Exam 14: Gene Mutation, Dna Repair, and Transposition

Some mutagens cause genetic changes that can be "corrected" by reexposing cells to the same mutagen. Other mutagens do not behave in this way. Provide one example of each of these two types of agents and describe the mutational changes caused in DNA. Explain why some mutagens behave in one way, whereas others do not.

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

It has been found that a particular "+ -" combination of frameshift mutations in gene X gives a wild -type phenotype, whereas a "- +" combination gives a mutant phenotype, even though the sites of insertion/deletion are the same. How might these results be explained?

When X rays penetrate cells, electrons are ejected from atoms of molecules. Stable molecules can be transformed into which two types of hazardous materials?

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

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

List five general categories of mutation.

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.

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.

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

What is meant by the term photoreactivation repair?

Apurinic sites (AP sites) involve a spontaneous loss of a(n)________ in an intact double -helix DNA molecule.

The process of error correction of mismatched bases carried out by DNA polymerases is called _.

When treating an organism with a mutagen, although it is possible that homozygous mutations will occur, it is more likely that most new mutations will be heterozygous or hemizygous.

Of the two cell lines that can contain a mutation in an organism, somatic line and germ line, the latter is more consequential to subsequent generations.

Certain base analogs such as 5 -bromouracil cause mutations by chemically altering nitrogenous bases in nonreplicating DNA.

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?

Loss -of -function mutations eliminate the function of a gene product and may be dominant or recessive.

Considering the electromagnetic spectrum, identify likely mutagens from the following list: radio waves, microwaves, infrared, ultraviolet, X rays, gamma rays, cosmic rays.

Nutritional mutations can be described as _.