Monohybrid and Dihybrid Cross

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Problem Set – Monohybrid and Dihybrid Cross

1. Classical albinism results from a recessive allele. What is the expected offspring from a normally pigmented male with an albino father and an albino wife?

2. A pea plant with red flowers is test crossed and one half of the resulting progeny have red flowers, while the other half has white flowers. What is the genotype of the test crossed parent?

3. If we cross two pea plants each heterozygous for yellow seed color genes, what would be the expected phenotypic and genotypic ratio among the offspring?

4. In summer squash, white fruit color (W) is dominant over yellow fruit color (w) and disk-shaped fruit (D) is dominant over sphere-shaped fruit (d). If a squash plant true-breeding for white, disk-shaped fruit is crossed with a plant true-breeding for yellow, sphere-shaped fruit, what will the phenotypic and genotypic ratios be for: a. the F1 generation? b. the F2 generation?

5. In man, the ability to taste a substance, phenylthiocarbamide (PTC) is inherited as a dominant characteristic. To tasters, PTC is bitter; nontasters find it tasteless. Albinism, on the other hand, is inherited as a recessive trait. A couple, both tasters and normally pigmented married and their first child is an albino and a nontaster. a. What are the genotypes of the parents?

b. Give the genotypic and phenotypic ratio expected in their progeny. Use a Punnett square.

6. Determine the possible genotypes of the parent shown below by analyzing the phenotypes of their children. Assume that brown eyes (B) is dominant to blue (b) and that right handedness (R) is dominant to left handedness (r). Give expected genotypic ratios using the branching method.

|Parental Phenotypes |Phenotypic ratio in Progeny | | |Brown eyes; right-handed |Brown eyes; left |Blue...
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