Genetics Exam 4

What is a transition mutation?

a point mutation when a pyrimidine replaces a pyrimidine, or a purine replaces a purine.

What is a transversion mutation?

a point mutation when a purine and a pyrimidine are interchanged.

What is a missense mutation?

a point mutation where a base pair change results in a new triplet code for a different amino acid.

What is a nonsense mutation?

a point mutation where a base pair change results in a triplet code for a stop codon.

What is a silent mutation?

a point mutation where a base pair change results in a new triplet code that still codes for the same amino acid.

What is a frameshift mutation?

The loss or addition of a nucleotide that causes a shift to the reading frame, altering the entire amino acid sequence.

What is a forward mutation?

when a mutation takes an organism from its wild-type form to the mutant form.

What is a reverse mutation?

when a mutation causes an organism to reverse back to its wild-type form.

What is an intragenic suppressor mutation?

when a suppressor mutation occurs on the gene containing the mutation being repressed.

What is a suppressor mutation?

a mutation that suppresses the forward mutation, causing the wild-type phenotype to show while still possessing the original mutation.

What is an intergenic suppressor mutation?

when a suppressor mutation occurs in a gene other than the one bearing the original mutation it suppresses.

What is a lethal mutation?

a mutation that interrupts essential processes and results in death.

What is a lethal conditional mutation?

a mutation dependent on the organism’s environment, normally a temperature-sensitive mutation.

What is a neutral mutation?

a mutation that doesn’t affect an organism’s fitness

What are somatic mutations?

mutations that occur in any cell except germ cells and are not heritable

What are germ-line mutations?

mutations that occur in gametes and are heritable.

What are autosomal mutations?

mutations that occur within genes located on autosomes (any chromosome that is not a sex chromosome).

What is a spontaneous mutation?

a change in a nucleotide sequence that occurs naturally, from biological and chemical processes.

What are X- and Y-linked mutations?

mutations that occur within genes located on the X or Y chromosomes.

What is a tautomeric shift?

a change in the position of a hydrogen atom and a double bond on a nitrogenous base that causes a base pairing error (transition mutation) during DNA replication.

What are tautomers?

molecules with the same molecular formula but different connectivity. (EX: cytosine with the same molecular formula but one of the hydrogens on one of them is changed to a different position)

What can a tautomeric shift cause in base-pairing?

it can cause pyrimidines to be able to bind to other pyrimidines and purines to be able to bind to purines.

What is depurination? What can it lead to?

loss of purine leading to an apurinic site that can lead to a missing nucleotide pair.

What is deamination? What can it cause?

loss of an amino acid, the deamination of cytosine produces uracil. It can cause the DNA replication machinery to insert an adenine for the uracil, and if uncorrected, results in substitution of the base.

What is an induced mutation?

a mutation from influence of extraneous factors, either natural or artificial.

What is a mutagen?

a natural or artificial agent that induces mutations.

What is an oxidative reaction?

superoxide radicals, can be caused by exposure to high-energy radiation.

What are intercalating agents?

chemicals that wedge between DNA base pairs, distorting the 3D structure of the double helix, causing base-pair distortions and DNA unwinding.