KA 3: variation and sexual reproduction: meiosis Flashcards
what is meiosis?
the division of the nucleus that results in the formation of haploid gametes from a diploid gametocyte
how do chromosomes typically appear in diploid cells?
as homologus pairs
what are homologus chromosomes?
chromosomes of the:
-same size
-same centromere position
-the same sequence of genes at the same loci.
describe meiosis I
MEIOSIS I
The chromosomes, which have replicatedprior to meiosis I, each consist of two genetically identical chromatids attached at the centromere
The chromosomes condense and the homologous chromosomes pair up
where does chiasmata form?
MEIOSIS I
at points of contact between the non-sister chromatids of a homologous pair and sections of DNA are exchanged
what are linked genes?
MEOISIS I
those on the same chromosome
what can crossing over result in?
MEOISIS I
new combinations of the alleles of these
genes
the crossing over of DNA is ____ and produces ________ recombinant chromosomes
MEOISIS I
-random
-genetically different
spindle fibres attach to the ________ and line up at the ________ of the spindle
MEOISIS I
- homologus pairs
- equator
describe the orientation of the pairs of homologus chromosomes at the equator
MEOISIS I
- random
what is independent assortment?
MEOISIS I
each pair of homologous chromosomes is positioned independently of the other pairs, irrespective of their maternal and paternal origin
the chromosomes of each ____ pair are ____ and move towards ________ poles
MEOISIS I
- homologus pair
- separated
- opposite
cytokinesis occurs and….
two daughter cells form
describe meiosis II
MEOISIS II
Each of the two cells produced in meiosis I
undergoes a further division during which the
sister chromatids of each chromosome are
separated
how many haploid cells are produced in meiosis II?
MEOISIS II
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