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The Dihybrid Cross. Two Pairs of Genes. Introduction Method Used: Punnett Square Principle: Complete Dominance Data: . Black fur is dominant to white fur. Curly fur is dominant to straight fur. Gene pairs: ( B-b ) ( C-c ) “ B †stands for black “ C †stands for curly
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The Dihybrid Cross Two Pairs of Genes
Introduction • Method Used: • Punnett Square • Principle: • Complete Dominance • Data: Black fur is dominant to white fur. Curly fur is dominant to straight fur. Gene pairs: ( B-b ) ( C-c ) “B” stands for black “C” stands for curly “b” stands for white ‘c’ stands for straight
4. List all the possible genotypes using B, b, C, c [from most to least dominant ] WE ARE GOING TO USE THE FOIL METHOD!!!!!! First…Outside…Inside…Last BC Bc bC bc Eggs BC Bc bC bc Sperm Gametes possible (”N”): BBCC BBCc BbCC BbCc BBcc Bbcc bbCC bbCc bbcc DESCRIBE EACH OF THESE INDIVIDUAL’S PHENOTYPE
A. Complete a Parent cross 1.) P cross 2.) 3.) BBCC x bbcc 4.) black,curly white, straight bc bc bc bc BC BC BC BC • Genotypes • BbCc : ------- • 16 : 0 BbCc BbCc BbCc BbCc BbCc BbCc BbCc BbCc • Phenotypes • Black,Curly:------- • 16 : 0 BbCc BbCc BbCc BbCc BbCc BbCc BbCc BbCc
F1 Cross • [cross between two individuals who are hybrid for two genes/traits] • (heterozygous black, heterozygous curly X heterozygous black, heterozygous curly) • [ BbCc ] x [ BbCc ]
BC Bc bC bc BC Bc bC bc 1.) F1 cross 2.) 3.) BbCc x BbCc 4.) Black, Curly Black, Curly BbCc BBCC BBCc BbCC BBCc BBcc BbCc Bbcc bbCC BbCC BbCc bbCc BbCc Bbcc bbCc bbcc
Calculate the genotype and phenotype ratios by counting: Genotype Ratio 1. BBCC 2. BBCc 3. BbCC 4. BbCc 5. BBcc 6. Bbcc 7. bbCC 8. bbCc 9. bbcc Phenotype Ratio 1. 2. 3. 4. 1 2 2 4 1 2 1 2 1 9 3 3 1 Black & Curly Black & Straight White & Curly White & Straight 9 : 3 : 3 : 1 1 : 2 : 2 : 4 : 1 : 2 : 1 : 2 : 1
