meiosis Flashcards
what is a mutation
change in dna base sequence
what can mutations be
spontaneous
or
induced e.g radiation chemicals
what is a substitution
causes a single base to change may not change amino acid sequence due to degenerate dna
what is an intertion or deletion
extra base is added in or a based is removed these cause a frameshift and will cause a change in the amino acid sequence
where does meiosis take place
ovaries and testes
what kind of cells are gametes
haploid so only have half number of usual chromosomes
describe meiosis
DNA is replicated in interphase before meiosis begins
In the first division there is a separation of homologous chromosomes, halving the chromosome number
In the second division there is separation of the sister chromatids
This produced four genetically different daughter cells
how does meiosis produce genetically different cells
-crossing over
-independent segregation
-random fusion of gametes
what is crossing over
crossing over in meiosis 1 is where chromadids break off and rejoin with another chromosome so alleles are swapped around causing new combinations
what is independent segregation
this is the production of different allele combinations in daughter cells due to the random alignment of homologous pairs along the equator
the combinations of different chromosomes in each daughter cell increases genetic variation
what is non disjunctions
During meiosis, homologous chromosomes fail to separate (meiosis 1) or sister chromatids fail to separate, meiosis 2,.
This results in gametes with too many or too few chromosomes.
It can lead to significant implications for the offspring such as genetic disorders.
what are differences between mitosis and meiosis
-asexual reproduction is used for mitosis and sexual reproduction is for meiosis
-meiosis produces 4 daughter cells mitosis only 2
-mitosis produces genetically identical cells meiosis produces genetically different cells
-mitosis produces diploid cells meiosis produces haploid cells
