Question

punnett squares: incomplete dominance
a farmer wants to grow some pink flower color flowers to sell next spring for bouquets. he crosses a red flower plant with a white flower plant. in four oclock flower plants, the red color allele is incompletely dominant (or partially dominant) over the white allele.
complete the cross on the right
allele notation key:
red allele r white allele r
red flower plant × white flower plant
1 phenotype ____ 4 phenotype ____
2 genotype ____ 5 genotype ____
3 allele(s) ____ 6 allele(s) ____
7 punnett square
(put the same alleles from each parents alleles)

1. what is the genotype ratio of the offspring plants? ______
2. what is the phenotype ratio of the offspring plants? ______

the farmer then crosses two of the pink flower plants from the above cross. what will the genotype and phenotype ratios be in the offspring?
complete the cross on the right
allele notation key:
red allele r white allele r
pink flower plant × pink flower plant
g phenotype ____ h phenotype ____
i genotype ____ j genotype ____
k allele(s) ____ l allele(s) ____
16 punnett square
(put the same alleles from each parents alleles)

1. what is the genotype ratio of the offspring plants? ______
2. what is the phenotype ratio of the offspring plants? ______

the farmer then crosses one red flower plant to a pink flower plant. what will the genotype and phenotype ratios be in the offspring?
allele notation key:
red allele r white allele r
pink flower plant × red flower plant
19 phenotype ____ 22 phenotype ____
20 genotype ____ 23 genotype ____
21 allele(s) ____ 24 allele(s) ____
25 punnett square
(put the same alleles from each parents alleles)

1. what is the genotype ratio of the offspring plants? ______
2. what is the phenotype ratio of the offspring plants? ______

Explanation:

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First Cross: Red × White

Step1: Identify red plant traits

Phenotype: Red Flower
Genotype: $RR$
Alleles: $R, R$

Step2: Identify white plant traits

Phenotype: White Flower
Genotype: $rr$
Alleles: $r, r$

Step3: Fill Punnett Square

	$R$	$R$
$r$	$Rr$	$Rr$

Step4: Calculate genotype ratio

All offspring are $Rr$, so ratio: $1:0$ (all $Rr$)

Step5: Calculate phenotype ratio

All offspring are pink, so ratio: $1:0$ (all pink)

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Second Cross: Pink × Pink

Step6: Identify pink plant traits

Phenotype: Pink Flower
Genotype: $Rr$
Alleles: $R, r$

Step7: Fill Punnett Square

	$R$	$r$
$r$	$Rr$	$rr$

Step8: Calculate genotype ratio

Count genotypes: $1\ RR : 2\ Rr : 1\ rr$

Step9: Calculate phenotype ratio

Count phenotypes: $1\ \text{Red} : 2\ \text{Pink} : 1\ \text{White}$

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Third Cross: Pink × Red

Step10: Identify parent traits

Pink plant: Phenotype = Pink Flower, Genotype = $Rr$, Alleles = $R, r$
Red plant: Phenotype = Red Flower, Genotype = $RR$, Alleles = $R, R$

Step11: Fill Punnett Square

	$R$	$r$
$R$	$RR$	$Rr$

Step12: Calculate genotype ratio

Count genotypes: $1\ RR : 1\ Rr$

Step13: Calculate phenotype ratio

Count phenotypes: $1\ \text{Red} : 1\ \text{Pink}$

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Answer:

First Cross (Red × White)

1. Phenotype: Red Flower
2. Genotype: $RR$
3. Allele(s): $R, R$
4. Phenotype: White Flower
5. Genotype: $rr$
6. Allele(s): $r, r$
7. Punnett Square (filled as above)
8. Genotype ratio: 1 (all $Rr$)
9. Phenotype ratio: 1 (all pink flowers)

Second Cross (Pink × Pink)

1. Phenotype: Pink Flower
2. Genotype: $Rr$
3. Allele(s): $R, r$
4. Phenotype: Pink Flower
5. Genotype: $Rr$
6. Allele(s): $R, r$
7. Punnett Square (filled as above)
8. Genotype ratio: $1\ RR : 2\ Rr : 1\ rr$
9. Phenotype ratio: $1\ \text{Red} : 2\ \text{Pink} : 1\ \text{White}$

Third Cross (Pink × Red)

1. Phenotype: Pink Flower
2. Genotype: $Rr$
3. Allele(s): $R, r$
4. Phenotype: Red Flower
5. Genotype: $RR$
6. Allele(s): $R, R$
7. Punnett Square (filled as above)
8. Genotype ratio: $1\ RR : 1\ Rr$
9. Phenotype ratio: $1\ \text{Red} : 1\ \text{Pink}$