multiple choice question
in fruit flies, grey body color (g) is dominant to black body color (g), and long wings (l) is dominant to tiny wings, known as vestigial wings, (l). the genes for body color and wing length are linked. the punnett square shows a cross between a fly that is homozygous for a grey body and heterozygous for long wings and a fly that is heterozygous for a grey body and homozygous for vestigial wings.
what are the possible phenotypes of the offspring?
| | gl | gl |
|---|---|---|
| gl | | |
| gl | | |
- 1:1 ratio of black body, vestigial wings and black body, long wings
- all offspring will have grey body and long wings
- 1:1 ratio of grey body, long wings and grey body, vestigial wings
- all offspring will have grey body and vestigial wings

Question

multiple choice question
in fruit flies, grey body color (g) is dominant to black body color (g), and long wings (l) is dominant to tiny wings, known as vestigial wings, (l). the genes for body color and wing length are linked. the punnett square shows a cross between a fly that is homozygous for a grey body and heterozygous for long wings and a fly that is heterozygous for a grey body and homozygous for vestigial wings.
what are the possible phenotypes of the offspring?
|   | gl | gl |
|---|---|---|
| gl |   |   |
| gl |   |   |
- 1:1 ratio of black body, vestigial wings and black body, long wings
- all offspring will have grey body and long wings
- 1:1 ratio of grey body, long wings and grey body, vestigial wings
- all offspring will have grey body and vestigial wings

Accepted Answer

# Explanation:
## Step1: Determine Parent Genotypes
First fly: Homozygous grey body ($GG$) and heterozygous long wings ($Ll$), so genotype $GGLl$. Gametes: $GL$, $Gl$.
Second fly: Heterozygous grey body ($Gg$) and homozygous vestigial wings ($ll$), so genotype $Ggll$. Gametes: $Gl$, $gl$. Wait, correction: Wait, original problem says second fly is heterozygous grey ($Gg$) and homozygous vestigial ($ll$)? Wait no, re-reading: "a fly that is homozygous for a grey body and heterozygous for long wings" (first fly: $GGLl$) and "a fly that is heterozygous for a grey body and homozygous for vestigial wings" (second fly: $Ggll$). Wait, no—wait, body color: grey is dominant ($G$), black is $g$. First fly: homozygous grey ($GG$), heterozygous long wings ($Ll$): so $GGLl$, gametes $GL$, $Gl$. Second fly: heterozygous grey ($Gg$)? Wait no, wait the problem says "heterozygous for a grey body"—no, wait, maybe typo? Wait, no: first fly: homozygous grey ($GG$), heterozygous long wings ($Ll$): $GGLl$. Second fly: heterozygous grey ($Gg$)? No, wait, no—wait, the second fly: "heterozygous for a grey body" would be $Gg$, but vestigial wings are $ll$ (homozygous). Wait, but the Punnett square has columns $GL$, $Gl$ and rows $Gl$, $gl$? Wait, maybe the second fly is $Ggl l$? Wait, no, let's re-express.

Wait, first fly: $GGLl$ (homozygous grey, heterozygous long wings) → gametes: $GL$ (from $GG$ and $L$) and $Gl$ (from $GG$ and $l$).

Second fly: "heterozygous for a grey body" ($Gg$) and "homozygous for vestigial wings" ($ll$) → genotype $Ggll$. Wait, but $Ggll$ would produce gametes $Gl$ (from $G$ and $l$) and $gl$ (from $g$ and $l$). But the Punnett square in the problem has rows $Gl$ and $gl$? Wait, the Punnett square shown has rows $Gl$ and $gl$, columns $GL$ and $Gl$. Wait, maybe the second fly is actually $Ggl l$? No, maybe I misread. Wait, the problem says "a fly that is heterozygous for a grey body and homozygous for vestigial wings"—so $Ggll$, but then gametes would be $Gl$ and $gl$. But the Punnett square has two rows: $Gl$ and $gl$, two columns: $GL$ and $Gl$. Wait, maybe the second fly is $Ggl l$ but actually, maybe the first fly is $GGLl$ (gametes $GL$, $Gl$) and the second fly is $Ggl l$? No, wait, no—maybe the second fly is $Ggl l$ but that's not possible. Wait, perhaps the second fly is $Ggl l$ but actually, the key is: body color: $G$ is dominant, so any $G-$ (homo or hetero) is grey. Wings: long ($L$) dominant over vestigial ($l$).

First fly: $GGLl$ (gametes $GL$, $Gl$). Second fly: Let's check the Punnett square rows: $Gl$ and $gl$? Wait, the Punnett square has rows $Gl$ and $gl$, columns $GL$ and $Gl$. So crossing $GL, Gl$ (columns) with $Gl, gl$ (rows).

Now, let's do the Punnett square:

- $GL \times Gl$: $GGLl$ (grey, long wings)
- $GL \times gl$: $GgLl$ (grey, long wings)
- $Gl \times Gl$: $GGll$ (grey, vestigial wings)
- $Gl \times gl$: $Ggll$ (grey, vestigial wings)

Wait, no—wait, the rows are $Gl$ and $gl$, columns $GL$ and $Gl$. Wait, maybe the second fly is $Ggl l$ but actually, the first fly is $GGLl$ (gametes $GL, Gl$) and the second fly is $Ggl l$ (gametes $Gl, gl$)? No, that can't be. Wait, maybe the second fly is $Ggl l$ but the problem says "homozygous for vestigial wings"—so $ll$, so genotype $Ggll$, gametes $Gl, gl$. Then the Punnett square would be:

Columns (first fly): $GL, Gl$
Rows (second fly): $Gl, gl$

So:

1. $GL \times Gl$: $GGLl$ (grey, long)
2. $GL \times gl$: $GgLl$ (grey, long)
3. $Gl \times Gl$: $GGll$ (grey, vestigial)
4. $Gl \times gl$: $Ggll$ (grey, vestigial)

Wait, but that would be 2 grey long and 2 grey vestigial, so 1:1 ratio of grey long and grey vestigial. Wait, but the options: "1:1 ratio of grey body, long wings and grey body, vestigial wings" is an option. Let's check the options:

- Option 1: black body (no, since all have $G-$), so wrong.
- Option 2: all long wings? No, some vestigial.
- Option 3: 1:1 grey long and grey vestigial.
- Option 4: all vestigial? No, some long.

So the correct answer is the third option: 1:1 ratio of grey body, long wings and grey body, vestigial wings.

## Step2: Analyze Phenotypes
All offspring have grey body (since $G$ is dominant, and all have $G-$ genotype: $GG$ or $Gg$). For wings: half have long wings ($Ll$ or $Ll$) and half have vestigial ($ll$). So the ratio is 1:1 for grey long and grey vestigial.

# Answer:
1:1 ratio of grey body, long wings and grey body, vestigial wings (the third option)

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Explanation:

Step1: Determine Parent Genotypes

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