meoisis Flashcards
(12 cards)
which process of cell division produces genetically identical cells?
mitosis
which process of cell division produces genetically different cells?
meiosis
how many nuclear divisions does meiosis involve?
two
how many haploid daughter cells does meiois produce?
four
what is the difference between a haploid and diploid cell?
- haploid cell has one set of chromosomes
- diploid cell has two sets of chromosomes
diploid cell example:
- muscle cells
- blood cells
- skin cells
- nerve cells
haploid cell example:
- sperm cell + egg cell
- pollen in plants
what are the two mechanisms in meiosis which introduce variation?
-** Independent segregation of homologous chromosomes
- crossing over **between homologous chromosomes
both occur during meiosis 1!!!
(first round of division)
what is a homogulous pair of chromosomes?
- two chromosomes
- with exactly the same genes
- but different alleles
what is independant segregation?
- homologous pairs of chromosomes line up opposite each other at equator of cell
- random which side the paternal and maternal chromosomes lie
- one of each homogolous pair ends up in daughter cell
what does independant segregation create?
- large number of possible combinations of chromosomes in daughter cells
how do we calculate the number of possible combinations for chromosomes in meiois
2^n
where n= number of homogulous pairs
e.g. humans have 23 homogulous pairs
so 2^23 = 8,388,608 combinations in humans
what is crossing over?
- chromatids become twisted around each other
- tension causes pairs of chromatids to break
- broken parts recombine with another chromatid
- results in a new combination of alleles
compare mitosis and meiosis
meiosis:
- two nuclear divisions
- haploid cell (one set of chromosomes)
- introduces genetic variation
mitosis
- one nuclear divison
- diploid cells (two sets of chromosomes)
- creates genetically identical cells
