Chapter 13 Notes MEIOSIS

For eyebrowthicknessgene chinshape rround rpointed r

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Unformatted text preview: or! eyebrow!thickness!gene! ! Chin(shape( R(=(Round( r(=(pointed( R! Maternal! Chromosome! r! B(=(Bush( b(=(fine( What(is(an(allele?( ! Alternative version of a gene --- slight variations --- arise due to mutation! ( B! b! Eyebrow(( thickness( Ellie's meiosis was started before she was even born --- in women, it happens during GESTATION. Paternal! Chromosome! Ellie’s!Karyotype! ! *! This karyotype is ! from one of her somatic cells! ! When!Ellie’s!oocytes! complete!meiosis,!each! oocyte!will!be!haploid!and! gene8cally!unique! Maternal! Chromosome! Trait(=(Chin(Shape( R( R(=(Round( r(=(pointed( r( Interphase(I( R( r( R r( Each chromosome replicated Meiosis(I( Sister chromatids separate R r( R( r( Meiosis(II( R R( These are the resulting 4 possibilities! 50%(chance(paternal(chromosome( r( r( 50%(chance(maternal(chromosome( Trait(=(Eyebrow(Thickness( b( B( B(=(Bushy( b(=(fine( Interphase(I( b( b( b( B B( Meiosis(I( b( B B( Meiosis(II( b( b( Resulting 4 possibilities! 50%(chance(paternal(chromosome( B B( 50%(chance(maternal(chromosome( Key(Point:! The possibile combos of CHIN SHAPE and EYEBROW THICKNESS are completely independent of each other!!!!!!!!!!! Independent assortment If(you(combine(the(two(events:((what(are(the(possible(gamete(combina;ons?( ( R B Round!chin;!Bushy!eyebrows! R( b( Round chin, fine eyebrows r( B( Pointed!chin;!Bushy!eyebrows! r( b( Pointed chin, fine eyebrows In!this!example!we!considered!only!2!of!the!23!chromosomal!pairs!of!human!chromosomes! However,!!during!meiosis!I!all!23!pairs!of!chromosomes!align!on!the!metaphase!plate! ( How(many(possible(combina;ons(of(paternal(and(maternal(chromosomes(exist(in(each( gamete(that(Ellie(generates(in(her(life;me?( ( Number of possibile gamete combos is 2^n …. so 2^23 …. so that's 8.4 million! BUT THIS DOESNT EVEN INCLUDE CROSSING OVER!!!!! That can't be quantified though. Remember(that(crossing(over(also(generates(varia;on(in(gametes( Crossing!over!generates!recombinant!chromosomes!that!carry!genes!fr...
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