Chapter 19 genetics

After screening a colony of bacteria for mutations in a given gene, you discover 100 mutant colonies out of 3 million total colonies. What is the mutation frequency for this gene in the population? 1.0 x 105 1.0 x 10-5 3.0 x 105 3.3 x 10-5

3.3 x 10-5

Most TNRE repeats involve expansion of which codon? GAA CAG ATG CCC Any codon containing three of the same bases

CAG

A temporary change in the conformation of a nitrogenous base is called ______. Depurination A tautomeric shift Deamination None of the answers are correct

A tautomeric shift

Photolyase in yeast is an example of what kind of DNA repair mechanism? Recombinational repair Direct repair Base excision repair Mismatch repair Nucleotide excision repair

Direct repair

The results of the replica plating experiments by the Lederbergs supported which theory? Random mutation theory Physical adaptation theory Both theories Neither theory

Random mutation theory

An example of a base analog would be EMS Nitrous acid 5BU Nitrogen mustards Acridine dyes

5BU

There is a spectrum of syndromes in humans known as Xeroderma pigmentosum. The individuals that have XD most commonly have mutations in their nucleotide excision DNA repair mechanisms that make them particularly susceptible to environmental mutagens such as UV light. Individuals have to be careful with how much sunlight they are exposed to since they have an extremely elevated chance for developing skin cancer. There have been several cell lines that have been established from XD patients that can be studied in tissue culture. In an experiment several different cell lines of unknown origin were tested for their ability to undergo unscheduled DNA synthesis (UDS), an assay for DNA repair. In this assay the amount of radioactive nucleotides that are incorporated into DNA after the cell sustains a mutagenic event are measured. The amount of radioactivity incorporated is measured by the number of counts per minute (CPM). Below is a table from such an experiment. Which cell line is most likely from XD patient(s)? A B C D

A

An example of a mutagen that integrates into the double-helix of DNA resulting in the inhibition of DNA replication would be EMS Nitrous acid 5BU 2-amino purine Acridine dyes

Acridine dyes

An example of a suppressor mutation would be An intragenic mutation that restores the inactive protein's structure An intergenic mutation that increases the activity of a protein performing a different function as the mutated protein An intergenic mutation that activates a transcription factor that increases the expression of a normal protein A mutation that suppresses cell growth

An intragenic mutation that restores the inactive protein's structure

Mutations that change the configuration of a protein at a specific temperature are called ____ mutations. Neutral Beneficial Deleterious Conditional

Conditional

The complete loss of either a guanine or adenine from DNA is an example of _____. Depurination Tautomeric shifts Deamination Demethylation

Depurination

Spontaneous mutations include Depurination, deamination, errors in DNA replication UV light, radiation, deamination, depurination UV light, radiation, deamination, errors in replication UV light, errors in DNA replication, deamination, depurination

Depurination, deamination, errors in DNA replication

The wild-type eye color of Drosophila is red. A single-base mutation can occur that produces a white eye color. What statement is correct regarding this mutation? It is an example of a mutation that alters protein function Individuals with white eyes have a reversion mutation It would be an example of a silent mutation The white eyed phenotype is called an example of a neutral mutation.

It is an example of a mutation that alters protein function

Which repair mechanism identifies daughter strands by methylation? Recombinational repair Direct repair Base excision repair Mismatch repair Nucleotide excision repair Nonhomologous end joining (NHEJ)

Mismatch repair

Which repair mechanism utilizes MutL, MutH, and MutS proteins in E. coli? Recombinational repair Direct repair Base excision repair Mismatch repair Nucleotide excision repair Nonhomologous end joining (NHEJ)

Mismatch repair

Which repair mechanism often leads to deletions in chromosomes? Recombinational repair Direct repair Base excision repair Mismatch repair Nucleotide excision repair Nonhomologous end joining (NHEJ)

Nonhomologous end joining (NHEJ)

A culture of E. coli bacteria is used to establish several subcultures. Each subculture is then plated and individual colonies that grow on the agar plates are then tested for their sensitivity to the bacteriophage T1. There is a spectrum of sensitivities where some plates have a high number of resistant colonies and some plates had very few. This data supports which theory? Physiological adaptation theory Random mutation theory Both theories Neither theory

Random mutation theory

Select the correct statement regarding rate of mutation. Rates of spontaneous mutation per cell generation typically range from 10-5 to 10-9 Mutation rates are consistent across species Mutation rates are not influenced by environmental conditions Mutation rates are constant

