Question

C-Fern Data

Gametophytes:

            Green: 116

            Pale: 146

Sporophytes

            Green: 168

            Pale: 72

Construct a chi-square table using the provided sporophyte data assuming the green allele is dominant. (use the same format as in your lab manual—you must include all values) (4 points)

Explain the genetic basis for how you determined the expected ratios if the green allele were dominant. (A Punnett square might be a useful tool for your explanation) (2 points)

What are the degrees of freedom? (1 point)

Based on your calculations, do you reject or fail to reject your hypothesis? (Use table in the lab manual. Your probability value is 0.05)

Answer 1

1ST PART:

Expected ratio- 3:1

total number = 168 + 72 = 240

number of expected green sporophytes = 0.75*240 = 180

number of expected pale sporophytes = 0.25*240 = 60

Chi-square table:

	OBSERVED	EXPECTED	(O-E)2/E
GREEN	168	180	0.8
PALE	72	60	2.4
TOTAL	240	240	X2= 3.2

2ND PART:

Let, A and a be the dominant and recessive allele respectively,

A_ : Green, aa: pale

PUNETT-SQUARE: Cross: Aa X Aa

	A	a
A	AA	Aa
a	Aa	aa

genotypic ratio- 1:2:1 ( 1/4 AA: 1/2 Aa: 1/4 aa)

phenotypic ratio- 3:1 (3/4 green: 1/4 pale)

3RD PART:

Degree of freedom = 2 - 1 = 1

4rth PART:

For p less than or equal to 0.05, we fail to reject the hypothesis