When true-breeding Azule flowers (BB) expressing a blue color, were crossed with

Question

When true-breeding Azule flowers (BB) expressing a blue color, were crossed with Azule flowers expressing no color (bb); the F_1 progeny resulted in all blue flowers. The owner crossed the F_1 generation, which resulted in 66 blue and 20 white (no color) flowers. The critical value is 3.84 for this experiment. Perform a Chi square to test your hypothesis that flowers color is controlled by a single gene? Be sure to state whether your hypothesis is rejected to accepted. Show all your work including expected

Explanation / Answer

When purelines are crossed, always F1 generation will be heterozygotes. As expected all F1 generation plants are showing dominat phenotype (i.e., Blue color). Their genotype will be Bb. 3;1 ratio of blue and white flower plants are expected when F1 generation is crossed.

As per the information given in the question, there 86 plants for which flower colr observed (66 blue + 20 white = 86.)

3/4 of 86 = 64.5

1/4 of 86 = 21.5

In chi-square test, we have to first calculate the value of ² from observed and expected frequencies.

² = the sum of (o e)²e

where: o = observed number of individuals; e = expected number of individuals

Observed and expected frequencies for Blue are 66 and 64.5.

(66-64.5)2 x 64.5 = 145.125

Observed and expected frequencies for white are 20 and 21.5.

(20-21.5)2 x 21.5 = 48.375

Some of both values is = 145.125 + 48.375 = 193.5 = ²

Caluculated ² value (193.5) is greater than the critical value (3.84), null hypothesis should be rejected and alternative hypothesis should be accepted.

So, the conclusion is flower color is controlled by a single gene.

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