Question

two inbred lines of drosophila are crossed, and the f1 generation has a mean number of abdominal bristles of 20 and a standard deviation of 2. the f2 generation has a mean of 20 and a standard deviation of 3. what are the environmental variance, the genetic variance and the broad-sense heritability of bristle number in this population? g

Answer 1

To calculate the environmental variance, subtract the genetic variance from the total variance. The genetic variance can be calculated using the formula and Broad-sense heritability is calculated using the genetic variance divided by the total variance.

Step-by-step explanation:

The environmental variance, genetic variance, and broad-sense heritability of bristle number in the population can be calculated based on the means and standard deviations of the F1 and F2 generations.

To calculate the environmental variance, subtract the genetic variance from the total variance. The total variance is the square of the standard deviation, so for the F1 generation, the total variance is 2^2 = 4.

The genetic variance can be calculated using the formula:

Genetic variance = (Mean of F2 - Mean of F1) / 2

In this case, the genetic variance is (20 - 20) / 2 = 0.

Finally, the broad-sense heritability can be calculated using the formula:

Broad-sense heritability = Genetic variance / Total variance

In this case, the broad-sense heritability is 0 / 4 = 0.

Answer 2

Step-by-step explanation:

To calculate the environmental variance, genetic variance, and broad-sense heritability, we can use the following formulas:

Vp = Vg + Ve (where Vp is the phenotypic variance, Vg is the genetic variance, and Ve is the environmental variance)

H^2 = Vg/Vp (where H^2 is the broad-sense heritability)

Given that the mean number of abdominal bristles in the F1 generation is 20, and the standard deviation is 2, we can calculate the phenotypic variance as:

Vp = (2^2) = 4

Since the F1 generation is a result of a cross between two inbred lines, we can assume that all of the genetic variation in the F1 generation is due to dominance effects, and the genetic variance in the F1 generation is zero.

Therefore,

Vp = Vg + Ve

4 = 0 + Ve

Ve = 4

To calculate the broad-sense heritability, we can use the formula:

H^2 = Vg/Vp

Since Vg is zero in the F1 generation, the broad-sense heritability for this generation is also zero.

Moving on to the F2 generation, we are given that the mean number of abdominal bristles is 20, and the standard deviation is 3. We can calculate the phenotypic variance as:

Vp = (3^2) = 9

To calculate the genetic variance, we can use the formula:

Vg = Vp - Ve

We know that Ve is 4, so:

Vg = 9 - 4 = 5

To calculate the broad-sense heritability, we can use the formula:

H^2 = Vg/Vp

H^2 = 5/9

H^2 = 0.56 (rounded to two decimal places)

Therefore, the environmental variance is 4, the genetic variance is 5, and the broad-sense heritability is 0.56 for bristle number in this population.