"In guinea pigs, a spotted coat is dominant to uniform coat colour. If a heterozygous spotted coat guinea pig is bred with a uniform coat guinea pig, use a Punnett square to determine the genotypic and phenotypic ratios of the offspring."
To determine the genotypic and phenotypic ratios of the offspring when a heterozygous spotted coat guinea pig (Ss) is bred with a uniform coat guinea pig (ss), we can use a Punnett square.
First, let's write out the genotypes of the parent guinea pigs:
Spotted coat guinea pig (heterozygous): Ss
Uniform coat guinea pig: ss
To create the Punnett square, we place the alleles from the parents along the top and left sides:
| S s
---------------------
S | SS Ss
s | sS ss
Now, we can fill in the boxes of the Punnett square by combining the alleles from the parent guinea pigs.
For the first box:
The top letter is S from the spotted coat guinea pig, and the left letter is s from the uniform coat guinea pig. Thus, the genotype of the offspring in the first box is Ss.
For the second box:
The top letter is S from the spotted coat guinea pig, and the left letter is s from the uniform coat guinea pig. Thus, the genotype of the offspring in the second box is Ss.
For the third box:
The top letter is s from the spotted coat guinea pig, and the left letter is S from the uniform coat guinea pig. Thus, the genotype of the offspring in the third box is sS.
For the fourth box:
The top letter is s from the spotted coat guinea pig, and the left letter is s from the uniform coat guinea pig. Thus, the genotype of the offspring in the fourth box is ss.
Now, let's determine the phenotypes of the offspring based on the genotypes:
- For genotypes SS and Ss: Both genotypes have at least one S allele, which results in a spotted coat. Therefore, the phenotypes for these genotypes are spotted coat.
- For genotype ss: This genotype has no S allele, resulting in a uniform coat. Therefore, the phenotype for this genotype is uniform coat.
Now, we can summarize the genotypic and phenotypic ratios of the offspring:
- Genotypic ratio:
- SS: 1/4 (25%)
- Ss: 2/4 (50%)
- ss: 1/4 (25%)
- Phenotypic ratio:
- Spotted coat: 3/4 (75%)
- Uniform coat: 1/4 (25%)
Therefore, when a heterozygous spotted coat guinea pig is bred with a uniform coat guinea pig, the offspring are expected to have a genotypic ratio of 1:2:1 (SS:Ss:ss) and a phenotypic ratio of 3:1 (spotted coat:uniform coat).
To determine the genotypic and phenotypic ratios of the offspring when a heterozygous spotted coat guinea pig is bred with a uniform coat guinea pig, you can use a Punnett square.
First, let's determine the genotypes of the parent guinea pigs.
The heterozygous spotted coat guinea pig has the genotype Ss, where "S" represents the dominant allele for a spotted coat and "s" represents the recessive allele for a uniform coat.
The uniform coat guinea pig is homozygous for the recessive allele, ss.
Now let's construct a Punnett square to determine the possible genotypes and phenotypes of the offspring:
| s | s |
-----------------|------------------|------------------|
S | Ss | Ss |
-----------------|------------------|------------------|
s | Ss | Ss |
-----------------|------------------|------------------|
In the Punnett square, the possible combinations of alleles are shown. Each box represents one possible genotype of an offspring.
From the Punnett square, we can see that there are four possible genotypes: SS, Ss, sS, and ss.
Now, let's determine the phenotypes of the offspring based on the genotypes. Since the spotted coat is dominant to the uniform coat, any guinea pig with at least one "S" allele will have a spotted coat, while guinea pigs with two "s" alleles will have a uniform coat.
Based on the genotypes obtained from the Punnett square, we can determine the phenotypic ratios:
- The genotypes SS and Ss both result in a spotted coat. So, 3 out of 4 possible genotypes will have a spotted coat.
- The genotype ss will result in a uniform coat. So, 1 out of 4 possible genotypes will have a uniform coat.
Therefore, the phenotypic ratio of the offspring will be 3:1 with respect to their coat coloring, with three guinea pigs having a spotted coat and one guinea pig having a uniform coat.