Question

iii. cross a gray female, whose father was albino, with a heterozygous male.

1. what is the probability of getting gray offspring?
2. what is the probability of getting albino offspring?
3. how many possible genotypes are there among the offspring?
4. how many possible phenotypes are there among the offspring?
5. what is the probability of getting heterozygous offspring?
6. what is the probability of getting homozygous offspring?
7. what is the genotype of the female? how do you know?

1. what is the genotype of the male? how do you know?

iv. cross an albino female, whose father was gray, with a gray male, whose mother was albino.

1. what is the probability of getting gray offspring?
2. what is the probability of getting albino offspring?
3. how many possible genotypes are there among the offspring?
4. how many possible phenotypes are there among the offspring?
5. what is the probability of getting heterozygous offspring?
6. what is the probability of getting homozygous offspring?
7. what was the genotype of the father of the albino female?

Answer:

III. Cross a gray female (father was albino) with a heterozygous male

Step 1: Determine genotypes

• Let gray be dominant (\(G\)) and albino be recessive (\(g\)).
• Albino father of the female: genotype \(gg\) (recessive trait). He passes one \(g\) to the female.
• Female is gray (dominant phenotype), so her genotype must be \(Gg\) (since she received \(g\) from father, needs \(G\) to be gray).
• Male is heterozygous: genotype \(Gg\).

Step 2: Set up Punnett square

	\(G\)	\(g\)
\(g\)	\(Gg\)	\(gg\)

1. Probability of gray offspring

Gray genotypes: \(GG\), \(Gg\), \(Gg\) (3 out of 4).
Probability: \(\frac{3}{4}\) or \(75\%\).

2. Probability of albino offspring

Albino genotype: \(gg\) (1 out of 4).
Probability: \(\frac{1}{4}\) or \(25\%\).

3. Possible genotypes among offspring

Genotypes: \(GG\), \(Gg\), \(gg\) → 3 types.

4. Possible phenotypes among offspring

Phenotypes: gray (\(GG\), \(Gg\)) and albino (\(gg\)) → 2 types.

5. Probability of heterozygous (\(Gg\)) offspring

Heterozygous genotypes: \(Gg\), \(Gg\) (2 out of 4).
Probability: \(\frac{2}{4} = \frac{1}{2}\) or \(50\%\).

6. Probability of homozygous offspring

Homozygous genotypes: \(GG\), \(gg\) (2 out of 4).
Probability: \(\frac{2}{4} = \frac{1}{2}\) or \(50\%\).

7. Genotype of the female

The female’s genotype is \(Gg\). Her father (albino) has \(gg\), so he must pass \(g\). Since she is gray (dominant), she needs \(G\), so \(Gg\).

8. Genotype of the male

The male is heterozygous, so genotype \(Gg\) (given as “heterozygous male”).

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IV. Cross an albino female (father was gray) with a gray male (mother was albino)

Step 1: Determine genotypes

• Albino female: genotype \(gg\) (recessive trait).
• Her father was gray: he must be \(Gg\) (to pass \(g\) to albino daughter, and show gray phenotype).
• Gray male: his mother was albino (\(gg\)), so he received \(g\) from mother. He is gray (dominant), so genotype \(Gg\).

Step 2: Set up Punnett square

	\(G\)	\(g\)
\(g\)	\(Gg\)	\(gg\)

1. Probability of gray offspring

Gray genotypes: \(Gg\), \(Gg\) (2 out of 4).
Probability: \(\frac{2}{4} = \frac{1}{2}\) or \(50\%\).

2. Probability of albino offspring

Albino genotypes: \(gg\), \(gg\) (2 out of 4).
Probability: \(\frac{2}{4} = \frac{1}{2}\) or \(50\%\).

3. Possible genotypes among offspring

Genotypes: \(Gg\), \(gg\) → 2 types.

4. Possible phenotypes among offspring

Phenotypes: gray (\(Gg\)) and albino (\(gg\)) → 2 types.

5. Probability of heterozygous (\(Gg\)) offspring

Heterozygous genotypes: \(Gg\), \(Gg\) (2 out of 4).
Probability: \(\frac{2}{4} = \frac{1}{2}\) or \(50\%\).

6. Probability of homozygous offspring

Homozygous genotype: \(gg\), \(gg\) (2 out of 4).
Probability: \(\frac{2}{4} = \frac{1}{2}\) or \(50\%\).

7. Genotype of the albino female’s father

The father was gray (dominant) and had an albino daughter (\(gg\)). He must pass \(g\) to his daughter, so his genotype is \(Gg\) (dominant phenotype with one recessive allele to pass).

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Final Answers (III)

1. \(\boldsymbol{\frac{3}{4}}\)
2. \(\boldsymbol{\frac{1}{4}}\)
3. \(\boldsymbol{3}\)
4. \(\boldsymbol{2}\)
5. \(\boldsymbol{\frac{1}{2}}\)
6. \(\boldsymbol{\frac{1}{2}}\)
7. Genotype: \(\boldsymbol{Gg}\) (explanation: Father is \(gg\) (albino), so female gets \(g\); she is gray, so needs \(G\), hence \(Gg\).)
8. Genotype: \(\boldsymbol{Gg}\) (explanation: Given as heterozygous.)

Final Answers (IV)

1. \(\boldsymbol{\frac{1}{2}}\)
2. \(\boldsymbol{\frac{1}{2}}\)
3. \(\boldsymbol{2}\)
4. \(\boldsymbol{2}\)
5. \(\boldsymbol{\frac{1}{2}}\)
6. \(\boldsymbol{\frac{1}{2}}\)
7. Genotype: \(\boldsymbol{Gg}\) (explanation: Father is gray (dominant) and has an albino daughter (\(gg\)), so he must carry \(g\) (genotype \(Gg\)).)