Mutations

Mutation

change in the nucleotide sequence of a gene or genome or a change in chromosome structure or organization

adaptation

a trait that promotes survival and reproduction of an organism in an environment

adaptation theory

Traits acquired during an organism’s lifetime can be passed to offspring.

mutation theory

mutations are random an then based on which traits are best the offspring will get them

germ line mutations

alter gametes and passed to the next generation

somatic mutations

occur in somatic cells so only affect the individual in which the mutation arises.

Result in a somatic mosaic of genotypes.

somatic mosaic

When an individual has two or more different genotypes in their somatic (body) cells.

substitution

base pair is replaced with another

deletion

One or more bases are removed from DNA.

insertion

One or more bases are added into DNA.

synonymous/silent mutation

Base pair substitution results in the same amino acid

Effect: No change in protein function

Nonsynonymous/missense mutation

Results in substitution of a different amino acid

Effect: Protein function may change

Nonsense mutation

Results in a stop codon (and shorter polypeptide)

Effect: Protein is truncated → usually nonfunctional

neutral mutation

Results in substitution of an amino acid with similar chemical properties (protein function is not altered).
Effect: Protein function not significantly affected

frameshift mutations

A mutation caused by insertion or deletion of bases that is not a multiple of 3.(shift the codon reading frame)

transition mutation

• A purine ↔ purine or pyrimidine ↔ pyrimidine change.

• Purines: A ↔ G

• Pyrimidines: C ↔ T

• Example: A → G or C → T

transversion mutation

• A purine ↔ pyrimidine change.

• Example: A → T or G → C

spontaneous mutations

Occur at any point of the cell cycle

induced mutations

Mutations caused by external factors

monogenic disease

Caused by a mutation in a single gene

polygenic disease

caused by mutations in multiple genes, often combined with environmental factors

consequences of base substitutions

silent , missense, nonsense, neutral