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Unformatted text preview: 4 daughter
are haploid ALL OF THEM ARE
GENETICALLY DIFFERENT! critical for growth critical for reproduction Three(events(unique(to(meiosis(occur(during(meiosis(I(
2. Homologs line up at metaphase plate
GENETIC VARIABILITY!!!!!!!!!! These differences are important because it is during these events that
genetic variation is generated in gametes --- crossing over and lining up of the homologs does this! How(do(we(account(for(gene;c(varia;on(in(oﬀspring(for(organisms(that(reproduce(sexually?( 1. Independent!Assortment!of!Chromosomes!
This happens in meiosis, the generation of gametes 2. Crossing!Over!
3. Random!Fer8liza8on! You never know which sperm is going to
fertilize which egg -- it's all random Each chromosome can line up independently of the other chromosomes During(Metaphase(I(–(homologs(line(up(on(the(metaphase(plate(
HOW they align is completely random!!!
can be like this...
Chromosome(2( …or like this Metaphase(I(
on right Metaphase(II(((((( Daughter(Cells( ! Combina8on(1((
This combo happens
to have them ALL paternal Combina8on(2((
Chromosome(2(maternal( This combo has paternal
and maternal chromosomes Can(quan;fy(the(number(of(possible(combina;ons=( Combina8on(4((
Chromosome(2(paternal( 2^n -- n is the # of chromosome pairs Hypothe;cal(Example:((Look!at!my!daughter’s!karyotype!and!focus!on!two!traits!(chin!shape!
Chromosome! ! R!and!r!are!alleles!for!
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- Spring '14