in freshwater snails, pigment color is influenced by two genes. if two heterozygous pigmented freshwater snails were crossed and offspring were produced in a ratio of 9 pigmented snails to 7 albino snails, what are the genotypes of the offspring?
What are the genotypes of the offspring if two heterozygous pigmented freshwater snails were crossed and offspring were produced in a ratio of 9 pigmented snails to 7 albino snails?
Answer:
In this scenario, we are dealing with a dihybrid cross involving two genes. Let’s denote the genes responsible for pigment color as Gene A and Gene B.
The genotypes of the parent snails can be represented as follows:
Parent 1: AaBb
Parent 2: AaBb
When these two heterozygous pigmented freshwater snails are crossed, the Punnett square for the dihybrid cross would look like this:
| A a |
|---------|
B | AB aB |
b | Ab ab |
From the Punnett square, we can see that the offspring are produced in the following ratio:
- 9/16 of the offspring will have at least one dominant allele for both genes (pigmented snails)
- 3/16 of the offspring will be homozygous dominant for both genes (pigmented snails)
- 3/16 of the offspring will have one dominant and one recessive allele (pigmented snails)
- 1/16 of the offspring will be homozygous recessive for both genes (albino snails)
Therefore, the genotypes of the offspring based on the given ratio would be as follows:
- 3/16: A_BB
- 6/16: A_Bb
- 3/16: A_bb
So, the genotypes of the offspring would be 3/16 A_BB, 6/16 A_Bb, and 3/16 A_bb, resulting in a ratio of 9 pigmented snails to 7 albino snails.