We make a dihybrid cross of genotype PpIi and genotype PpIi . The gene symbols a

Question

We make a dihybrid cross of genotype PpIi and genotype PpIi. The gene symbols are as follows:

P : purple petals

p : white petals

I : inflated pods

i : pinched pods

Both of the parents (the dihybrids) have a phenotypeof purple petals and inflated pods. We also know that the genetic mechanism is simple dominance for both genes, and that inheritance of one gene is not affected by inheritance of the other gene.

We see four phenotypes in the progeny:

Purple petals and inflated pods

Purple petals and pinched pods

White petals and inflated pods

White petals and pinched pods

We want to use statistics to determine if the expected phenotypic ratio within the progeny holds true. Complete the table below by filling out the blank spaces. Use your filled-in table to answer parts a few more questions, then evaluate the final statement as true or false.

HINT: you may want to consult the lecture slides to remind yourself what the expected phenotypic ratio is for the progeny. You will use this to help you fill out the "Expected" column.

(Please format your answers as follows: for the "Expected" column, type in a whole number; for the (O-E) column, type in a whole integer (can be positive or negative); for the (O-E)2 column, type in a whole number; and for the (O-E)2/E column, you will need to type in a non-whole number, rounded to the nearest hundredth. Examples of answer format--but NOT actual statistics--are shown in red in the table below.)

Now, use the table that you just filled in to answer the following questions:

What is the chi-square statistic (x2)? (Type in your answer as a non-whole number, rounded to the nearest hundredth. Example of answer formatting: 1.23.)

What is/are the degrees of freedom? (Type in your answer as a one-digit whole number.)

Given the degrees of freedom that you just stated, the critical chi-square (x2) value at a p-value of 0.05 is what? Look this up on the chi-square table provided at the end of this question. (Type in your answer as a non-whole number, rounded to the nearest hundredth. Example of answer formatting: 1.23.)

According to the statistics that you just calculated in parts a-c, which of the following two statements is true? (Type in a "1" or a "2", corresponding to your choice of the two statements below.)

1. There is enough evidence to reject the hypothesis of a 1:2:1 ratio at a p-value of 0.05.

2. There is NOT enough evidence to reject the hypothesis of a 1:2:1 ratio at a p-value of 0.05.

Expected Observed (O-E) (O-E)2 (O-E)2/E Example of answer format 123 - -12 123 1.23 Purple petal and inflated pod 866 Purple petal and pinched pod 345 White petal and inflated pod 303 White petal and pinched pod 86 TOTAL 1,600 - -

Explanation / Answer

fAccording to null hypothesis and chi quare start there is NOT enough evidence to reject the hypothesis of 1:2:1 ratio at a p level of 0.05

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