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Embed code for: 15 meiosis
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Notes starting 4/13-17 for the week
Sex Cell Division
Meiosis occurs in sexual reproduction when a diploid germ cell produces four haploid daughter cells that can mature to become gametes (sperm or egg).
Goal: reduce genetic material by half
Why?n (mom) + n (dad) = 2n (offspring)
Meiosis: cell division in two parts
Result: one copy of each chromosome in a gamete.
Meiosis I : the reduction division
Crossing over occurs.
Nuclear envelope fragments.
Homologous pairs align
along the equator of the cell.
Chromosomes separate and
move to opposite poles.
Sister chromatids remain
Attached at their centromeres.
Nuclear envelopes reassemble.
Cytokinesis divides cell into two.
Sister chromatids carry
Meiosis II produces gametes with
one copy of each chromosome and thus one copy of each gene.
Meiosis II : the equational division
along equator of cell.
Sister chromatids separate
and move to opposite poles.
Nuclear envelope assembles.
Results of meiosis
Four haploid cells
One copy of each chromosome
“Putting It All Together” - Fertilization
What Meiosis is About
Meiosis allows the creation of unique individuals
through sexual reproduction.
Number of divisions
Number of daughter cells
Same as parent
Half of parent
At sexual maturity
Growth and repair
Occurs in somatic (body) cells
Occurs only in gonads (sex organs: ovary/testes)
Produces cells for repair,
maintenance, growth, asexual reproduction
Only produces gametes (sex cells: egg/sperm)
Results in identical diploid (2n) daughter cells
Reduction division results in haploid (n) cells