Thymine dimers are most commonly caused by which of the following?
U.V. irradiation.
What type of mutation is seen here?
Wild type: 5-TAC AAA ATA CAG CGG-3
Mutation: 5-TAC AAG ATA CAG CGG-3
transition
What kind of DNA lesion does UV energy cause?
pyrimidine dimerisation
Identify two DNA repair mechanisms that remove UV-induced DNA lesions.
Check all that apply.
photoreactivation
nonhomologous end joining
synthesis-dependent strand annealing
nucleotide excision
photoreactivation and nucleotide excision
You have conducted an Ames test on a given compound. Which of the following would be classified as a positive result on the Ames test?
A. His- strain grows on an his- plate.
B. His+ strain grows on an his+ plate.
C. His- strain grows on an his+ plate.
D.
A. His- strain grows on an his- plate.
Given the DNA sequence 5-TAC AAA ATA CAG CGG-3, which of these sequences represents a missense mutation?
A. 5-TAC AAG ATA CAG CGG-3
B. 5-TAC AAA TAC AGC GGG-3
C. 5-TAC AAA ATA CAC CGG-3
D. 5-TAG AAA ATA CAG CGG-3
E. 5-TAC AAA ATA CAG AGG-3
C. 5-TAC AAA ATA CAC CGG-3
because.....CAG->CAC = Gln->His
amino acid change in protein
Tor F.
Tautomers of nucleotide bases are isomers that differ from each other in the location of one hydrogen atom in the molecule.
T
Which nucleotide will base?pair with the enol form of 5?bromouracil?
A. Thymine
B. Cytosine
C. Guanine
D. Adenine
C. Guanine
The enol form of 5?bromouracil forms a base pair with guanine.
Which of the following events could result in a frameshift mutation?
A. Base deletion
B. Tautomeric shift
C. Incorporation of base analogs
D. Point mutation
A. Base deletion
A base deletion would shorten the DNA sequence and change the reading frame of the mRNA.
DNA polymerase is very accurate and rarely makes a mistake in DNA replication. Occasionally, however, an error in replication, known as a ___, is introduced. There are two general categories of point mutations�frameshift mutations (also called ___ or ____
point mutation
frameshifts= base-pair insertions or base-pair deletions
substitution
Generally speaking, which of the following mutations would most severely affect the protein coded for by a gene?
Generally speaking, which of the following mutations would most severely affect the protein coded for by a gene?
A. a base substitution at the
C. a frameshift deletion at the beginning of the gene
A frameshift mutation at the beginning of a gene would affect every codon after the point where the mutation occurred. During protein synthesis, incorrect amino acids would be inserted from the point w
The purpose of the Ames Test is to _______.
A. test the mutagenic effects of chemicals
B. determine whether Salmonella typhimurium
his- mutants can revert to his+
C. determine whether histidine has mutagenic
effects in S. typhimurium
D. study how the live
A. test the mutagenic effects of chemicals
In the Ames Test, the appearance of his+ revertants in the presence of a non-mutagenic control compound indicates that _______.
A. the growth medium contains factors that are
mildly mutagenic
B. liver extract increases the potency of some
mutagens
C. some
C. some of the reversion mutations are not caused by the mutagen being tested
His+ revertants on the control plate are the result of spontaneous mutation.
T or F.
Many chemicals are more mutagenic after being processed in the liver.
T
Many potential mutagens are poorly mutagenic until passing through the liver.
What type of mutation results in a single amino acid substitution?
What type of mutation results in a single amino acid substitution?
A. Missense.
B. A single nucleotide insertion.
C. Silent.
D. Nonsense.
A. missense
Given the sequence of a DNA coding strand, 5'-TAC AAA ATA CAG CGG-3', which of these sequences represents a nonsense mutation?
Given the sequence of a DNA coding strand, 5'-TAC AAA ATA CAG CGG-3', which of these sequences represents a nonsense mutation?
A
A. 5'-TAG AAA ATA CAG CGG-3'
Why is aneuploidy in animals generally detrimental?
A. It results in chromosome segregation errors in
mitosis due to aberrant chromosome numbers.
B. Synthesis of extra chromosomes creates a
metabolic burden that decreases cell viability.
C. It results in
C. It results in an imbalance of gene products from
affected chromosomes, which alters normal
development.
