What phenotypic ratio is expected from this cross | Homework Helpers

Genetics with Drosophila melanogaster lab Assignment

Pre-Lab Assignment

Q1. Several weeks ago, a homozygous wild-type (winged) strain of flies was crossed with a homozygous apterous (wingless) strain of flies. Using standard genetic notation, this cross can be represented as ap⁺/ap⁺ × ap/ ap. The F₁ progeny of this cross were all winged. Based on the results of this cross, determine the dominant and recessive relationship of the ap⁺ and ap alleles.

A. Which allele is dominant, ap⁺ or ap?

B. What is the genotype of the F₁ flies?

Q2. Next, the F₁ progeny were crossed with one another to generate the F₂ generation. During the laboratory period, you will be given a flask containing the F₂ progeny of this cross. You will be counting the number of offspring in each category during the lab. To analyze your data, you will need to know the expected genotypic and phenotypic ratios for the F₂ generation. Use the Punnett Square provided below to help you to predict these ratios.

Report the genotypic and phenotypic ratios you predict for this cross based on the Punnett Square you completed.

A. What is the genotypic ratio that is expected from this cross?

B. What is the phenotypic ratio that is expected from this cross?

Q3. In the second cross you analyze, you will consider the segregation of the alleles of two different genes, apterous and sepia. The allele symbols for the apterous gene are ap+ (wild-type, winged) and ap (wingless, or apterous).

The allele symbols for the sepia gene are se+ (wild-type, red eyes) and se (sepia eyes). Several weeks ago, a homozygous wingless strain with red eyes was crossed with a homozygous winged strain with sepia eyes. The F₁ progeny of this cross were all winged and had red eyes. Use standard genetic notation to represent this cross. Include the genotypes of both the parents and the F₁ offspring.

Q4. The F₁ flies from this cross were crossed with one another to generate the F₂ generation. During the laboratory period, you will be given a vial containing the F₂ progeny of this cross. You will be counting the number of offspring in each category during the lab. To analyze your data, you will need to know the expected genotypic and phenotypic ratios for the F₂ generation. Use the Punnett Square provided below to help you to predict these ratios.

Report your predicted results of the dihybrid cross based on the information you included in the Punnett Square.

A. What types of gametes will be produced by the F₁ flies?

B. What phenotypic ratio is expected from this cross?

Attachment:- Biology Lab.rar