BIOL 243 - Theme 2D mutations

Changes in sequences and spontaneous mutations/inheritance of DNA

What are mutations?

Changes to nucleic acid sequence (DNA and RNA)

What is the word for mutations being inherited?

germline

What is the word for mutations being not inherited?

somatic

Mutation changes can be small (___) or large (____)

gene level or chromosomal

altered gene sequence can change _______ of the polypeptide resulting in…

can change the amino acid sequence, resulting in variation of phenotype

What can the effect on the phenotype be?

harmless/neutral, harmful/deleterous, beneficial/advantageous

What is primary force in evolution?

where nature selection favours beneficial mutations

what are germline mutations?

mutation originally occured in gametes and therefore becomes heritable

ex. sex-influenced trait - autosomal dominant trait that is dependent on sex (males express the trait in heterozygotes but females do not)

what are somatic mutations?

mutation occurs in a progenitor cell and all other daughter cells will express the mutation

cancer tumors are an example of somatic mutations

somatic cells are expressed as….

sectors (depends on time of mutation)

what are small-scale mutations?

changes to one of few base pairs

What is base substitution?

single nucleotide change as a result of point mutations

what is insertion?

one or more base pairs added in sequence during DNA replication usually resulting in frameshift mutation

what is deletion?

one or more base pairs skipped during DNA replication usually resulting in frameshift mutations

what are transitions?

purine to purine or pyrimidine to pyrimidine changes

what are transversions?

purine to pyrimidine or pyrimidine to purine chages

point mutations affect what?

amino acid sequence of polypeptides

what is missense mutation? (non synonymous)

codon change causes change in an amino acid

what is nonsense mutation (premature stop)

sense codon change into a stop codon (truncated polypeptide)

what is silent mutation (synonymous)?

codon change does not change the amino acid due to degeneracy of the genetic code

what is frameshift mutation?

insertion or deletion of a small number of base pairs that alter the reading frame

sickle cell anemia is a missense mutation effect?

single missense mutation in entire genome and a resulting amino acid change can have drastic effect on phenotype

missense mutation in the beta hemoglobin gene causes 6th amino acid change from glutamic acid to valine

red blood cells: deficiency in oxygen exchange, clog arteries, circulatory problems, higher risk of heart attack and stroke

large scale chromosomal mutations - what is deletion?

loss of genes

what is duplication/amplification?

increasing dosage of genes

what is translocation

interchange of genetic parts from nonhomologous chromosomes

what is inversion

reversing orientation of a segment of the chromosome

what are spontaneous mutations

naturally occuring mainly caused by replication errors (1 mutation/10¹⁰ bp of DNA replicated) and spontaneous lesions

what do spontaneous lesions include?

depurination and deamination of bases

what are induced mutations?

natural (environments) or artificial agent or mutagen that causes mutations at a rate much higher than spontaneous mutagens

what do mutagens do?

induce mutations by replacing a base, alter a base so it mispairs with another base or damage a base where it can no longer pair with any base

what are base analogs

mimic bases and incorporates into DNA (can cause mispairing during DNA replication)

e.g. 5-bromouracil;thymine analog that can pair with A or G

chemicals alter…

base strucutre to cause mispairing

what are alleles

one of different forms of gene (sequence variation) which cause different phenotypes

what are wild-type alleles

normal form of the gene found in nature or the standard laboratory strain of a model organism

what are loss of function alleles

mutations that reduce/eliminate gene function/expression

what are gain of function alleles

mutations that enhance gene function/expression

learning objectives

slay