1. Simulate Mendel’s experiments using a dihybrid cross, in which he defined the law of independent assortment. Use two physical traits in dragons – Color and body covering. The color locus has two alleles: Green (G) which is dominant, and yellow (g) which is recessive. The skin locus also has two alleles: Scaled (S) is dominant to scaleless (s).
a. What types of dragons would you use as the parental generation? b. What would be the phenotype(s) of the F1 generation dragons? c. Write out the genotypes of the F1 dragons that will be used to breed and give rise to the F2 generation.
d. What gametes can be produced by the F1’s?
e. What will be the expected phenotypic ratios among the F2 offspring?
2. In horses, black color is dominant (B) and chestnut is recessive (b). Trotting (T) is dominant to pacing (t). A homozygous black pacer is mated to a homozygous chestnut trotter. a. How many loci are being studied?
b. What are the genotype(s) and phenotype(s) of the offspring of this initial cross?
Above you made F1 dihybrids. Now we can mate any of those F1’s together, resulting in an F2 generation.
c. Write out the genotypes of two F1’s you will breed together. d. What gametes can each of these F1’s produce?
e. What are the phenotype ratios among the resulting F2 offspring? f. What is the expected outcome of a cross of Bbtt x bbTt?
g. Is the cross described in “f” a dihybrid cross?
3. Cattle heterozygous for Red coat (R) and white coat (r) are roan (Rr); a type of gene action called incomplete dominance.
a. If two roan cattle are mated, what are the phenotype ratios of offspring?
(Remember that In cattle, Polled (hornless) (P) is dominant over horned (p)).b. If a polled (Pp) white cow is mated to a horned roan bull, what are the offspring phenotype ratios?
c. What are the expected ratios of a polled (Pp) roan cow and a horned white bull?
4. In humans, ABO blood groups (blood type) are determined by a...
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