Question

One character Gregor Mendel studied was pea pod colour where the allele for green pods was dominant and the allele for yellow pods was recessive. A second character he studied was pea pod shape where the allele for inflated was dominant and the allele for constricted was recessive. In crossing these plants he started with one true-breeding parent that had green inflated pods and the other true breeding parent had yellow constricted pods.

1. a) What is the genotype of the P generation?

2. b) What is the genotype of the hybrid F1 generation?

3. c) Construct a punnet square to show the possible combinations of alleles in the F2

   generation

4. d) What is the genotypic ratio in the F2 generation?

5. e) What is the phenotypic ratio in the F2 generation?

Answer 1

ANSWER- True-breeding  parent that had green inflated pods and the other true breeding parent had yellow constricted pods are crossed together. When the cross is made for two characters then the cross is called dihybrid cross.

• Genotype is the genetic constitution of an organism while phenotype is defined as the physical appearance of a trait which is visible.
• Let the pea pod colour is represented by G letter and pea pod shape is represented by I.Green and inflated pea pods traits are dominant while yellow and constricted pea pods are recessive trait and for the expression of dominant trait , one allele is sufficient while for recessive trait , both the alleles of a gene are required.

• a) Genotype of parent generation is GGII for green inflated pods and ggii for  yellow constricted pods.
• b) Genotype of the hybrid F1 generation is GgIi.
• c) Punette square is shown in the image attached below showing all possible combinations of alleles of F2 generation.
• d) Genotypic ratio in F2 generation is shown in the image attached.
• e) Phenotypic ratio in F2  generation is shown in the image attached.

A compelete dihybrid is shown in the image attached starting from parent generation to F2 generation.