
d. All of the above are expected to occur as a result of bidirectional migration

Answer 39

b. It tends to increase the rate of genetic drift

Question 40

What is the inbreeding coefficient for VI-1? (Family tree is more of a ring, count all members connecting the ring except the individual)

a. 0
b. 0.0020
c. 0.0039
d. 0.0078

Answer 40

c. 0.0039

Question 41

For a quantitative trait that is polygenic, which of the following would tend to promote a continuum of phenotypes?

a. Increasing the number of genes that affect the trait
b. Decreasing the effects of environmental variation
c. Increasing the mutation rate
d. Both a and b

Answer 41

a. Increasing the number of genes that affect the trait

Question 42

Which of the following statistics is computed as a squared deviation?

a. Mean
b. Correlation coefficient
c. Variance
d. Standard deviation

Answer 42

c. Variance

Question 43

In a strain of tomatoes, the variance for fruit weight is 441g², and the mean weight is 412g. How heavy would a tomato have to be to rank in the bottom 0.15%?

a. Equal to or less than 391g
b. Equal to or less than 370g
c. Equal to or less than 349g
d. Equal to or less than 63g

Answer 43

c. Equal to or less than 349g

Question 44

Researchers determined the correlation coefficient (r) for egg weight between chickens and those of their female offspring in two different populations. In both cases, r = 0.49. One population had an N value of 38 and the other had an N value of 5. Which of the following statements is true.

a. Only the r value in which N = 5 is statistically significant
b. Only the r value in which N = 38 is statistically significant
c. both r values are statistically significant
d. Neither r value is statistically significant

Answer 44

b. Only the r value in which N = 38 is statistically significant

Question 45

A QTL (quantitative trait locus) is a ____ where one or more genes affecting a quantitative trait are ____

a. site in a cell, located
b. site on a chromosome, located
c. site in a cell, expressed
d. site on a chromosome, expressed

Answer 45

b. site on a chromosome, located

Question 46

When certain genotypes are preferentially found in a particular environment, this is termed

a. a genotype-environment association
b. a genotype-environment interaction
c. the additive effects of alleles
d. both a and b

Answer 46

a. a genotype-environment association

Question 47

Which of the following statements regarding heritability is/are true?

a. Heritability applies to a specific population raised in a particular environment
b. Heritability in the narrow sense takes into account all types of genetic variance
c. Heritability is a measure of the amount that genetics contributes to the outcome of a trait
d. Both a and c are true

Answer 47

a. Heritability applies to a specific population raised in a particular environment

Question 48

In a population of rabbits, the correlation between weight for mothers and their adult sons is 0.28. What is the narrow sense heritability for weight in this population? Note: h_N² = r_obs/r_exp

a. 0.14
b. 0.34
c. 0.56
d. 1.12

Answer 48

c. 0.56

Question 49

The mean weight of cows in a population is 520 kg. Animals with a mean weight of 540 kg are used as parents and produce offspring that have a mean weight of 535 kg. What is the narrow-sense heritability (h_N²) for body weight in this population of cows? Note: _N² = (X_o − X)/(X_p − X)
Where
X is the mean weight of the starting population
X_o is the mean weight of the offspring
X_p is the mean weight of the selected parents

a. 0.25
b. 0.5
c. 0.75
d. 1.0

Answer 49

c. 0.75

Question 50

With regard to heterosis, which of the following scenarios is/are consistent with the overdominance hypothesis?

a. AA and Aa have the same fitness, and aa has a lower fitness
b. AA and aa have the same fitness, and Aa has a lower fitness
c. A1A2 has a higher fitness compared to A1A1 and A2A2
d. Both b and c are correct

Answer 50

c. A1A2 has a higher fitness compared to A1A1 and A2A2