GIVEN: A true breeding parent with yellow kernels was mated with a true breeding
ID: 188639 • Letter: G
Question
GIVEN: A true breeding parent with yellow kernels was mated with a true breeding parent with purple kernels to produce an F1. The F1 (a dihybrid) which was purple was selfed to produce the F2 kernels you observed.
Phenotype
Number of kernels
Purple
215
Yellow
131
Total
346
B. Predict and test the hypothesis:
1. Propose a plausible genetic rationale by: (Show HOW the expected F2 phenotypic ratio is determined.):
Define the relevant segregating alleles in a short paragraph:(Choose from the three loci (C, R, Y) and their alleles as defined on Lab1.8- 12).
Genotype of P1:Yellow=___________________; Purple= ____________________
Genotype of F1: Purple = __________________
Branch diagram showing F2 results (generalized genotypes, phenotypes and proportions- See App. F; can be hand-drawn)
2. State the hypothesis:
State the Null hypothesis (Ho):
State the Genetic Assumptions:
GIVEN: A true breeding purple parent was crossed to a true breeding yellow parent to produce an F1. The F1(a dihybrid), which was yellow, was selfed to produce the F2 kernels you observed.
Phenotype
Number of kernels
Yellow
50
White
20
Purple
34
Total
104
(/3 pts) B. Predict and test the hypothesis:
1. Propose a plausible genetic rationale by: (Show HOW the expected F2 phenotypic ratio is determined.):
Define the relevant segregating alleles:(Choose from the three loci (C, R, Y) and their alleles as defined on Lab1.8- 12).
Genotype of P1:Purple=__________________; Yellow= ____________________
Genotype of F1: Yellow= __________________
Branch diagram showing F2 results
2. State the hypothesis:
State the Null hypothesis (Ho):
State the Genetic Assumptions:
Phenotype
Number of kernels
Purple
215
Yellow
131
Total
346
Epistatic Gene Interactions of genes affecting kernel color of corn A corn kernel has several components most of which represent the same generation. The structure of a corn kernel is whe shown in Figure 1.4. Pericarp Aleurone Starchy indospèrm mb ryo Figure 1.4 Corn kernel structure (from Ford 2000) Kernel color in corn has been the focus of intense study, hence much is known about the genes involved and how they interact (Chinnici 1999). Corn kernels can be red, purple, yellow or white. The red and purple colors of the kernels are the result of the presence of anthocyanin pigments in the aleurone, whercas the yellow color is the result of carotenoid pigments in the endosperm. White kernels result from the lack of either of these pigments. Purple pigment (anthocyanin) is produced in the aleurone: A colorless outer layer of the corn kernel called the pericarp surrounds the lower layer called the aleurone. In the aleurone, anthocyanin pigments are produced via a biochemical pathway as described in Figure 1.5. Each of the steps in the pathway is catalyzed by enzymes coded for by different structural genes (e.g, Pr, AI). Normal copies of all of these genes/enzymes are needed to ensure that the end product- purple pigment is produced in the aleurone. Mutations in any of these genes will produce different colors, depending where the pathway stalls. For example, a br2/br2 kernel would havo a red aleurone becausc the br2 enzyme would be dysfunctional, thereby preventing the red intermediary from being converted to purple. Pr gene AI gene A2 gene Bzl gene Br2 gene Enzyme Pr catalyzes Enzyme Al catalyzes Enzyme A2 catalyzes Enzyme Bzl catalyzes Enzyme Br2 catalyzes RED PURPLE PRECURSOR COLORLESS!-> COLORLESS2 BRONZE C + R Activates C Inhibits Figure 1.5 Simplified anthocyanin pathway resulting in aleurone pigmentation in corn. (Chinnici, 1999) Labl.8Explanation / Answer
Answer
YYyy. X. PPpp
Gametes Y. y. X. P. p
F1. YP. Yp. yP. yp
In F2. YP. yP
YP. YPYP. YyPP
yP YyPP. yyPP
Probability purple 1 and Yellow. 3/4
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