meiosis Flashcards
what are the 2 types of mutation
gene mutation
chromosme mutation
what are gene mutations
change in the sequence of bases on the DNA
ultimately changes AA code and protein
what are chromosome mutations
a change in the no of chromosomes or change in the overall structure of a chromosome
what are spontaneous gene mutations
random mistakes occurring in DNA replication
no particular cause and occur with low frequency
how can the rate of mutation be increased
by exposure to mutagenic agents
radiations- x-rays and UV light
some chemicals eg benzpyrene in tobacco smoke which damages base cystosine
infectious agents eg HPV
what are the 4 types of gene mutation
-addition
-deletion
-substitution
-inversion
what is an addition mutation
one or more bases are added
thus frameshift and shifts reading frame-diff protein
what is a deletion mutation
one or more bases are deleted from sequence
thus frameshift and shift in reading frame - diff protein
what are substituition mutations
one nucleotide base or codon is exchanged for another so only triplet is affected
non-frameshift as only affect on triplet coden so not reading frame
what are inversion mutations
a base pr a sequence of bases is reversed
non-frameshift
what are the consequences of gene mutations
silent mutations - no effect
due to the removal of introns / mini satellite
code is degenerate - one codon for multiple
mis-sense- leads to formation of altered proteins
sequence of bases changed = altered mRNA
altered mRNA can be translated to diff AA seq
may then form protein w altered tertiary struct
causes affect on function
can be beneficial - advantageous characteristics
or harmful as non-functional
nonsense
codon changed to STOP codon then translation is ended prematurely and will be non-functional
has a serious affect on cell
what are the chromosome mutations
deletion- segment of chromosome is lost - vital genes could be lost
translocation- segment transferred onto another
duplication- section of chromo is transferred onto its homologous counterpart- so now had 2
inversion- large segment of chromo is now reversed
how are the changes in chromo number referred as
small-scale losses or small-scale gains
what is gaining a chromo called
trisomy eg downs syndrome
what is losing a chromo called
monosomy
what is having a complete extra set of chrome called
polyploidy - only plants
how many divisions are in meiosis
2