Principles of Genetics: Exam 1

Certain repair systems operate to correct problems in DNA. Which of the following statements is correct for the photoreactivation repair system? a. small segments of DNA are cleaved from the strand, then DNA poly I replaces the missing bases. b. it corrects base substitutions by replacing the incorrect base with the correct base. c. it adds 2 bases to a single base addition mutation in order to correct the reading frame. d. it breaks the bonds between adjacent thymine (T) bases to restore proper bonding between strands. e. it is found only in prokaryotic organisms.

d. it breaks the bonds between adjacent thymine (T) bases to restore proper bonding between strands

Which of the following are two mutagens that would be classified as base analogs? a. acridine orange and proflavin b. hydroxyurea and peroxidase c. ethylmethane sulfonate and ethylmethylketone peroxide d. ultraviolet light and cosmic radiation e. 5-bromouracil and 2-aminopurine

e. 5-bromouracil and 2-aminopurine

Transposons, or jumping genes, are DNA elements that move within the genome. In which organismic groups are transposons found? a. bacteria b. ancient bacteria c. mammals d. eukaryotes e. all organismic groups

e. all organismic groups

In lecture we discussed mutation frequencies both within and among species. Which of the following is correct with respect to that discussion? a. the mutation frequency of a specific gene is the same in all species that have that gene. b. mutation frequencies are the same for different genes within a species. c. mutation frequenciesare always higher in prokaryotes compared to eukaryotes. d. mutation frequencies in humans are so low they can't be measured. e. different genes in the same species have different mutation frequencies.

e. different genes in the same species have different mutation frequencies.

Which of the following mutagens is matched correctly with its action? a. mustard gasses are base analogs b. 5-Bromouracil is an alkylating agent c. 2-Amino purine is an adduct-forming agent d. acetaldehyde is a free radicle e. ethidium bromide is an intercalating agent

e. ethidium bromide is an intercalating agent

A class of mutations that results in multiple contiguous amino acid changes in proteins is likely to be which of the following? a. transition b. base analog c. recombinant d. transversion e. frameshift

e. frameshift

A mutation occurs in a bacterial cell which results in a nonfunctional DNA polymerase III molecule. Which of the following would most likely occur because of this mutation? a. this can't be determined since it would depend on whether it was a transversion or a transition mutation. b. only the 3'----5' strand could be synthesized. c. it would result in a tautomeric shift. d. no priming sequence would be produced, so DNA replication would not occur. e. neither DNA strand could be replicated.

e. neither DNA strand could be replicated

In bacteria and eukaryotes, a mutation is when ________. a. the nucleotide sequence in an mRNA molecule is directly changed b. the amino acid sequence in a protein molecule is directly changed c. DNA is unable to be replicated d. the expression of a gene changes without the DNA sequence being changed e. the nucleotide sequence in a DNA molecule is directly changed

e. the nucleotide sequence in a DNA molecule is directly changed

Which enzyme is responsible for proofreading during replication? a. DNA polymerase b. DNA ligase c. DNA glycosylase d. RNA polymerase

a. DNA polymerase

A point mutation occurs such that a codon is changed from AGA to AGC. Which term describes this mutation? a. Transversion mutation b. Frameshift mutation c. Insertion mutation d. Transition mutation

a. Transversion mutation

Germ cell mutations ________. a. are usually found in every cell of the next generation b. are of no consequence to the next generation c. affect somatic cell function in the current generation d. are only seen in females e. are the cause of testicular cancer

a. are usually found in every cell of the next generation

Based on our "bunny trail" lecture, how would you categorize a mutation in a plant species that caused a reduction in height due to greatly reduced activity in the growth hormone? a. morphological mutation. b. behavioral mutation. c. lethal mutation. d. conditional mutation. e. bad mutation.

a. morphological mutation.

Which of the following is not correct with respect to mutations? a. regardless of the species, mutations happen abundantly in nature. b. mutation frequencies vary from species to species. c. spontaneous mutations are randomly produced. d. regardless of the species, the mutation rate for a particular gene is always different. e. mutations are the primary cause of genetic variation

a. regardless of the species, mutations happen abundantly in nature.

What is meant by the term photoreactivation repair? a. A process in which DNA damage can be completely reversed if cells are exposed to light in the visible spectrum. b. A process in which UV-induced DNA damage can be partially reversed if cells are briefly exposed to light in the blue range of the visible spectrum. c. A process in which UV-induced DNA damage can be completely reversed if cells are briefly exposed to light in the violet range of the visible spectrum. d. A process in which any DNA damage can be partially reversed if cells are briefly exposed to light in the blue range of the visible spectrum.

b. A process in which UV-induced DNA damage can be partially reversed if cells are briefly exposed to light in the blue range of the visible spectrum.

