genetics ch 13
2) Both the change in the genetic material and the process by which the change occurs is referred to as a/an: a) Mutation b) Error c) Reparation d) Mutation and Error e) All of these
a
1) Living cells contain numerous enzymes that constantly scan DN, searching for damaged or incorrectly paired nucleotides. When detected, these defects are corrected by: a) DNA scanning enzymes b) RNA polymerase c) DNA repair enzymes d) DNA polymerase e) Ligase
c
18) Mutations that result in no gene product or totally nonfunctional gene products are called: a) Isomers b) Isoalleles c) Null alleles d) Lethal alleles e) Forward alleles
c
23) Chemical mutations that change the position of hydrogen atoms in a nitrogenous base are known as: a) Isomer mutations b) Isomer shifts c) Tautomeric shifts d) Isomer mutations and Isomer shifts e) All of these
c
24) Which base pair combinations can form when nitrogenous bases are present in their rare imino or enol states? a) A:T b) C:G c) A:C d) A:T and C:G e) C:G and A:C
c
27) Base-pair substitutions involving the replacement of a purine with a pyrimidine and vice versa are called: a) Isomers b) Transitions c) Transversions d) Inversions e) None of these
c
28) Base-pair additions and deletions that alter the reading frame of all subsequent base-pair triplets are collectively referred to as: a) Inversions b) Transversions c) Frameshift mutations d) Point mutations e) Codon mutations
c
30) Which type of mutation can be caused by acridine dyes? a) Transversions b) Transitions c) Frameshift d) Chromosomal e) All of these
c
33) Bruce Ames constructed a mutagenicity test which initially missed carcinogens which were noncarcinogenic to the tester strains. Why? a) Tester strains were more resistant to the mutagenic effects of the carcinogen than eukaryotes b) Not all carcinogens are mutagens c) Potential carcinogens needed to be modified in eukaryotes before they were mutagenic d) Histidine biosynthesis was inhibited by the presence of the carcinogens. e) All of these
c
39) Which of the following molecules carries out single-strand assimilation? a) XPA b) MutD c) RecA d) RecBCD e) UvrD
c
40) Which of the following enzymes performs light dependent repair? a) DNA gyrase b) DNA polymerase c) DNA photolyase d) RNA polymerase e) DNA helicase
c
11) Which of the following is a known mutagen? a) UV light b) Thalidomide c) Irradiation d) UV light and Irradiation e) All of these
e
31) Which of the following statements about radiation induced mutations is true? a) X rays, cosmic rays, and UV rays are all classified as ionizing radiation b) Ionizing radiation results in raising electrons to an atom's outer orbitals, a state referred to as excitation c) In mammals, chronic irradiation is as effective in inducing mutations as acute irradiation d) UV radiation results in the formation of purine dimers and purine hydrates e) X rays can result in gross changes of chromosome structure, such as large deletions, duplications and inversions
e
32) Which of the following is not exhibited Fragile X syndrome? a) An X chromosome which contains up to 1000 copies of the CCG repeat at one site b) Inherited mental retardation c) A correlation between the number of repeats and the severity of the defects d) The phenomenon of "anticipation" e) Decreasing numbers of the CCG repeat in successive generations
e
5) Which of the following is considered a point mutation? 1. Substitution of the base A for the base C 2. Deletion of the base T 3. Insertion of the base G a) 1 b) 2 c) 3 d) 1 and 2 e) All of these
e
7) Which of the following organisms has never experienced a genetic mutation? a) E. coli b) Humans c) Drosophila d) T4 virus e) All of these have experienced genetic mutations
e
10) Mutations that occur without a known cause are known as: a) Spontaneous mutations b) Induced mutations c) Harmful mutations d) Adaptive mutations e) None of these
a
13) A mutation that provides a selective advantage to the mutant organism when grown in the environment in which it originated is known as a/an: a) Adaptive mutation b) Forward mutation c) Suppressor mutation d) Missense mutation e) Nonsense mutation
a
20) A mutation that has no phenotypic effect on the organism is known as: a) Neutral mutation b) Null mutation c) Isomer mutation d) Lethal allele e) All of these
a
22) Which of the following mutations or techniques was not used in deducing the pathway of T4 morphogenesis? a) Auxitrophic mutations b) Temperature-sensitive mutations c) Suppressor-sensitive mutations d) Electron micrsoscopy e) Biochemical analysis
a
42) Which of the following proteins is vital to the process of recombination? a) RecA b) CroA c) HemA d) Gyrase e) Topoisomerase
a
14) Gene X undergoes a mutation which converts it from wild-type to mutant. Later, a second mutation in the genome in gene Y occurs which causes the wild-type phenotype of the first gene (gene X) to be restored. Respectively, what are the appropriate designations for the two mutational events? a) Forward mutation, back mutation b) Forward mutation, suppressor mutation c) Reverse mutation, back mutation d) Reverse mutation, suppressor mutation e) Reverse mutation, forward mutation
b
17) Genes containing mutations with no effect on phenotype or small effects that can be recognized only by special techniques are called: a) Isomers b) Isoalleles c) Null alleles d) Lethal alleles e) Forward alleles
b
19) Which of the following mutations is described correctly? a) Phenylketonuria: An autosomal recessive disease resulting in the overproduction of phenyalanine hydroxylase b) Alkaptonuria: An autosomal recessive disease which inactivates homogentistic acid oxidase c) Albinism: An autosomal dominant trait, which blocks the synthesis of melanin from tyrosine d) Tyrosinemia: A lack of a tyrosine catabolic enzyme, which leads to an decrease in tyrosine in the blood and urine e) All of these
b
21) Mutations that are lethal in one environment but viable in another are known as: a) Lethal mutations b) Conditional lethal mutations c) Null mutations d) Isoallele mutations e) All of these
b
26) Base-pair substitutions in which the purine in one strand of DNA is replaced with a different purine, and the pyrimidine in the complementary strand is replaced with a different pyrimidine are known as: a) Isomers b) Transitions c) Transversions d) Inversions e) None of these
b
29) Some mutagenic agents only affect replicating DNA; others are mutagenic to replicating and non-replicating DNA. Which of the following mutagens does not belong to the second class? a) Alkylating agents b) Base analogs c) Nitroud acid d) All of these e) None of these
b
3) An organism that exhibits a novel phenotype resulting from a mutation is called a: a) Wild type b) Mutant c) Positive phenotype d) Negative phenotype e) None of these
b
35) Which of the following DNA alterations can be corrected by light-dependent repair? a) Methylation b) Thymine dimers c) Mismatched basepairing d) Hydroxylation e) Inversions
b
36) Which of the following statements about excision repair is correct? a) Base excision repair is initiated by DNA glycosylases that recognize abnormal deoxyriboses in DNA b) Nucleotide excision repair removes large regions of DNA via an exonuclease which cuts on either side of the damaged bases c) E. coli exonuclease activity is carried out by uvrA, uvrB, and uvrC, and the resulting gap is filled in by DNA Pol III d) DNA glycosylases cleave the altered nucleoside (base and sugar) from the DNA backbone creating an apurinic or apyrimidinic site e) In humans, a mechanism similar to E. coli is carried out where the protein XPA acts as the exonuclease.
