relationship between genes, proteins and phenotypes

gene mutation

change in the structure of a DNA molecules producing a different allele

chromosome mutation

changes in the structure of whole chromosomes in a cell

mutagens

increase the chance of mutations…random and environmental factors

types of gene mutations

base substitution, addition and deletion

silent consequences

same amino acid produced

missense

different amino acid produced with no apparent effect

nonsense

introduce a stop triplet

frame shift

protein that is made becomes totally useless

HBB gene, haemoglobin and sickle cell anaemia

substitution occurs in B-globin resulting in change from glutamic acid to valine…haemoglobin becomes less soluble, fibres inside blood form, sickle shape and blood cells become stuck in capillaries

TYR gene, tyrosinase and albinism

autosomal recessive mutation…results in the absence of tyrosinase and presence of ineffective tyrosinase…melanin is missing from eyes, skin and hair; poor vision and jerky eyes resulting in avoiding light

tyrosinase pathway

tyrosine to DOPA to dopaquinone to melanin pigment

HTT gene, hintingtin and Huntington’s disease

mutation inherited as a dominant allele…resulting in neurological disorder with involuntary movements and progressive mental deterioration…the more stutters present, the earlier onset age occurs

non sufferers of HD

few repeats of CAG bases

sufferers

large numbers or stutters of CAG bases

F8 gene, factor VIII and haemophilia

sex linked mutation…factor VII is a blood clotting agent