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Home Q & A Board Biology-Related Homework Help Genetics and Developmental Biology
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riyaghuman riyaghuman
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11 years ago
I need help with biology home work Please help me! the full question is black fur is dominant to white fur in rabbits, what would be the genotype and phenotype ratios resulting from the following crosses.

1.Homozyous black and homozygous white


2.Two Heterozygous


3.A Heterozygous black and white.
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#1
11 years ago
1. 4:0
2. 3:1
3. 3:1

Isn't 2 and 3 basically the same question?
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rixa85rixa85
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11 years ago
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#3
11 years ago
Remember, genotype means the combinations of alleles.
Phenotype means what trait the organism (in this case, rabbits) display.

Let trait for black be Y and let trait for white be y

1.Homozyous black and homozygous white

So homozygous black would be YY
Homozygous white would be yy

YY x yy would give you 4 of the same, which would be (Yy)
The genotypic ratio would just be 1 because all offspring would have the same combination of this trait.
The phenotypic ratio would also be 1 because all offspring would be the same colour.

2.Two Heterozygous

Yy x Yy
This cross would give you YY, Yy, Yy, and yy
The genotypic ratio would be 1:2:1 because, as you can see, the two genotypes in the middle are the same.
The phenotypic ratio would also be 3:1 because the rabbits with YY and Yy genotypes would display black fur, while only the rabbit with a yy genotype would display the white fur.

3.A Heterozygous black and white.

Yy x yy
This cross would give you Yy, Yy, yy, yy,
The genotypic ratio would be 2:2, which is then reduced to 1:1.
The phenotypic ratio would also be 2:2, which is then reduced to 1:1.

Hope this helped!
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