DNA mutations Flashcards
define a gene mutation
a change in the DNA sequence of DNA in a gene
what are the three different types of mutations
substitution mutation
addition mutation
deletion mutation
what is substitution mutation
when the right base is changes for the wrong one e.g
ACTATC changes to AGTATC
what is addition mutation
when an extra base is added e.g
ACTATC changes to AACTATC
causes frame shift
what is deletion mutation
when a base is missed out e.g
ACTATC changes to ATATC
causes frame shift
how does substitution mutations affect proteins
genetic code is degenerate so codons can code for same amino acid so no change can happen
if one base is substituted then the rest will stay the same (no frame shift)
only time a difference will happen is if the mutation lead to an amino acid which had different bonds (hydrogen, ionic, disulphide)
or if it lead to a stop codon
how does addition or deletion affect proteins
frame shift happens
all amino acids after mutation are changed
position of start/stop codon is changed
shorter (truncated) protein formed
how do gene mutations affect proteins
base sequence changes on DNA
sequence of codons on mRNA is then changed
different amino acids can then be coded for
changed the sequence of amino acids in the polypeptide chain (primary structure)
different R groups on amino acid can cause different bonds and interactions during folding of tertiary structure
specific 3D shape (tertiary structure) of the protein will be different
protein cant carry out its function correctly
what are the two types of mutations
germ line mutation
somatic mutation
features of germ line mutations
occurs in the DNA of an ovary or testis that is dividing to form a sperm or an egg
mutations can be passed on to future generations
(e.g CF)
features of somatic mutations
occurs after contraception
not passed on to future individuals (mutation dies with individual)
(e.g cancer)
where is the CF gene located and what does it contain the code for
on chromosome 7
contains the code to make the CFTR protein
how do mutations affect the CFTR protein
CFTR protein is not made at all
CFTR protein is misfolded so does not function properly
CFTR protein is shortened
CFTR protein is made in smaller quantities
CFTR protein breaks down quickly after being made