Rates of spontaneous mutation per cell generation typically range from 10-5 to 10-9

A translocation that moves a gene from an area of euchromatin to heterochromatin would typically cause a(n) _______ in the expression of the gene. Reduction Increase Gene expression would remain the same

Reduction

Which types of mutations are least likely to be subjected to natural selection? Silent Missense Nonsense Insertion

Silent

Anticipation is associated with which type of mutation? Nonsense mutations Up-promoter mutations Intergenic suppressors TNRE mutations None of the answers are correct

TNRE mutations

Beechdrops is a parasitic plant that cannot perform photosynthesis but relies on its host the Beech tree. However, Beechdrops still retains many if not all of the genes for photosynthesis. Snapdragons and gladiolas are common garden flowers that rely on their ability to perform photosynthesis. If you were to compare the gene sequences for these three plants for ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) a protein necessary for photosynthesis what would you predict? The differences between gladiolas and snapdragons would most likely be silent mutations while those in beechdrops may be silent or missense Since these three plants are not highly related the sequences for RuBisCO would be very different between them The differences between gladiolas and snapdragons would most likely be in the second nucleotide of codons while beechdrops would have a higher number of mutations in the third nucleotide of the different codons The differences between gladiolas and snapdragons would most likely be missense mutations while those in beechdrops may be silent or missense

The differences between gladiolas and snapdragons would most likely be silent mutations while those in beechdrops may be silent or missense

What would be a set of anticipated results from a "Lederberg" experiment? Total number of colonies on a plate: 1500 Total number of resistant colonies on replica plate with T1: 150 Total number of colonies on a plate: 1500 Total number of resistant colonies on replica plate with T1: 1500 Total number of colonies on a plate: 500 Total number of resistant colonies on replica plate with T1: 1500 Total number of colonies on a plate: 1500 Total number of resistant colonies on replica plate with T1: 0

Total number of colonies on a plate: 1500 Total number of resistant colonies on replica plate with T1: 150

How does position effect influence gene expression? Point mutations in promoters frequently occur by this mechanism Translocations may result in a promoter that is normally used for one gene now controlling an entirely different gene. Since this mechanism relies on recombination it relies on the positioning of one allele so that it is under the control of the other allele. Translocations always result in a gene being recombined into an area of heterochromatin.

Translocations may result in a promoter that is normally used for one gene now controlling an entirely different gene.

In the following sequence of DNA, the italicized base has been mutated. What type of mutation is this? 5' - G A T C T C C G A A T T - 3' original strand 5' - G A T C T C C C A A T T - 3' mutated strand Transition Transversion Neither

Transversion

Select the example of an induced mutational mechanism. DNA replication errors Tautomeric shifts of nucleic acid bases Aberrant recombination UV light Transposable elements

UV light

In the nucleotide excision repair system, which of the following proteins is responsible for recognizing a thymine dimer to be repaired? UvrA/UvrB UvrC UvrD UvrE

UvrA/UvrB

A mutagen is an agent that can alter the structure of DNA and cause mutations. a depurinated base. a DNA polymerase without a 5' to 3' exonuclease. a deaminated base.

an agent that can alter the structure of DNA and cause mutations.

The mechanism for reactive oxygen species to cause mutation is bases are oxidized to a variety of different products which might pair with a different base than the original base would have. thymine bases are dimerized which causes a break in the DNA which is not repaired correctly. the reactive oxygen species stabilize different tautomeric forms of the bases causing inappropriate pairing. guanine is depurinated by the reactive oxygen species and if it is not repaired can result in any base being inserted.

bases are oxidized to a variety of different products which might pair with a different base than the original base would have.

The difference between the polymerases used in translesion synthesis repair and general DNA replication is the polymerase used in translesion synthesis has a pocket that can accommodate the lesions while DNA pol III's pocket cannot. there is no real difference between the polymerases except that the translesional polymerase is not part of the replication complex. the polymerase used in translesion synthesis has a pocket that cannot accommodate the lesions, that is part of the mechanism by which the lesions are removed. the polymerase used to remove the lesion has a modified nucleotide binding pocket allowing for mispairing of nucleotides.

the polymerase used in translesion synthesis has a pocket that can accommodate the lesions while DNA pol III's pocket cannot.