mutation and meiosis EQ Flashcards
what is a mutagenic agent
a factor that increases risk of mutations
what ways are genetic variation of a population increased
- crossing over in meiosis
- independent segregation in meiosis
- mutation
- random fusion of gametes
- produces new allele combinations
define gene mutation
gene mutation = change in the nucleotide sequence which results in formation of a new allele
how might a gene mutation have no effect on the individual
- genetic code is degenerate so Amino acid sequence may not change
- mutation is an intron so amino acid sequence no change
- does change amino acid but has no effect on tertiary structure
- new allele recessive so doesn’t influence phenotype
how might a gene mutation have a positive effect on the individual
- could result in a polypeptide which positively changes properties of the protein
- could result in increased reproductive success
differences between mitosis and meiosis
mitosis v meiosis:
- one division v 2 divisions
- 2 daughter cells produced v 4 daughter cells produced
- diploid to diploid v diploid to haploid
- separation of homologous chromosomes only in meiosis
- crossing over and independent segregation only in meiosis
what is structure of amino acid
NH2CHRCOOH
explain how chromosome number is halved in meiosis
homologous chromosomes pair
one of each pair goes to opposite poles to be part of each daughter cell
describe the process of crossing over and explain how it increases genetic diversity
homologous pairs of chromosomes associate
chiasmata forms
equal lengths of non sister chromatids are exchanged
produces new combination of alleles
what are the types of mutation
substitution
deletion
addition
chromosome mutations
explain substitution of bases
a nucleotide in DNA is replaced by a different nucleotide with a different base
could result in different amino acid being coded for
why could substitution not change protein coded for?
2 reasons
degenerate code- dna could still code for same amino acid
amino acid could change but tertiary structure remain the same
explain deletion of bases mutation
when a nucleotide is lost from normal sequence
polypeptide now unlikely to function properly as one deleted base causes whole code to shift to the left by one base
what is frame shift
when a nucleotide is added or deleted and the code shifts by one nucleotide
triplet now read completely differently
what are chromosome mutations
changes to structure or number of whole chromosomes
what are the 2 types of chromosome mutation
- changes in whole sets of chromosomes - organisms have 3 or more sets of chromosomes (polyploidy)
- changes in numbers of individual chromosomes- when homologous pairs fail to separate in meiosis
known as non-disjunction, usually results in one gamete having one more or less chromosomes
why are gametes haploid cells
otherwise in sexual reproduction, when gametes fuse the offspring would have double the amount of chromosomes
what happens in first meiotic division
homologous chromosomes pair up and chromatids wrap around each other, exchanging equivalent portions in crossing over
ends with one chromosome from each pair going to one daughter cell
what happens in the second meiotic division
chromatids move apart
four haploid cells form at end
what is recombination
the broken pieces from crossing over recombine with anther chromatid
