Please answer my science question (in detail if possible)
Q: in rats the gene for black hair colour is dominant over the gene for brown hair colour. Draw a plunnet square and use it to predict the fractions of both the genotypes and phenotypes produced when two heterozygous rats mate
Thank you
Both are Bb.
https://www.google.com/search?client=safari&rls=en&q=punnett+square&ie=UTF-8&oe=UTF-8&gws_rd=ssl
To predict the fractions of genotypes and phenotypes in the offspring, we can use a Punnett square. This square allows us to visualize all the possible combinations of alleles that can be inherited from both parents.
In this case, we know that the gene for black hair color (B) is dominant over the gene for brown hair color (b). Let's assign the genotype of a rat with black hair color as BB and the genotype of a rat with brown hair color as bb. The heterozygous genotype, which will be one of the parents, will be Bb.
To create a Punnett square for this cross, we place the alleles of one parent on the top row and the alleles of the other parent on the left column. We then combine the alleles to determine the possible genotypes and phenotypes of the offspring.
Here is how the Punnett square for this cross would look like:
| B | b |
---------------------------------------
B | BB | Bb |
---------------------------------------
b | Bb | bb |
In this square, four possible combinations of alleles can be made: BB, Bb, Bb, and bb. Now, let's determine the genotypes and corresponding phenotypes for each combination.
1. BB: This genotype represents homozygous dominant rats, which will have black hair color.
2. Bb: This genotype represents heterozygous rats, which will also have black hair color since the black allele is dominant.
3. Bb: Similarly, this genotype represents heterozygous rats with black hair color.
4. bb: This genotype represents homozygous recessive rats, which will have brown hair color.
So, based on the Punnett square, we can predict the following fractions for both the genotypes and phenotypes:
- 1/4 (25%) probability of producing homozygous dominant rats with black hair (BB)
- 2/4 (50%) probability of producing heterozygous rats with black hair (Bb)
- 1/4 (25%) probability of producing homozygous recessive rats with brown hair (bb)
Therefore, when two heterozygous (Bb) rats mate, there is a 25% chance of producing rats with brown hair (bb) and a 75% chance of producing rats with black hair (BB or Bb).