Presentation on theme: "Dihybrid Inheritance Dihybrid inheritance refers to the simultaneous inheritance of two characters."— Presentation transcript:
1 Dihybrid InheritanceDihybrid inheritance refers to the simultaneous inheritance of two characters
2 Mendel’s experimentMendel investigated the inheritance of seed shape (round v wrinkled) and seed colour (green v yellow) at the same time.From his monohybrid crosses he knew that round seeds were dominant to wrinkled seeds and yellow seeds were dominant to green seeds.He chose to cross plants that were pure breeding for both dominant features (round and yellow seeds) with plants that were pure breeding for both recessive features (wrinkled and green seeds)
3 ResultsParents plants with round x plants with wrinkled and yellow seeds and green seedsF1 offspring 100% plants with round and yellow seedsF1 intercross plants with round x plants with roundand yellow seeds and yellow seedsF2 offspring Total 556 seeds collected from F2 plantsRatioround and yellow seedsround and green seedswrinkled and yellow seedswrinkled and green seedsHowever, the ratio of dominant to recessive features is still 3:1
4 Explanation of Mendel’s results Let the allele for round seeds be R and the allele for wrinkled seeds be rLet the allele for yellow seeds be Y and the allele for green seeds be yParents Phenotype round x wrinkledyellow seeds green seedsGenotype RR YY rryyGametesF1 offspringRYRYryry
5 F1 intercrossParentsphenotype round, yellow seeds x round, yellow seedsgenotype Rr Yy Rr YyGametesRYRyrYryRYRyrYryWhat are the genotypes and phenotypes of the F2 offspring and in what ratio?
7 Allowing for statistical error, Mendel’s results were a reasonable approximation to the expected 9:3:3:1 ratioEach of a member of an allelic pair may combine randomly with either of another pairA test cross can be performed to check the possible genotypes of a plant producing round, yellow seeds (RRYY, RrYY, RrYy, RRYy) by crossing the plants with a homozygous recessive plant with wrinkled green seeds genotype rryyWhat phenotypes and genotypes would the offspring possess from the 4 crosses, and in what ratios?
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