In guinea pigs, black fur (B) is dominant over white fur (b). Cross a heterozygous (hybrid) black guinea pig with a homozygous (purebred) white guinea pig. Complete a Punnett square, identify the genotype(s), phenotype(s), and probability (% and fraction) that the offspring will be black and white?
1/2 of the offspring (50%) will be heterozygous black ... Bb
1/2 of the offspring (50%) will be homozygous white ... bb
Oh, guinea pig genetics! Let's dive into it!
First, let's represent the black fur allele as 'B' (dominant) and the white fur allele as 'b' (recessive).
The heterozygous black guinea pig's genotype is Bb (since it carries both black and white alleles), and the purebred white guinea pig's genotype is bb (since it only carries the white allele).
Now, let's make a Punnett square:
| B | b |
-----------------
B | BB | Bb |
-----------------
b | Bb | bb |
From the Punnett square, we can see that there are two possible genotypes for the offspring: BB and Bb. Both of these genotypes correspond to black phenotypes.
Therefore, the probability that the offspring will be black is 100% (1/1) or 100% (2/2) if you prefer percentages.
As for white, there is no genotype that results in a white phenotype when crossed with a heterozygous black guinea pig. So, the probability of getting white offspring is 0%.
Remember, in this case, black fur is dominant over white fur, so only the presence of the black allele will determine the phenotype.
To determine the genotype, phenotype, and probability of offspring being black or white, we can create a Punnett square. In this case, the dominant trait is black fur (B) and the recessive trait is white fur (b).
Let's use the letters "B" and "b" to represent the alleles:
Genotype of the black guinea pig (hybrid Bb): Bb
Genotype of the white guinea pig (purebred bb): bb
To create the Punnett square, we will cross the two guinea pigs by placing the alleles from each parent along the top and left side of the square:
| B | b |
-----------------------------------
| | |
B | BB | Bb |
| | |
-----------------------------------
| | |
b | Bb | bb |
| | |
Now we can identify the genotype and phenotype of each offspring:
- BB: This represents a black guinea pig. Genotype: BB, Phenotype: Black
- Bb: This also represents a black guinea pig. Genotype: Bb, Phenotype: Black
- bb: This represents a white guinea pig. Genotype: bb, Phenotype: White
Based on the Punnett square, there are 2 possible outcomes for black guinea pigs (BB and Bb), and only 1 outcome for white guinea pigs (bb).
Probability of black guinea pigs = (Number of black guinea pigs / Total number of offspring) = (2 / 4) = 1/2 = 50%
Probability of white guinea pigs = (Number of white guinea pigs / Total number of offspring) = (1 / 4) = 1/4 = 25%
So, there is a 50% chance (or 1/2) that the offspring will be black, and a 25% chance (or 1/4) that the offspring will be white.
To solve this problem, let's first understand the genetics behind fur color in guinea pigs.
In guinea pigs, black fur (B) is dominant over white fur (b). This means that if a guinea pig has even one copy of the black fur allele (B), it will have black fur.
Now, let's analyze the cross between a heterozygous black guinea pig (Bb) and a homozygous white guinea pig (bb). The genotype of the hybrid black guinea pig (Bb) indicates that it has one copy of the black fur allele (B) and one copy of the white fur allele (b). The genotype of the white guinea pig is bb, meaning it has two copies of the white fur allele (b).
To create a Punnett square, we will write the possible gametes of each parent along the top and left side of the square.
For the heterozygous black guinea pig (Bb), the possible gametes are:
B
b
For the homozygous white guinea pig (bb), the only possible gametes are:
b
b
Now, we can combine these gametes by filling in the boxes of the Punnett square:
| B | b |
-------------------
b | Bb | bb |
b | Bb | bb |
From this Punnett square, we can determine the potential genotypes and phenotypes of the offspring:
- Genotype: There are two possible genotypes for the offspring. They can either be heterozygous black (Bb) or homozygous white (bb).
- Phenotype: Since black fur (B) is dominant over white fur (b), any offspring with at least one black fur allele (Bb or BB) will have black fur. Only the homozygous offspring with two white fur alleles (bb) will have white fur.
Now, let's calculate the probabilities:
- Probability of black offspring: There are three out of four possible combinations that result in black fur (Bb and BB). This represents a 75% chance or a 3/4 probability.
- Probability of white offspring: There is one out of four possible combinations that result in white fur (bb). This represents a 25% chance or a 1/4 probability.
To summarize:
- The probability of the offspring being black is 75% (3/4).
- The probability of the offspring being white is 25% (1/4).
Remember, these probabilities are based on the assumption that the traits follow simple Mendelian inheritance and independent assortment.