b
37) Which of the following statements about the mismatch repair pathway is not correct? a) MutH contains a GATC-specific endonuclease activity b) Cleavage of the unmethylated strand only occurs 3' to the mismatch c) This system of repair utilizes MutH, MutL, MutS, and UvrD d) The repair system can distinguish the template strand from the newly synthesized strand e) All of these are correct
b
43) Many of the currently popular models of crossing over were derived from a model proposed by: a) James Watson b) Robin Holliday c) Francis Crick d) Rosalind Franklin e) None of these
b
44) X-shaped recombination intermediates formed from Holliday model recombination are known as: a) Tai molecules b) Chi forms c) Holliday forms d) X forms e) None of these
b
6) Which of the following statements is not true about mutation? a) Mutation refers to both change in the genetic material and the process by which the change occurs b) Point mutations involve changes at specific sites in a gene c) If a mutation occurs in a somatic cell, the mutant phenotype will be passed on to the offspring of that organism d) The intrinsic mistake frequency in nucleotide selection during DNA polymerization is 10-5 e) None of these
c
8) Which cell type experiences germinal mutations? a) Squamous Epithelial b) Chondrocytes c) Gametes d) Cuboidal Epithelial e) Columnar Epithelial
c
12) Mutation is a random and non-adaptive process. This was first proven by: a) Lysenko and Lamarck, using the removal of mouse tails as an environmental stress. b) Joshua and Esther Lederberg, using the removal of mouse tails as an environmental stress. c) Lysenko and Lamarck, using replica plated E. coli and streptomycin as an environmental stress. d) Joshua and Esther Lederberg, using replica-plated E. coli and streptomycin as an environmental stress e) Mutation is not a random, nonadaptive process.
d
15) Restoration of the wild type phenotype in a mutant organism can result from which of the following types of mutations? a) Back mutation b) Suppressor mutation c) Forward mutation d) Back mutation and Suppressor mutation e) Suppressor mutation and Forward mutation
d
16) Hemoglobin is a model system to illustrate the deleterious effects of mutations. Which of the following statements about deleterious mutations in human hemoglobin genes is false? a) Hemoglobin A and hemoglobin S differ at only one amino acid position b) In hemoglobin S, the substitution of valine for glutamic acid causes an aggregation of hemoglobin molecules not found in hemoglobin A c) The molecular difference between hemoglobin A and hemoglobin S was identified by protein sequence before nucleotide sequence d) The valine to glutamic acid substitution is the only amino acid change so far identified in the β chain of hemoglobin e) Homozygous (Hbsb/Hbsb) leads to severe hemolytic anemia, which is often fatal.
d
25) What is the net effect of a tautomeric shift event, and the subsequent replication required to segregate the mismatched base pair? 1. A:T to G:C base pair substitution 2. G:C to A:T base pair substitution 3. A:C to G:T base pair substitution a) 1 b) 2 c) 3 d) 1 and 2 e) All of these
d
34) Bruce Ames and coworkers developed an inexpensive and sensitive method for testing the mutagenicity of chemicals with histidine auxotrophic mutants of: a) E. coli b) S. aureus c) B. subtilis d) Salmonella e) C. elegans
d
38) Which DNA repair mechanism can be template-independent and require polymerase activity? a) Post-replication repair b) Mismatch repair c) Light-dependent repair d) Error-prone repair e) Excision repair
d
4) Mutations that involve changes at specific sites in a gene are referred to as: a) Frameshift mutations b) Nonsense mutations c) Misssense mutations d) Point mutations e) None of these
d
41) Which of the following disease is not associated with a defect in a DNA repair pathway? a) Bloom syndrome b) Werner syndrome c) Rothmund-Thomson syndrome d) Cystic Fibrosis e) Fanconi anemia
d
45) Gene conversion of Neurospora requires recombination and which of the following events? a) Reversion b) Suppression c) Excision repair d) Heteroduplex formation e) Inversion
d
9) If a mutation occurs in a somatic cell, the resulting mutant phenotype will occur: a) Only in the Individual cell b) Only in the progeny from that individual cell c) Only in the offspring of that organism d) In both the progeny of that individual cell and the individual cell itself e) Neither the progeny from that individual cell or the offspring of the organism
d
