Genetics Exam 5

Anticipation

a phenomenon where genetic disorders become more severe or have an earlier onset in successive generations due to expanding nucleotide repeats

Base Excision Repair (BER)

A DNA repair mechanism where glycosylases remove damaged bases; the site is then cut and filled in with correct nucleotides.

Base Substitution (point mutation)

A mutation that replaces one nucleotide with another; includes transitions and transversions.

Conservative mutation

A type of missense mutation where the substituted amino acid has similar chemical properties to the original.

Coding region mutation

A mutation that occurs in a gene’s coding sequence and may alter the protein's amino acid sequence.

depurination

Loss of a purine base from DNA, creating an apurinic site that may result in substitution mutations during replication.

deamination

The removal of an amino group from a base, such as 5-methylcytosine, often resulting in C→T transitions.

endogenous mutation (spontaneous)

Mutations that occur naturally without external influence, e.g., errors in replication or spontaneous chemical changes.

Enhancer mutation

A change in regulatory DNA that can affect gene transcription levels.

forward mutation

A change from the wild-type allele to a mutant form (e.g., A⁺ → A⁻)

frameshift mutation

Insertion or deletion not in multiples of three, altering the reading frame of translation.

Gain of Function mutation

Mutation that results in a new or enhanced gene function, often with dominant inheritance.

Hypermorphic mutation

A GOF mutation that causes overexpression or a more efficient gene product.

hypomorphic mutation

A LOF mutation that results in reduced gene function.

in-frame mutation

An insertion/deletion in multiples of three, preserving the reading frame.

indel

Short insertion or deletion of nucleotides in the DNA sequence.

intragenic suppressor mutation

A second mutation within the same gene that compensates for the effect of a prior mutation.

intergenic suppressor mutation

A second mutation in a different gene that restores function lost by the first mutation.

Loos of Function mutation

A mutation causing reduced or abolished activity of a gene product, often recessive.

mismatch repair

A system for correcting base mispairings that arise during DNA replication.

missense mutation

A base substitution that changes one amino acid in the protein sequence.

mutation

A heritable change in the nucleotide sequence of DNA

Neomorphic mutation

A GOF mutation causing a gene to be expressed at the wrong time or in the wrong place.

nonsense mutation

A base substitution that changes a codon to a stop codon, truncating the protein.This results in a prematurely shortened protein that may lose its function.

nonconservative mutation

A missense mutation where the new amino acid has different chemical properties, often affecting protein function.

noncoding region mutation

A mutation outside the coding sequence that may impact regulation, splicing, or mRNA stability.

Nonhomologous end joining (NHEJ)

An error-prone DNA repair mechanism that joins broken DNA ends without a template.

promoter mutation

A change in the promoter region that can alter transcription levels.

reverse mutation (revertant)

A mutation that restores the original wild-type sequence or phenotype.

silent mutation

A base substitution that does not alter the amino acid due to codon degeneracy.

somatic mutation

A mutation in body cells that is not passed to offspring.

spontaneous mutation

A naturally occurring mutation, such as replication errors or chemical changes.

strand slippage

A replication error where DNA polymerase slips, causing indels or repeat expansions.

suppressor mutation

A secondary mutation that compensates for the effect of a primary mutation.

transition

A base substitution between purines (A↔G) or between pyrimidines (C↔T).

transversion

A base substitution between a purine and a pyrimidine (A/G ↔ C/T)

triplet repeat disorder

A disorder caused by expansions of three-nucleotide sequences (e.g., CAG in Huntington's).

trinucleotide repeat expansion

An increase in the number of three-nucleotide repeats, often causing genetic disorders.