Question

5. A cross is made between a pea plant that has constricted pods (a recessive trait; smooth is dominant) and is heterozygous for seed color (yellow is dominant to green) and a plant that is heterozygous for both pod texture and seed color. Construct a Punnett square that depicts this cross. What are the predicted outcomes of genotypes and phenotypes of the offspring

Answer 1

Answer:

Genotypes:

    - 1/8 SsYY

    - 2/8 SsYy

    - 1/8 ssYY              

    - 2/8 ssYy

    - 1/8 Ssyy

    - 1/8 ssyy

    Phenotypes: 3:3:1:1

   - 3/8 smooth-pod and yellow-seeded (SsYY + SsYy)

   - 3/8 constrict-poded and yellow-seeded (ssYY + ssYy)

   - 1/8 smooth-pod and green-seeded (Ssyy)

   - 1/8 smooth-pod and green-seeded (ssyy)

Explanation:

Available data:

• The two forms of the diallelic gene for pod texture are constricted and smooth.
• The dominant allele S expresses smooth pod
• The recessive allele s expresses constricted pod
• The two forms of the diallelic gene for seed color are yellow and green
• The dominant allele Y expresses Yellow
• The recessive allele y expresses green

Cross: a pea plant that has constricted pods and is heterozygous for seed color with a plant that is heterozygous for both pod texture and seed color.

Parental) ss Yy      x      SsYy

Gametes) sY  sy   sY   sy

                SY  Sy  sY   sy

Punnet square)

                             sY         sy         sY        sy

               SY      SsYY     SsYy    SsYY    SsYy

               Sy       SsYy     Ssyy     SsYy     Ssyy

               sY       ssYY     ssYy     ssYY     ssYy

               sy        ssYy     ssyy      ssYy     ssyy

F1) Genotypes:

    - 2/16 = 1/8 SsYY

    - 4/16 = 2/8 SsYy

    - 2/16 = 1/8 ssYY              

    - 4/16 = 2/4 ssYy

    - 2/16 = 1/8 Ssyy

    - 2/16 = 1/8 ssyy

    Phenotypes:

   - 6/16 = 3/8 smooth-pod and yellow-seeded (SsYY + SsYy)

   - 6/16 = 3/8 constrict-pod and yellow-seeded (ssYY + ssYy)

   - 2/16 = 1/8 smooth-pod and green-seeded (Ssyy)

   - 2/16 = 1/8 smooth-pod and green-seeded (ssyy)