1. An ear of corn has a total of 381 grains, including 216 Purple & Smooth, 79 Purple & Shrunken, 65 Yellow & Smooth, and 21 Yellow & Shrunken.

Your Tentative Hypothesis: This ear of corn was produced by a dihybrid cross involving two pairs of heterozygous genes.

Objective: Test your hypothesis using chi square. Answer

1.80

2/3 Daily Catalyst Pg. 77 Nondisjunction

Unit #7 test Genetics Wednesday, Feb. 3rd

Study guide due test day Blood types lab today Tutoring available!

Unit #8 Energy Mini-test Thursday, Feb.12th

Review packet over Mardi Gras

2/3 Class Business Pg. 76 Chi-Squared

Daily Catalyst Class Business HW review Nondisjunction notes Blood types lab Review time

2/3 Daily Catalyst Pg. 77 Nondisjunction

2/2 HW

1. In a certain species of flowering plant, the red allele R is dominant to the white allele, r. A student carried out a cross between a red flowered plant and a white flowered plant. When planted, the 158 seeds that were produced from the cross matured into 92 plants with red flowers and 66 plants with white flowers. Calculate the chi squared value for the null hypothesis that the red flowered parent was a hybrid for the flower color gene. Give your answer to the nearest tenth.

2/2 HW

1. A genetics engineer was attempting to cross a tiger and a cheetah.  She predicted a phenotypic outcome of the traits she was observing to be in the following ratio: 4 stripes only, 3 spots only, 9 both stripes and spots.  When the cross was performed and she counted the individuals she found 50 with stripes only, 41 with spots only and 85 with both.  According to the Chi-square test, did she get the predicted outcome?

Essential Questions

1. What is nondisjunction? 2. When/why does it happen? 3. What is the result of nondisjunction? 4. How is nondisjunction related to sex-

linked genes?

Note Time

Key Point #1: Nondisjunction occurs when homologous chromosomes fail to separate from one another

Can occur during meiosis AND mitosis Caused by a faulty centromere

Key point #2: One gamete receives two of the same chromosome and the other does not receive any copy!

Results in an abnormal number of chromosomes. Aneuploidy

Trisomy 21

Monosomy and Trisomy

Nondisjunction quiz

1. Define nondisjunction. 2. In what organisms is polyploidy most

common? 3. T/f: nondisjunction cannot occur during

mitosis. If nondisjunction occurs in mitosis, what is the effect of nondisjunction in mitosis?

4. What is the chromosome number of a trisomic zygote?

Nondisjunction quiz

1. Define nondisjunction. Homologous chromosomes do not separate properly in

meiosis. Results are gametes with extra copies of chromosomes.

2. In what organisms is polyploidy most common? Plants 3. T/f: nondisjunction cannot occur during mitosis. If

nondisjunction occurs in mitosis, what is the effect of nondisjunction in mitosis?

False, nondisjunction can occur during mitosis and meiosis. The abnormal number of chromosomes will be transmitted to all cells since cells are exact duplicates.

4. What is the chromosome number of a trisomic zygote? (2n+1)

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