Gene mutation

what is mutation

any change to the quantity or base sequence of the DNA of an organism

when can mutation be inherited

when mutations occur during the formation of gametes

what is gene mutation

any change to one or more nucleotide bases or a change in the sequence of the bases

what can any changes to one or more bases in the DNA triplets result in

the change of the amino acid sequence

What are the 3 types of gene mutation

substitution, addition/insertion, deletion

what is (a single base) substitution

the replacement of a single-base nucleotide with another nucleotide

what are the 3 types of substitution?

nonsense, missense, silent

what is a nonsense mutation (substitution)

code for a stop-codon, which truncates the protein

what is a missense mutation

codes for a different amino acid

what is a silent mutation

codes for the same amino acid

what is addition/insertion?

addition of one or more nucleotide base pairs into a dna sequence

what is deletion

nucleotide is removed from the replicated dna strand

what is a frame shift

when a base/multiple bases are inserted, removed or duplicated into the genome which alters number of bases in the DNA sequence. all triplet codes downstream from the mutation shift are affected

what happens if gene mutation occurs in an intron

polypeptide is not affected as the introns are cut out before translation

what happens if 3,6 etc (multiples of 3) bases are inserted?

reading frame will not be shifted but more amino acids will be added into the chain

what are chromosome mutations

changes in the structure or number of whole chromosomes

2 types of chromosome mutations

changes in whole sets of chromosomes, changes in number of individual chromosomes

explain the chromosome mutation ‘changes in whole sets of chromosomes;

occurs when organisms have three or more sets of chromosomes rather than the usual two. polyploidy, occurs mostly in plants

explain the chromosome mutation ‘changes in the number of original chromosomes’

non-disjunction. when individual homologous pairs of chromosomes fail to separate during meiosis. results in monosomy (one chromosome less e.g. turner sndrome) or trisomy (one chromosome too many e.g. down syndrome)

what is turners syndrome

the affected individual is monosomic for the X chromosome

what is down syndrome

trisomy of chromosome 21