Unit 1 KA4 - Mutations Flashcards
what is a mutation?
a random change in the genome that can alter alleles, genes, gene expression or chromsosmes.
results in an altered protein being produced/no protein at all.
what is a single gene mutation and what types are there?
a change in the DNA nucleotide sequence of a single gene.
substitution (missense, nonsense, splice site mutation), insertion and deletion.
what are chromosome structure mutations and what types are there?
a change in the structure of one or more chromosomes.
deletion, duplication, insertion and translocation.
what is a substitution mutation and what types of substitution mutation can it lead to?
when one nucleotide is replaced with another nucleotide, leading to one amino acid coded for in the protein to be altered.
missense, nonsense and splice site mutation.
what is a missense substitution mutation and what does it result in?
the substitution of the nucleotide leads to an altered codon that codes for a different amino acid on the protein.
results in a non-functional protein.
e.g sickle cell anemia.
what is a nonsense substitution mutation and what does it result in?
the substitution of the nucleotide leads to a codon that normally codes for an amino acid coding for a premature stop codon instead.
results in protein synthesis stopping early and a shorter protein which is unable to function is formed.
what is a splice site mutation and what does it result in?
the substitution of the nucleotide leads to one or more of the introns being retained and or some exons not being included in the mature transcript.
results in the altered mature mRNA strand being translated into a different protein that doesn’t function properly.
what is a deletion/insertion mutation and what does it result in?
when a nucleotide is inserted/deleted.
results in a frameshift mutation, which alters every codon after the inserted/deleted nucleotide.
the mutated DNA codes for different amino acids after the inserted/deleted nucleotide, causing a major effect on the structure of the protein produced.
e.g. of frameshift insertion; TaySachs disease.
e.g of frameshift deletion; cystic fibrosis.
what is chromosome deletion and what does it result in?
when a section of a chromosome is removed.
the chromosome breaks in two places and the segment in between becomes detached.
the two ends join up, giving a shorter chromosome which lacks certain genes.
this has a drastic effect on the organism involved.
e.g Cri du Chat syndrome
what is chromosome duplication and what does it result in?
where a section of a chromosome is added from its homologous partner.
results in a set of genes being repeated.
e.g duplication of oncogenes is a common cause of cancer.
what is chromosome inversion and what does it result in??
the chromosome breaks in two places.
the segment between the two breaks turns around before joining up again.
this results in a section of a gene on the chromosome being revered.
therefore when a chromosome has undergone inversion and meets its normal, non-mutated matching partner at gamete formation, the two have to form a complicated loop in order to pair up.
this results in the formation of non-viable gametes.
what is chromosome translocation and what does it result in?
when a section of a chromosome breaks off and becomes attached to another chromosome which is not is homologous partner.
this results in problems during pairing of chromosomes at gamete formation, therefore non-viable gametes are formed.
e.ge Down’s syndrome.
Why does a frameshift mutation arise only if the number of nucleotides inserted or deleted is not a multiple of three?
If three nucleotides are involved, only a single amino acid will be affected.
