mutations Flashcards
(23 cards)
what happens when DNA is methylated
-DNA may wrap tighter around histone proteins
-this may affect gene expression (genes wont be expressed)
what is gene silencing
when a gene isnt transcribed
is DNA linear of circular in eukaryotic cells
linear
gene
sequence of bases that codes for a polypeptide or functional RNA
what does non-overlapping bases mean
each base in a sequence only used once to form a single codon
What is a degenerate mean in genetic code
more than one codon can code for a single amino acid
what does universal mean in genetic code
all organisms use same genetic code, same codons use same codons to code for same amino acids
what is a stop codon and which codons are they?
translation stops when these codons are read, UGA, UAA and UAG
What is a mutation in genetic code, what cells can they occur in
errors when DNA is being replicated, can occur in somatic cells and gametes
definition=a change in the arrangement of bases in a gene or structure of a chromosome
changes the arrangement of genes
how are mutations repaired and what happens if they arent repaired
faulty DNA can be repaired by specific enzymes
if not repaired new proteins being synthesised will be affected
what can happen if mutations in gametes aren’t repaired
mutations can be affected in all new cells in foetus that develops
whatre the types of mutation
neutral mutation: no change in proteins occur
production of superior protein:
reproductive advantage
production of inferior or no protein: fatal or disease causing
what is a substitution mutation
change in one base
what does a deletion or insertion result in
a frameshift
alters all amino acids downstream of the mutation, non-functional protein produced
what is a nonsense mutation
introduction of a stop codon in the middle of a base sequence, no protein produced
what is a missense mutation
change of only one amino acid, unlikely to affect overall protein
what is a silent mutation
no amino acids affected due to degenerate nature of genetic code
what type of mutation is the most common mutation that causes CF
deletion so frameshift mutation
3 bases coding for phenylalanine
deleted
its removal leads to a change in structure of the CFTR protein
difference between a base and a nucleotide
nucleotide contains one base
a ribose or deoxyribose sugar
and a phosphate group
difference in effects of deletion and substitution of bases
-substitution may lead to the same amino acid being coded for which wont change the sequence of amino acids in the polypeptide produced
-substitution may only affect one amino acid in the polypeptide sequence which is unlikely to produce a different protein overall
-deletion may affect the sequence in the polypeptide chain forming an entirely new protein
-may lead to a frameshift resulting in a non functional protein being produced as all following codons after the mutation will be affected
if one nucleotide deleted, sequence of mrna nucleotides after that point will be in a different position (frameshift=each nucleotide will move up one) entire sequence will be changed so no or non-functional protein will be produced
also more likely with deletion of nucleotides that a stop codon will be introduced in a different position too early, meaning translation will be finished before the polypeptide chain is complete
substitution may not affect position of other amino acids , wont lead to a frameshift, sequence of polypeptide chain may not be altered. only one amino acid different or no different amino acid due to degenerate nature of genetic code- substitution may code for the same amino acid
whatre the 2 types of frameshift mutation
deletion or insertion of a base
both affect all the following codons as code is non overlapping so bases that wouldve been read in one codon if no mutation occurred are now read in a different codon, different triplet code so different amino acids coded for, different or no protein will be produced
how many polypeptides does one gene usually code for
1
