# Question: questions 10 14 are based on the following situation...

###### Question details

Questions 10 - 14 are based on the following situation.

The F2 generation from a dihybrid cross produced a total of
356 tall plants with purple flowers, 124 tall plants with pink
flowers, 107 short plants with purple flowers, and 22 short plants
with pink flowers.

You will use the Chi-square goodness-of-fit test to determine
whether these values are significantly different from the expected
values.

In order to do this, we must first identify a hypothesis. For
a genetic cross, we postulate what phenotypic ratio we would expect
and then we perform the Chi-square goodness-of-fit test to evaluate
how well our observed and expected numbers agree.

For this dihybrid cross, you decide to assume that the plants
in our F2 generation follow a phenotypic ratio of 9:3:3:1 and then
let the results from the Chi-square goodness-of-fit test tell you
if this prediction is accurate.

10. Fill in the following table with the expected numbers (E)
of plants from the F2 generation for the phenotypes listed. Please
note that the observed numbers (O) have been inputted for you
already. (5 marks)

(HINT: You will need to use your hypothesis to perform these
calculations.)

When inputting the numbers that you calculated for the
expected (E), please round to the nearest whole number (e.g.
52).

Phenotype Observed (O) Expected (E)

Tall plant with purple flowers 356

Tall plant with pink flowers 124

Short plant with purple flowers 107

Short plant with pink flowers 22

Total number of plants in the F2 generation 609 **

Make sure your total number of plants are the same for the
observed and expected columns (use this to check your expected
calculations)

**This question is based on the information provided in Questions 10.**

Please note that on an examination, you will NOT be given the
formula for the Chi-square value.

11. What is the Chi-square value between the observed and
expected offspring in the F2 generation for this dihybrid cross?
Please give answer to 3 decimal places

**This question is based on the information provided in Questions 10-11**.

Please note that on an examination, a Table of Critical values
of the chi-square distribution will be provided.

**12. Please answer the following:**

(a) What is the degrees of freedom for this dihybrid
cross?

(1 mark)

(b) What is the probability associated with your calculated
chi-square value for this dihybrid cross? (2 marks)

**The following question is based on question 10-13**

13.

**Please answer the following based on your Chi-square goodness-of-fit test results.**(a) Is the difference between the observed and expected
numbers of progeny in the F2 generation the result of chance? Do
your results support the hypothesis given above in Question 10?
Answer yes or no. (0.5 mark)

(b) Briefly explain how you arrived at the answer given in
part (a). (1.5 marks)

**The following is based on the information provided in Questions 10 - 13**

14.

**Please answer the following based on your Chi-square goodness-of-fit test results.**(a) Do you think the genes for plant height and flower colour
are linked? Answer yes or no. (0.5 mark)

(b) Briefly, explain how you arrived at the answer given in
part (a), making reference to Mendel's law of independent
assortment. (1.5 marks)