In watermelosn, bitter fruit [B] is dominant over sweet fruit (b), and yellow sp

Question

In watermelosn, bitter fruit [B] is dominant over sweet fruit (b), and yellow spots {S} are dominant over no spots (s). The genes for these two characteristics assort independently. A homozygous plant that has bitter fruit and yellow spots is crossed with a homozygous plant that has sweet fruit and no spots. The F1 are intercrossed to produce the F2.

1. What will be the phenotypic ratios in the F2?

2. If an F1 plant is backcrossed with the bitter, yellow-spotted parent, what phenotypes and proportions are expected in the offspring?

3. If an F1 plant is backcrossed with the sweet, nonspotted parent, what phenotypes and proportions are expected in the offspring?

Explanation / Answer

BBSS

1/16

Bitter and Yellow spots

BbSs

1/16

Bitter and Yellow spots

BbSs

1/16

Bitter and yellow spots

Bb SS

1/16

Bitter and Yellow spots

BBSs

1/16

Bitter and Yellow spots

BBss

1/16

Bitter and no spots

BbSs
1/16

Bitter and no spots

Bb Ss

Bitter and Yellow spots

BbSs

1/16

Bitter and Yellow spots

BbSs
1/16

Bitter and no spots

bbss

1/16

Sweet and no spots

bbSs

Sweet and yellow spots

BbSS

1/16

Bitter and Yellow spots

BbSs

Bitter and Yellow spots

bbSs

Sweet and Yellow spots

bbSS

Sweet and Yellow spots

9:3:3:1 The mendelian ratio of inheritance

9 Bitter and Yellow spots

3 Bitter and no spots

3 Sweet and Yellow spots

1 Sweet and no spots

1. What will be the Phoenix pic ratios in the FE?

Answer.

P: homozygous bitter fruit, yellow spots (BBSS) × homozygous sweet fruit and no spots (bbss)

F1: All progeny have bitter fruit and yellow spots (BbSs)

The F1 are intercrossed to produce the F2: BbSs × BbSs

The F2 phenotypic ratios are as follows:

9/16 Bitter fruit and yellow spots

3/16 Bitter fruit and no spots

3/16 Sweet fruit and yellow spots

1/16 Sweet fruit and no spots.

2. If an F1 plant is backcrossed with the bitter, yellow-spotted parent, what phenotypes and proportions are expected in the offspring?

Answer.The backcross of a F1 plant (BbSs) with the bitter, yellow-spotted parent will produce all bitter, yellow-spotted offspring.

3.  If an F1 plant is backcrossed with the sweet, nonspotted parent, what phenotypes and proportions are expected in the offspring?

Answer. The backcross of a F1 plant (BbSs) with the sweet, non-spotted parent (bbss) will produce the following phenotypic proportions in the offspring:

¼ Bitter fruit and yellow spots (BS)

¼ Bitter fruit and no spots (Bs)

¼ Sweet fruit and yellow spots (bS)

¼ Sweet fruit and no spots (bs)

BS1/4 Bs1/4 bs 1/4 bS 1/4 BS 1/4

BBSS

1/16

Bitter and Yellow spots

BbSs

1/16

Bitter and Yellow spots

BbSs

1/16

Bitter and yellow spots

Bb SS

1/16

Bitter and Yellow spots

Bs 1/4

BBSs

1/16

Bitter and Yellow spots

BBss

1/16

Bitter and no spots

BbSs
1/16

Bitter and no spots

Bb Ss

Bitter and Yellow spots

bs1/4

BbSs

1/16

Bitter and Yellow spots

BbSs
1/16

Bitter and no spots

bbss

1/16

Sweet and no spots

bbSs

Sweet and yellow spots

bS 1/4

BbSS

1/16

Bitter and Yellow spots

BbSs

Bitter and Yellow spots

bbSs

Sweet and Yellow spots

bbSS

Sweet and Yellow spots

9:3:3:1 The mendelian ratio of inheritance

9 Bitter and Yellow spots

3 Bitter and no spots

3 Sweet and Yellow spots

1 Sweet and no spots

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