During which stage of mitosis and/or meiosis do homologs segregate?
A. Both anaphase I and II of meiosis
B. Anaphase I of meiosis
C. Anaphase of mitosis
D. Anaphase II of meiosis
B. Anaphase I of meiosis
Assume that an organism exists in which crossing over does not occur, but that all other processes associated with meiosis occur normally. Consider how the absence of crossing over would affect the outcome of meiosis.
If crossing over did not occur, which
There would be less genetic variation among gametes.
Which of the following accurately describes a possible meiotic nondisjunction event?
Which of the following accurately describes a possible meiotic nondisjunction event?
A. Homologs fail to separate during meiosis I.
B. Fusion of gametes results in trisom
A. Homologs fail to separate during meiosis I.
All of the following events occur during normal meiosis except _______.
A. homologous chromosomes separate from one
another during meiosis I
B. one diploid cell produces four haploid cells
C. sister chromatids separate from one another
during meiosis II
D
D. two haploid gametes fuse to form a diploid cell
T or F.
In order to create the possibility of generating a trisomy, nondisjunction must occur during meiosis II.
F
Nondisjunction during either meiosis I or meiosis II creates gametes that will generate trisomies if fertilized.
Separation of sister chromatids occurs _______.
A. at anaphase II in mitosis and anaphase in meiosis
B. in meiosis, but not in mitosis
C. in mitosis, but not in meiosis
D. at anaphase in mitosis and anaphase II in
meiosis
D. at anaphase in mitosis and anaphase II in
meiosis
T or F.
The end result of meiosis is four haploid daughter cells.
T
Novel combinations of genes can arise from _______.
A. reciprocal exchange of DNA between homologs
during prophase II
B. the alignment of chromosomes at Metaphase II
C. reciprocal exchange of DNA between homologs
during prophase I
D. reciprocal exchange o
C. reciprocal exchange of DNA between homologs
during prophase I
If nondisjunction occurs in meiosis II, how many of the four gametes will be aneuploid?
If nondisjunction occurs in meiosis II, how many of the four gametes will be aneuploid?
1, 2, 3, or 4
2
Nondisjunction in meiosis II produces one nullosomic gamete and one disomic gamete. The two products produced by the other meiosis I daughter cell will produce two normal haploid gametes.
Which of the following is a common consequence of a viable trisomy?
A. Reduced fertility
B. Increased rate of cell division
C. Polyploidy
D. Increased cell size
A. Reduced fertility
Trivalent synaptic structures form in meiosis I. Segregation of homologs results in the production of aneuploid gametes.
The parent cell that enters meiosis is diploid, whereas the four daughter cells that result are haploid.
Which statement correctly describes how cellular DNA content and ploidy levels change during meiosis I and meiosis II? (Note: Ignore any effects of cr
C. DNA content is halved in both meiosis I and
meiosis II. Ploidy level changes from diploid to
haploid in meiosis I, and remains haploid in
meiosis II.
During anaphase of both meiosis I and meiosis II, the DNA content (number of copies of chromosomes) in
What dosage compensation mechanism is employed by female placental mammals?
Y-inactivation
synteny
X nondisjunction
X-inactivation
X chromosome crossing over
X-inactivation
How many Barr bodies are found in a normal human female nucleus?
One Barr body.
Two Barr bodies.
Three Barr bodies.
No Barr bodies.
One Barr body
How many Barr bodies are found in a normal male nucleus?
One Barr body.
Two Barr bodies.
Three Barr bodies.
No Barr bodies.
No bar bodies
How is the effective dosage of X-linked gene products balanced in placental mammals between females that carry two X chromosomes and males that carry only a single X chromosome?
A. Genes on the single male X chromosome are expressed at twice the rate of g
C. One X chromosome is randomly inactivated in female somatic cells.
One X chromosome is randomly inactivated early in embryogenesis. This leaves female somatic cells with one copy of the X chromosome that is expressed, which is equivalent to what is foun
What features are shared by genes identified as "hotspots" for mutations?
Genes are often large.
Genes often lack introns.
Genes are typically highly conserved.
Genes are often located near the centromeres.
Genes are often large.
Which type of mutation may result in expression of intronic sequence or loss of part of an exon?
Triplet-repeat expansion mutation
Promoter mutation
Polyadenylation mutation
Splice site mutation
Splice site mutation