In: Biology
Part A: Punnett Squares
I. Monohybrid Crosses
1. In pea plants yellow peas (A) are dominant to green peas (a). Show a cross between two heterozygous yellow pea plants (Aa x Aa).
A |
a |
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A |
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a |
What is the genotypic ratio of the offspring? _______ AA : _______ Aa: _________ aa
What is the phenotypic ratio of the offspring? _______ Yellow: ________ Green
Part B: Using the Chi-square (χ2) analysis
9. In Parent 1 (P1) corn plants, the color purple is dominant to yellow, and round shape is dominant to wrinkled, which is why both Filial (F1) generation corn plants have the purple and round phenotypes, even when one of the parents (P1) is yellow and wrinkled.
The cross below (F1 x F1) produced the F2 generation corn that you are seeing in Figure 1. Determine the phenotypic ratios of the offspring of this cross: A cross between two F1 generation (heterozygous purple and heterozygous round) corn plants.
Phenotypic Ratio: _____: _____:_____:_____ (This is your hypothesis: The corn in Figure 1 has this ratio.)
PR |
Pr |
pR |
pr |
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PR |
PPRR |
PPRr |
PpRR |
PpRr |
Pr |
PPRr |
PPrr |
PpRr |
Pprr |
pR |
PpRR |
PpRr |
ppRR |
ppRr |
pr |
PpRr |
Pprr |
ppRr |
pprr |
Ans1 : Genotypic ratio of the offspring : 1 :2 : 1
AA : 1 , Aa : 2 , aa : 1
Phenotypic ratio of the offspring : 3 : 1
Yellow : 3 , Green : 1
Explanation :
Ans 9. The phenotypic ratio for the given dihybrid cross is : 9 : 3 : 3 : 1
i.e. there are 9 Purple-Round, 3 Purple-Wrinkled, 3 Yellow-Round and 1 Yellow-Wrinkled seeds.
Explanation :
This is because, dominant allele is expressed over a recessive alle in a heterozygous pair of alleles.