Question 1

Barbara McClintock discovered mobile elements in corn by analyzing the genetic behavior of two elements,Ds and Ac.The interplay between these two elements has become one of the most interesting stories of discovery in the field of genetics.How do Ds and Ac interact?

Accepted Answer

Ds is a non-autonomous mobile genetic element that can only move if Ac is present in the genome. On the other hand, Ac is an autonomous mobile element that can move independently of Ds. Therefore, both elements interact by ensuring the movement of Ds is dependent on the presence of Ac in the genome.

Question 2

How was it determined that X-rays are mutagenic?

Accepted Answer

H.J.Muller determined that a direct relationship occurred between X-linked recessive lethals and X-ray dose in Drosophila.

Question 3

Mutations may exert a variety of effects on living systems.List at least three categories of mutations based on their biological effects.

Accepted Answer

morphological mutations,nutritional or biochemical mutations,behavioral mutations,regulatory mutations,lethal mutations,conditional mutations

Question 4

A class of mutations that results in multiple contiguous amino acid changes in proteins is likely to be which of the following?

Accepted Answer

Frameshift mutations result in a shift in the reading frame of the mRNA, which can cause multiple contiguous amino acid changes in the protein. Base analogs, transversions, transitions, and recombinants do not necessarily result in multiple contiguous amino acid changes.

Question 5

Under which condition(s)might one have an amino acid substitution in a protein that does not result in an altered phenotype?

Accepted Answer

The answer of Under which condition(s)might one have an amino...

Question 6

Which of the following name two mutagens that would be classified as base analogs?

Accepted Answer

5-bromouracil and 2-amino purine are both base analogs that can substitute for thymine and adenine in DNA, respectively, leading to errors in replication and potentially causing mutations.

Question 7

Nutritional mutations can be defined as ________.

Accepted Answer

Nutritional mutations are mutations that prevent a microorganism from synthesizing a particular nutrient and therefore require it to be provided in the medium. Specifically, nutritional mutations referred to as auxotrophs are unable to grow on minimal medium but can grow on complete medium, whereas prototrophs can grow on minimal medium. Therefore, choice A is the best answer as it accurately defines nutritional mutations.

Question 8

DNA may be damaged from the by-products of normal cellular aerobic respiration.Name three of these electrophilic oxidants that are generally classified as reactive oxidants.

Accepted Answer

The answer of DNA may be damaged from the by-products...

Question 9

Some bacterial transposons,known as Tn elements,are larger than insertion sequences (IS elements)and contain protein-coding genes that have human health significance.What might such a bacterial transposon contain?

Accepted Answer

Bacterial transposons that contain protein-coding genes with human health significance often carry drug resistance genes. These genes can confer resistance to antibiotics, which can make treating bacterial infections more difficult.

Question 10

Two formal terms used to describe categories of mutational nucleotide substitutions in DNA are ________.

Accepted Answer

Transversions and transitions are the two formal terms used to describe categories of mutational nucleotide substitutions in DNA. Transversions occur when a purine is substituted by a pyrimidine or vice versa, while transitions occur when a purine is replaced by another purine or a pyrimidine is replaced by another pyrimidine. Option A, B, D, and E do not accurately describe these categories.

Question 11

Transposons,or jumping genes,are DNA elements that move within the genome.In which organismic groups are transposons found?

Accepted Answer

Transposons, or "jumping genes," are found across all organismic groups, including bacteria, eukaryotes, mammals, and ancient bacteria. This widespread presence underscores their fundamental role in genetic variation and evolution.

Question 12

Assume that a new mutation occurs in the germ line of an individual.What finding would suggest that the new mutation is dominant rather than recessive?

Accepted Answer

The answer of Assume that a new mutation occurs in...

Question 13

Conditional mutations are more likely to result from a mutation caused by which of the following alterations to the coding region of a gene?

Accepted Answer

Tautomeric shifts can cause base-pair mismatches during DNA replication, which can lead to frameshift or missense mutations that may create conditional alleles (i.e. mutations that affect gene expression under specific conditions). The other options may also cause mutations, but they are less likely to result in conditional alleles.

Question 14

Three major types of RNAs are mRNA,rRNA,and tRNA.For each of the conditions below predict the consequences in terms of the population of proteins being synthesized in a particular cell.What qualitative and quantitative changes,if any,are expected in the individual protein involved (if one is involved)and in the population of proteins produced in that cell?
a) A frameshift mutation in mRNA.The condition is heterozygous in the involved cell.
b) A deletion (homozygous)that removes approximately half of the rRNA genes.

Accepted Answer

The answer of Three major types of RNAs are mRNA,rRNA,and...

Question 15

Ultraviolet light causes pyrimidine dimers to form in DNA.Some individuals are genetically incapable of repairing some dimers at "normal" rates.Such individuals are likely to suffer from ________.

Accepted Answer

Xeroderma pigmentosum is a genetic disorder in which an individual's DNA repair mechanisms are impaired, particularly in repairing damage caused by UV light. This results in an increased susceptibility to skin cancers and other UV-induced skin damage.

Question 16

All insertion sequences (IS elements)contain two structural elements that are essential for their movement.What are these two elements?

Accepted Answer

All insertion sequences (IS elements) contain two structural elements that are essential for their movement. These two elements are transposase (the enzyme that mediates the transposition of the IS element) and inverted terminal repeats (the sequences that mark the ends of the IS element and that are recognized by the transposase). Therefore, choice A - transposase and inverted terminal repeats - is the correct answer. Choice B is incorrect because integrase is a term that refers to enzymes that catalyze site-specific recombination reactions, not transposition reactions; and pseudogenes are non-functional copies of genes. Choices C, D, and E are all incorrect because they refer to genes that have no direct connection with IS elements or transposition.

Question 17

In general,mutation rates in humans occur in the range of ________ (frequency)per gamete per generation.

Accepted Answer

The answer of In general,mutation rates in humans occur in...

Question 18

One type of mutation involves the replacement of a purine with a purine,while another causes the replacement of a pyrimidine with a purine or the reverse.What general terms are associated with these two mutational phenomena?

Accepted Answer

The answer of One type of mutation involves the replacement...

Question 19

List five general categories of mutation.

Accepted Answer

The answer of List five general categories of mutation....

Question 20

Mutations that arise in nature,from no particular artificial agent,are called ________.

Accepted Answer

Spontaneous mutations, as their name suggests, arise spontaneously in nature and are not induced by any particular artificial agent. They can occur due to errors in DNA replication or as a result of natural mutagens such as radiation or chemicals present in the environment. Oblique mutations, induced mutations, chromosomal aberrations, and cosmic mutations are not commonly used terms in genetics or biology.

Quiz 15: Gene Mutation,dna Repair,and Transposition