Consider the following dihybrid cross involving two of Mendel\'s genes in pea pl

Question

Consider the following dihybrid cross involving two of Mendel's genes in pea plants that assort independently and exhibit simple dominance (W-violet flowers; w white flowers. T-axial flower position; t -terminal flower position). A plant with white, axial flowers was crossed with a plant that had violet, terminal flowers. All F1 progeny have violet, axial flowers. F1 plants are selfed to yield: (5 points) 653 plants with violet, terminal flowers 1756 plants with violet, axial flowers 702 plants with white, axial flowers 234 plants with white, terminal flowers a. b. c. d. What is your expected phenotypic ratio for the progeny from this cross? How many individuals would you expect in each phenotypic class among the progeny? Calculate the chi-square value rounded to two decimals, and the degrees of freedom. Do the results observed differ significantly from those expected at p

Explanation / Answer

1.What is the expected phenotypic ratio for the progeny from this cross?

Observed frequencies:

PHENOTYPE

FREQUENCY

Violet Axial

1756

Violet terminal

653

white Axial

702

white terminal

234

Total

3345

Expected ratios for unlinked traits:

TRAITS

RATIO

Violet Axial

9

Violet terminal

3

white Axial

3

white terminal

1

2. How many individuals would you expect in each phenotypic class among the progeny?

Violet Axial

Violet terminal

white Axial

white terminal

Total

Observed (O)

1756

653

702

234

3345

Expected (E)

1881.56

3345*9/16

627.187

3345*3/16

627.187

3345*3/16

209.06

3345*1/16

3345

3. Calculate the chi square value rounded to two decimals, and the degree of freedom.

Violet Axial

Violet terminal

white Axial

white terminal

Observed ( O)

1756

653

702

234

Expected (E)

1881.56

627.187

627.187

209.06

O-E

-125.56

25.813

74.813

24.94

(O-E)2/E

8.37

1.062

8.923

2.97

x2=(8.37+1.062+8.923+2.97)=21.325

Determine the degree of freedom (df)

In order to determine if the chi-squared value is statistically significant a degree of freedom must first be identified

The degree of freedom is calculated from the table of frequencies according to the following formula:

df = (m – 1) (n – 1)

Where: m = number of rows ; n = number of columns

For all dihybrid crosses, the degree of freedom should be: (number of phenotypes – 1)

4. Do the results observed differ significantly from those expected at p<0.05

Yes, the results observed differ significantly from those expected at p<0.05

  

PHENOTYPE

FREQUENCY

Violet Axial

1756

Violet terminal

653

white Axial

702

white terminal

234

Total

3345

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.