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Biology LibreTexts

4.S: Mutation and Variation (Summary)

  • When a variation in DNA sequence originated recently, and is rare in a population, we call that change a mutation.
  • When variations in DNA sequence co-exist in a population, and neither one can be meaningfully defined as wild-type, we call the variations polymorphisms.
  • Mutations may either occur spontaneously, or may be induced by exposure to mutagens.
  • Mutations may result in either substitutions, deletions, or insertions.
  • Mutation usually causes either a partial or complete loss of function, but sometimes results in a gain of function,including new functions.
  • Spontaneous mutations arise from many sources including natural errors in DNA replication, usually associated with base mispairing, or else insertion deletion especially within repetitive sequences.
  • Induced mutations result from mispairing, DNA damage, or sequence interruptions caused by chemical, biological, or physical mutagens.
  • By randomly inducing mutations, then screening for a specific phenotype, it is possible to identify genes associated with specific biological pathways.
  • Transposable elements are dynamic, abundant components of eukaryotic genomes and important forces in evolution.
  • Transposable elements are dynamic, abundant components of eukaryotic genomes and important forces in evolution.
  • The efficiency of mutant screening is limited by silent mutations, redundancy, and embyronic lethality.
  • Mutation of different genes can produce a similar phenotype.
  • Complementation testing determines whether two mutants are the result of mutation of the same gene (allelic mutations), or if each mutant is caused by mutation of a different gene (non-allelic mutations).

Key Terms

mutation

mutant

polymorphism

insertion

deletion

substitution

mutagen

DNA replication error

Strand slippage

biological mutagen

chemical mutagen

physical mutagen

mispairing

loop

SSR

insertional mutagen

Class I, Class II

transposon

retrotransposon

reverse transcriptase

transposase

non-autonomous

autonomous

SINE, LINE, Alu

P-element

T-DNA

copy-and-paste

cut-and-paste

alkylation agent

EMS

intercalating agent

benzopyrene

carcinogenic

ethidium bromide

thymine dimer

mutant screen

 

loss-of-function

gain-of-function

amorph

null

hypomorph

hypermorph

neopmorph

dominant negative

somatic cells

germline cells

 

silent mutation

inter-genic region

redundancy

essential gene

recessive lethal allele

complementation testing

allelic / non-allelic

cM0, M1, M2

redundancy

lethality

allelic

non-allelic

complementation group

CFTR

Cystic Fibrosis (CF)

DF508(PHE508DEL)

Kalydeco

 

 

 

 

 

 

 

Contributors