Question

Corn #2 is a standard F2 generation dihybrid cross. The traits you will be following is color and seed shape. The following counts, in red, were determined in the lab

Number of yellow, round 147

Number of purple, round 452

Number of yellow, wrinkled 43 Number of purple, wrinkled 151

What is the expected ratio? Perform a chi square below. Determine your probability value ______ and analyze what that means.

Answer 1

The results given is of a dihybrid cross. The phenotypic ratio of dihybrid cross is 9:3:3:1

Given that

Number of purple, round 452

Number of purple, wrinkled 151

Number of yellow, round 147

Number of yellow, wrinkled 43

We have to test whether the number of different colored seeds follow 9:3:3:1.

ie Expected ratio is 9:3:3:1

Chi-square Test

Our Null hypothesis is " There is no significant difference between the expected and observed ratio (ie the given ratios follows (9:3:3:1 ratio)

To do the Chi-square test follow the formula, where O is observed value, E is Expected values

Degrees of freedom = 3

Probability level = 0.05 (95%)

Tabled Chi-square value at 3 degrees of freedom is 7.815)

If the calculated Chi-square value is lesser than the tabled value, we accept our null hypothesis

The calculations of Chi-square are given below

Here at 3 degrees of freedom, and 0.05 probability level the calculated value (1.0018) of χ² is lesser than tabled value (7.815) Therefore the Null hypothesis is accepted. ie the ratios follow 9:3:3:1 ratio