You are given two true‑breeding groups of gerbils. the gerbils in the first group have black fur and curly tails; the gerbils in the second group have yellow fur and straight

General
1

you are given two true‑breeding groups of gerbils. the gerbils in the first group have black fur and curly tails; the gerbils in the second group have yellow fur and straight tails. when you produce an f1 generation, you see only gerbils with black fur and curly tails. when you produce an f2 generation, you see that 75% of the gerbils have black fur and 25% have yellow fur. you also see that 25% of the gerbils have straight tails and 75% have curly tails. if the single alleles responsible for coat color and tail appearance sort independently, how many of the black gerbils in this generation are expected to have straight tails?

2

How many of the black gerbils in this generation are expected to have straight tails?

Answer:
In this scenario, we are dealing with two traits in gerbils: coat color and tail appearance. Given that the alleles for coat color and tail appearance sort independently, we can use the principles of Mendelian genetics to analyze the situation.

Let’s denote the alleles:

  • B for black coat color
  • b for yellow coat color
  • C for curly tails
  • c for straight tails

From the information given, we know that the F1 generation consists of black gerbils with curly tails. This indicates that the parental gerbils were both homozygous dominant (BBCC).

When these gerbils are crossed, the F2 generation shows a phenotypic ratio of 75% black (3/4) and 25% yellow (1/4) in terms of coat color. Additionally, the F2 generation shows a phenotypic ratio of 75% curly tails (3/4) and 25% straight tails (1/4).

Now, when we focus on the black gerbils in the F2 generation, we need to determine how many of them are expected to have straight tails. Since coat color and tail appearance are inherited independently, we need to consider each trait separately.

  1. For coat color (black): 75% of the black gerbils (3/4) will have the genotype BB, and 25% will have the genotype Bb.
  2. For tail appearance (straight tail): 25% of the F2 gerbils are expected to have straight tails.

When we multiply the probabilities of these two traits together, we find the expected frequency of black gerbils with straight tails:
(25% of black gerbils) x (25% with straight tails) = 6.25%

Therefore, approximately 6.25% of the black gerbils in this generation are expected to have straight tails.