19.1: effect of mutations on gene structure and function

mutation

mutation

permanent change of DNA that is heritable

what do mutations do for the gene pool

create allelic variation in the gene pool

do mutations always affect phenotype

no

are mutations always good

no sometimes they are detrimental to the organism and sometimes they have no effect on the organism

point mutations

change of a single nucleotide

what are the different ways a point mutation happens

addition of a base, deletion of a base, base substitution

transition

pyrimidine switched for another pyrimidine, purine for another purine

transversion

pyrimidine switched for purine, purine for pyrimidine

what type of point mutation is more common

transition because polymerase wants the structure to be as close as possible to what its supposed to be

can addition and deletion of multiple bases happen

yes

what effect do base substitution, additions and deletions have on protein function

can have very little if one amino acid is changed, but if the reading frame is changed the entire protein is altered and it can have a huge effect on protein function

silent mutations

do NOT alter amino acid sequence; because genetic code is degenerate

missense mutations

result in change in amino acid

what type of amino acid is considered neutral

nonpolar amino acids

what does a neutral amino acid mean

it does not affect protein function

what type of amino acid change is more likely to change protein function

change from a polar to nonpolar molecule, protein might not fold correctly, be in wrong conformation

in the case of a point mutation where an amino acid is changed from glutamic acid to valine why does it affect cell structure

because glutamic acid is a polar amino acid and valine is a nonpolar amino acid

nonsense mutations

codon for amino acid changed to a stop codon; causes translation to stop and can greatly affect protein structure depending on where the stop codon is in relation to the end of the chain

frameshift mutations

shift reading frame, different amino acid sequence altogether

wild type

prevalent genotype, phenotype in natural population

mutant allele

rare mutation within a population

reversion mutation/ suppressor mutation

a mutation that changes a mutant allele back to wild-type, 2nd site mutations that affect expression of the first mutation

deleterious mutation

decreases chances of survival/ reproduction

lethal mutation

results in death of an organism; mutations on important genes

beneficial mutation

enhances survival and reproduction of an organism

conditional mutation

phenotype only affected under certain conditions

intragenic suppressor mutation

the 2nd mutation site within the same gene as the first

intergenic suppressor mutation

2nd mutation site in a different gene than the first

intergenic suppressor redundant function

1st mutation inhibits function, 2nd mutation alters protein to carry out function, loss of function mutation compensated for by gain-of-function mutation

intergenic suppressor common pathway

proteins function in the same pathway, 1st mutation causes defect in enzyme 1 that slows catalysis, 2nd mutation alters enzyme 2 to increase function

intergenic suppressor multimeric protein

each subunit of multimeric protein encoded by different gene, 1st mutation occurs in gene for one subunit that inhibits function, 2nd mutation in gene for different subunit restores function

intergenic suppressor transcription factor

1st mutation causes loss of function, 2nd mutation in gene for transcription activates expression of another gene compensating for the loss of function

germ line cells

give rise to gametes

where do germ-line mutations occur

in sperm or egg or during gametogenesis and all cells of offspring will have this mutation

somatic cells

all cells of the body except germ line cells

somatic mutations

may occur at anytime during development, mutation passed to daughter cells NOT offspring