GENETICS NOTES - dihybrid cross
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GENETICS NOTES: DIHYBRID CROSS GENETICS NOTES: DIHYBRID CROSS Definition: 2 traits; different (hybrid or heterozygous) for each. Ex. Trait 1 = seed shape: R= Round , r = wrinkled Trait 2 = seed color: Y = Yellow, y = green Definition: 2 traits; different (hybrid or heterozygous) for each. Ex. Trait 1 = seed shape: R= Round , r = wrinkled Trait 2 = seed color: Y = Yellow, y = green What is the P generation _________ x _________ What is the P generation _________ x _________ F1 Generation: RrYy x RrYy a) Each parent gives one allele for each trait to offspring. So, each gamete should have one “R” and one “Y”. b) “FOIL” to determine possible gametes. First = Outer = Inner = Last = c) Since both parents have same genotypes (RrYy) the possible alleles for each will be the same. d) Determine # of squares in Punnett Square (42 = 16) e) Draw Punnett Square RY RY RRYY Ry RRYy rY ry RrYY RrYy Ry RRYy RRyy RrYy rY RrYY RrYy ry RrYy Rryy F1 Generation: RrYy x RrYy a) Each parent gives one allele for each trait to offspring. So, each gamete should have one “R” and one “Y”. b) “FOIL” to determine possible gametes. First = Outer = Inner = Last = c) Since both parents have same genotypes (RrYy) the possible alleles for each will be the same. d) Determine # of squares in Punnett Square (42 = 16) e) Draw Punnett Square RY Ry rY ry RY RRYY RRYy RrYY RrYy Rryy Ry RRYy RRyy RrYy Rryy rrYY rrYy rY RrYY RrYy rrYY rrYy rrYy rryy ry RrYy Rryy rrYy rryy f) Add gametes to outside of Punnett Square g) Conduct cross; following down and across fill in possible offspring. h) Determine the different phenotypes. Round + Yellow =9 Round + green =3 wrinkled+ Yellow = 3 wrinkled + green = 1 i) How many different types of genotypes are possible for this cross? List them. 9 different genotypes for this cross. f) Add gametes to outside of Punnett Square g) Conduct cross; following down and across fill in possible offspring. h) Determine the different phenotypes. Round + Yellow =9 Round + green =3 wrinkled+ Yellow = 3 wrinkled + green = 1 i) How many different types of genotypes are possible for this cross? List them. 9 different genotypes for this cross.
