A true breeding brown mouse is mated with a true-breeding white mouse and all their offspring are brown. If two of these brown offspring are mated, what percentage of the F1 and F2 generations will be brown?
If you mean homozygous by "true breeding," Brown is dominant over white, because all of F1 generation are all brown (Bw). If two Bw's mate, use the Punnett Square for F2.
http://en.wikipedia.org/wiki/Punnett_square
To determine the percentage of brown mice in the F1 and F2 generations, we need to understand the genetic basis of the brown and white fur color in mice.
Let's assign the letter "B" to represent the gene for brown fur color and the letter "b" to represent the gene for white fur color. Since the true breeding brown mouse is mated with a true breeding white mouse, we can infer that the brown mouse is homozygous (BB) and the white mouse is also homozygous (bb).
When these two parents are crossed, all their offspring are brown. This indicates that brown fur color (B) is dominant over white fur color (b). Therefore, the genotype of the offspring from the cross is heterozygous (Bb), with brown fur being expressed.
Now, if two of these brown offspring (Bb) are mated, we can use a Punnett square to determine the potential genotypes and phenotypes of the F1 and F2 generations.
F1 Generation:
When two brown mice (Bb x Bb) are crossed, the possible genotypes of the offspring are BB, Bb, and bb. Since BB and Bb both have at least one dominant B allele, all the F1 generation mice will be brown (100% brown).
F2 Generation:
To determine the potential genotypes in the F2 generation, we need to cross the F1 generation brown mice (Bb) with each other. The possible genotypes in the F2 generation are BB, Bb, and bb.
Using a Punnett square, we find that the percentage breakdown of the genotypes in the F2 generation is as follows:
- 25% BB (brown)
- 50% Bb (brown)
- 25% bb (white)
So, 75% of the F2 generation will have brown fur (BB or Bb), and 25% will have white fur (bb).
To summarize:
- F1 generation: 100% brown
- F2 generation: 75% brown, 25% white
To determine the percentage of brown mice in the F1 and F2 generations, we need to understand the principles of inheritance and use Punnett squares.
In this scenario, a true-breeding brown mouse and a true-breeding white mouse are crossed, resulting in all brown offspring. This indicates that the brown trait is dominant, and the white trait is recessive.
When two of these brown offspring are mated, we can use a Punnett square to predict the possible outcomes.
In the Punnett square, we represent the alleles of each parent. Let's use "B" to represent the dominant brown allele and "b" for the recessive white allele.
Parents' genotype: BB x BB
Punnett square:
| B | B |
-----------------
B | BB | BB |
-----------------
B | BB | BB |
From the Punnett square, we can see that all F1 generation (offspring of the brown parents) will have the genotype BB, resulting in brown fur. Therefore, 100% of the F1 generation will be brown.
Now, let's focus on the F2 generation, which is the result of mating two F1 individuals (BB x BB).
Parents' genotype: BB x BB
The possible genotypes in the F2 generation are as follows:
BB (brown)
BB (brown)
BB (brown)
BB (brown)
Based on these genotypes, we can conclude that 100% of the F2 generation will also be brown.
Therefore, both the F1 and F2 generations will have 100% brown mice.
In summary, the percentage of brown mice in both the F1 and F2 generations will be 100%.