biol139-lecture3-2011

biol139-lecture3-2011 - Dihybrid Crosses Dihybrid Crosses...

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Unformatted text preview: Dihybrid Crosses Dihybrid Crosses BIOL 139 BIOL 139 found that factors (genes) for different traits assort independently independently of one another genes on different chromosomes behave independently in production of gametes Dihybrid Cross: Dihybrid Cross: simultaneous inheritance of two or more two or more unrelated traits How would these 2 pairs of alleles segregate? Would they segregate together or independently? Matings between individuals that differ in two unrelated traits (looks at alleles of 2 different genes) Two different alleles for a single gene that determines a single feature Monohybrid Cross Dihybrid Crosses: Dihybrid Crosses: S = smooth; s = wrinkled S = smooth; s = wrinkled Y = yellow; y = green Y = yellow; y = green Traits = pea colour/shape Alleles = yellow/green round/wrinkled A copy of EACH EACH trait would go to a gamete So far like monohybrid cross except two phenotypic traits followed not one But what about F2 when self F1 hybrids # 3 # 5 # 3 # 5 Creation of a dihybrid F1 S = smooth; s = wrinkled S = smooth; s = wrinkled Y = yellow; y = green Y = yellow; y = green Independent Assortment in a Dihybrid Cross Independent Assortment in a Dihybrid Cross this occurs through this occurs through independent assortment independent assortment alleles for pea colour / pea shape assort independently alleles for pea colour / pea shape assort independently during gamete formation during gamete formation i.e. pea colour (yellow or green) is in no way tied to pea shape i.e. pea colour (yellow or green) is in no way tied to pea shape (round or wrinkled) (round or wrinkled) 4 types of gametes produced in a 1:1:1:1 ratio 2 n gametes Dihybrid cross Dihybrid cross parentals parentals recombinants Would predict this from Mendels Law of Segregation Pea colour inherited in 3:1 ratio Pea shape inherited in 3:1 ratio Notice 9 genotypes Only 4 phenotypes Mendels law of independent assortment Mendels law of independent assortment...
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biol139-lecture3-2011 - Dihybrid Crosses Dihybrid Crosses...

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