Plants have multicellular haploid stage. Grasshopper chromosomes (color added)
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Transcript of Plants have multicellular haploid stage. Grasshopper chromosomes (color added)
Plants have multicellular haploid stage.
Grasshopper chromosomes (color added)
Simplification shows cell with diploid 2N=2.
Simplification shows cell with diploid 2N=2.
Simplification shows cell with diploid 2N=2.
In this example 2N=4; the “long” pair and the “short”.
In this example 2N=4; the “long” pair and the “short”.
Remember mitosis?
Cells produce more
identical cells.
Resembles Meiosis II,
when sister chromatids separate and cells divide.
Meiosis I isreduction divisionwhen diploid -->haploid.
Meiosis II is similarto mitosis; doublescell number.
Watch meiosis video,if possible.
How does meiosis generate variation?
Even without crossing over, meiosis generates variation.
2N combinations of maternal and paternal chromosomes.
Humans: 223 = 8.4 million
Recombination dramatically increases possibilities.In humans, about 50 chiasmata in meiosis I.Almost limitless variety of re-shuffling.
Recombinationscrambleschromosomes.
Figure from Hapmap.com
Black Oxford
Canadian StrawberryGoldrush
4 of the 79 apple varieties sold at Fedco seeds in Albion ME
Liberty
Sex is costly.
Abundance of trematode parasites
Pre
dom
inan
ce o
f se
x in
sn
ail
host
sSexuality important in escaping parasites.
Errors in meiosis