Meiosis Flashcards
Definition of Diploid
Double the number of chromosomes as the haploid number. Normal number of chromosomes in cells.
Definition of haploid
Half the number of chromosomes as a diploid cell.
Definition of bivalent
2 homologous chromosomes that are paired up/connected.
definition of homologous chromosomes
The same chromosomes with different alleles.
definition of independent assortment
chromosomes/chromatids can end up at either end of the nucleus which causes variation
definition of crossing over
When two homologous chromosomes swap some alleles which causes variation.
definition of chiasma
point at which 2 homologous chromosomes cross over
definition of random fertilisation
Any sperm could fertilise the egg and any egg could have matured. This produces variation. Happens after meiosis.
what do mutation cause?
variation
describe crossing over
each half of a chromosome is the same (one half copied itself) homologous chromosomes then cross over at the chiasma. Alleles are then swapped.
when is crossing over most likely to happen?
on long chromosomes
why is variation good?
produce new characteristics that can help species survive. Deal with changes.
describe independent assortment
chromosomes can end up at either end of the nuclei so when it divides lots of different combinations are possible. During anaphase 1, chromosomes are separated so each daughter cell ends up with different combinations of maternal and paternal chromosomes.
describe random fertilisation
Any sperm can fertilise the egg. Any egg can mature. Happens after meiosis. each sperm/egg is different because of independent assortment.
compared to the start what happens to the number of chromosomes in meiosis?
it is half (haploid cells)