Cross #1: P: F1 Fs Homozygous scarlet-eyed males Homozygous brown-eyed females X 1072 Wild-type (red-eyed) males and females F1 males x F1 females 2684 wild-type males and females 891 scarlet-eyed males and females 887 brown-eyed males and females 298 white-eyed males and females

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You are conducting independent research for your Honors Thesis in a Drosophila research lab.  One of the graduate student researchers has provided you with two mutant strains of Drosophila.  One has scarlet eyes, and the other has brown eyes.  You cross homozygous scarlet-eyed male Drosophila with female flies homozygous for the brown-eye color allele, and all of the male and female F1 flies have wild-type eyes.  Crosses involving F1 males x F1 females yield the results shown below. You know the traits involved are autosomal, and that reciprocal parental crosses produce similar results.  

a) What is the phenotypic ration observed among the offspring in the F2 generation?

b) How many pairs of genes are involved in determining these traits? Please explain in detail.

c) Please EXPLAIN the genetic basis for the pattern of inheritance illustrated in this cross. Be sure to mention the alleles involved.

### Genetic Cross Experiment: Eye Color in Drosophila

#### Cross #1:

**Parental Generation (P):**
- Homozygous scarlet-eyed males (ss) 
- Homozygous brown-eyed females (bb) 

**First Filial Generation (F₁):**
- Result: 1072 Wild-type (red-eyed) males and females

**Second Filial Generation (F₂):**
- Cross: F₁ males x F₁ females
- Result:
  - 2684 wild-type males and females
  - 891 scarlet-eyed males and females
  - 887 brown-eyed males and females
  - 298 white-eyed males and females

#### Explanation:

In this genetic cross experiment, the purpose was to study the inheritance pattern of eye color in Drosophila melanogaster (fruit flies). 

1. **Parental Generation (P):** 
  - **Homozygous scarlet-eyed males (ss)** were crossed with **Homozygous brown-eyed females (bb)**.

2. **First Filial Generation (F₁):**
  - The offspring from this cross were all of the wild-type (red-eyed), suggesting that red eye color is dominant over scarlet and brown eye color. The F₁ generation consisted of 1072 males and females with red eyes.

3. **Second Filial Generation (F₂):**
  - F₁ males were crossed with F₁ females. The offspring in the F₂ generation displayed a variety of eye colors:
    - 2684 wild-type (red-eyed) males and females
    - 891 scarlet-eyed males and females
    - 887 brown-eyed males and females
    - 298 white-eyed males and females

This experiment demonstrates classic Mendelian inheritance with a wild-type (red-eye) dominance and the appearance of two recessive traits (scarlet and brown eyes) along with the expression of other phenotypes such as white eyes due to possible genetic combinations.
Transcribed Image Text:### Genetic Cross Experiment: Eye Color in Drosophila #### Cross #1: **Parental Generation (P):** - Homozygous scarlet-eyed males (ss) - Homozygous brown-eyed females (bb) **First Filial Generation (F₁):** - Result: 1072 Wild-type (red-eyed) males and females **Second Filial Generation (F₂):** - Cross: F₁ males x F₁ females - Result: - 2684 wild-type males and females - 891 scarlet-eyed males and females - 887 brown-eyed males and females - 298 white-eyed males and females #### Explanation: In this genetic cross experiment, the purpose was to study the inheritance pattern of eye color in Drosophila melanogaster (fruit flies). 1. **Parental Generation (P):** - **Homozygous scarlet-eyed males (ss)** were crossed with **Homozygous brown-eyed females (bb)**. 2. **First Filial Generation (F₁):** - The offspring from this cross were all of the wild-type (red-eyed), suggesting that red eye color is dominant over scarlet and brown eye color. The F₁ generation consisted of 1072 males and females with red eyes. 3. **Second Filial Generation (F₂):** - F₁ males were crossed with F₁ females. The offspring in the F₂ generation displayed a variety of eye colors: - 2684 wild-type (red-eyed) males and females - 891 scarlet-eyed males and females - 887 brown-eyed males and females - 298 white-eyed males and females This experiment demonstrates classic Mendelian inheritance with a wild-type (red-eye) dominance and the appearance of two recessive traits (scarlet and brown eyes) along with the expression of other phenotypes such as white eyes due to possible genetic combinations.
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