During mismatch repair, an exonuclease enzyme creates a nick in the backbone of the unmethylated DNA strand near the mismatch. a. True b. False

b. False

Which of the following is correct with respect to tautomeric shifts? a. these occur only when a base analogue was substituted for a normal base during DNA replication. b. a shift in the atoms (proton shift) arrangement in the bases, result in base pair changes during DNA replication. c. these are the primary source of adaptive mutations. d. these are caused in bacteria when neither DNA poly III or the secondary proofreading system corrected a base mismatch. e. these only occur when the bacteria is exposed to blue light.

b. a shift in the atoms (proton shift) arrangement in the bases, result in base pair changes during DNA replication.

Let's assume that a mutation occurred in a bacterial cell. The mutation was a change in the base sequence in the gene which produces one of the components of the primase molecule. It resulted in the production of a nonfunctioning primase molecule. What effect would this mutation have on the organism? a. it would result in replication of both DNA strands to be much slower than normal. b. it would prevent DNAfrom being replicated. c. only one of the two DNA strands would serve as a template so there would be no increase in the number of double helices. d. transcription would occur as normal so this wouldn't be a "real" genetic mutation. e. it wouldhave no effect on any cell process.

b. it would prevent DNAfrom being replicated.

Mutations that arise in nature, from no particular artificial agent, are called ________. a. induced mutations b. spontaneous mutations c. chromosomal losses d. cosmic mutations e. nutritional mutations

b. spontaneous mutations

How do base analogs produce mutations? a. they add a base directly to an existing DNA chain causing frameshift mutations. b. they are incorporated into DNA as normal nucleotides, but through tautomeric shifts pair with incorrect bases. c. they remove large portions of the DNA molecule causing deletions to occur. d. they act directly to change DNA nucleotides to other bases that pair incorrectly. e. they change thymine nucleotides to uracil, changing the chain from DNA to RNA.

b. they are incorporated into DNA as normal nucleotides, but through tautomeric shifts pair with incorrect bases.

If the normal DNA sequence is AAAAA and the mutant is AATAA, this mutation would be called a: a. transition. b. transversion. c. frameshift. d. inversion. e. mistake (technically correct, but no credit for this answer)

b. transversion

Thymine dimers form when ________. a. two thymines adjacent to each other are deleted from the DNA sequence b. two thymines on the same strand and adjacent to each other bind together c. two thymines on separate strands of DNA bind to together d. two thymines on the same strand but not adjacent to each other bind together e. two thymines are inserted into a DNA sequence

b. two thymines on the same strand and adjacent to each other bind together

Most mutations are thought to be deleterious. Why, then, is it reasonable to state that mutations are essential to the evolutionary process? a. Most mutations are deleterious. To prevent diseases due to mutation humans product drugs which affect healthy cells and cause their evolution. b. Most mutations are deleterious and there is little evidence demonstrating mutations have contributed to the evolutionary process. c. All mutations may not be deleterious. Few beneficial mutations will provide a basis for possible differential propagation of the variation, and so of the evolutionary process. d. Actually all mutations are deleterious. An organism with fewer mutations survives in evolutionary process. e. Evolution can occur without inherited variation for adaptive traits; therefore mutation does not contribute significantly to evolution.

c. All mutations may not be deleterious. Few beneficial mutations will provide a basis for possible differential propagation of the variation, and so of the evolutionary process.

Generally speaking, which of the following mutations would most severely affect the protein coded for by a gene? a. a base substitution at the beginning of the gene b. a base substitution at the end of the gene c. a frameshift deletion at the beginning of the gene d. a frameshift deletion at the end of the gene

c. a frameshift deletion at the beginning of the gene

A mutation that changes an amino acid-coding codon to a stop codon is classified as what kind of mutation? a. missense b. conditional c. nonsense d. silent e. neutral

c. nonsense

Mutations which arise in nature, from no particular artificial agent, are called: a. natural mutations d. chromosomal mutations b. induced mutations e. cosmic mutations c. spontaneous mutations

c. spontaneous mutations

A photoreactivation repair system is thought to operate in both prokaryotes and eukaryotes to correct what type of problem in DNA? a. tautomeric shifts b. transition mutations c. thymine dimers d. transversion mutations e. U replacement of T in DNA

c. thymine dimers

All of the following mutagenic events occur spontaneously EXCEPT __________. a. tautomerization b. depurination c. deamination d. alkylation

d. alkylation

Tautomeric shifts ________. a. are known to cause insertion or deletion mutations b. allow pyrimidines to bind to pyrimidines c. allow purines to bind to purines d. can cause missense mutations due to mispairings e. are likely to cause frameshifts

d. can cause missense mutations due to mispairings