Vassar College

Biology

1. Monohybrid Cross A. 2 Points a. Axial flowers are dominant to terminal flowers in pea plants. Set up a cross for a homozygous recessive parent to a heterozygous parent with these alleles. b. Show the P generation cross _________________. c. List the genotypes potentially present in F1 generation_________________. d. What percentage of the offspring are likely to have axial flowers/ terminal flowers? _______________________ B. 2 Points a. A mother carries the gene for methemoglobinemia and has a child with who also carries the gene for the disorder. Create a cross of the potential offspring genotype. b. Show the P generation cross _________________. c. List the genotypes potentially present in F1 generation_________________. d. What percentage of the offspring are likely to have methemoglobinemia? _______________________ C. Let’s reflect. 2 Points a. Explain how Punnett squares predict offspring allele outcome. b. Explain the Law of Segregation and how Punnett Square display this law.

2. Dihybrid Cross A. 2 points a. Two heterozygous, purple and tall pea plants are crossed. Look in your book/powerpoint to find the recessive traits. b. Which traits are dominant? Give the letters to use for those traits.______________________________ c. Which traits are recessive? Give the letters to use for those traits.______________________________ d. Show the P generation cross _____________________________________. e. Perform the cross of the P generation. f. What is the phenotypic ratio of the F1 generation?__________________________________. B. Explain the Law of Independent Assortment. (2 points) C.How is the Law of Independent Assortment exemplified in a dihybrid cross? (2 points)

3. Incomplete dominance (2 points) a. Explain how incomplete dominance works. b. Familial hypercholesterolemia is an example of an incomplete dominance trait. Provide a cross for a two heterozygous parents. c. P genotypes______________________ d. F1 genotypes __________________________________ e. How will the disorder present itself in each genotype of the offspring?

4. Pedigree Analysis A. (2 points) a. Determine the genotypes of the individuals in this pedigree. Use the letter E and e for the genotypes. b. Is this trait autosomal dominant, autosomal recessive, or X-linked? c. Explain your answer. B. (2 points) a. Determine the genotypes of the individuals marked in this pedigree. Use the letter A and a for the genotypes. b. Is this trait autosomal dominant, autosomal recessive, or X-linked? c. Explain your answer. C. (2 points) a. Create a pedigree for a family that has the Duchenne muscular dystrophy disorder within the family. The pedigree must have Roman numerals for generations, Arabic numerals for the individuals in each generation and those who are affected must be shaded. Carriers of the disorder should be half filled shaded. Tom is a young boy in the third generation of his family pedigree who has Duchenne muscular dystrophy. His maternal grandmother was a carrier of the disorder and she had 4 children, 2 boys and 2 girls. Tom’s mother and father did not have the disorder. b. Does Tom’s mother carry the allele? What is her genotype?

5. X-linked traits A. (2 points) a. Eye color in Drosophila melanogaster is an X-linked trait. Explain what X-linked means. b. Create a cross for a male D. melanogaster that has white eyes and a female that is heterozygous for red eyes. c. P generation____________________________________ d. F1 genotypes____________________________________ e. F1 phenotypes___________________________________ B. (2 points) A young boy that has adrenoleukodystrophy but parents without the disorder. a. What is the young boy’s genotype? b. What are his parents’ genotypes?

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