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r(=(pointed( R! Maternal!
Chromosome! r! B(=(Bush(
! 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!
*! This karyotype is
! from one of her
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
4 possibilities! 50%(chance(paternal(chromosome( r( r( 50%(chance(maternal(chromosome( Trait(=(Eyebrow(Thickness(
b( B( B(=(Bushy(
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!
( 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(
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- Spring '14