ICSE 2018: A pea plant which is homozygous for Green pods which are inflated [GGII] is crossed with a homozygous plant for yellow pods which are constricted [ggii]

ICSE 2018:

Q. A pea plant which is homozygous for Green pods which are inflated [GGII] is crossed with a homozygous plant for yellow pods which are constricted [ggii]. Answer the following questions: [5 marks] 

(i) Give the phenotype and genotype of the F1 generation. Which type of pollination has occurred to produce F1 generation? 

(ii) Write the phenotypic ratio of the F1 generation. 

(iii) Write the possible combination of the gametes that can be obtained if two F1 hybrid plants are crossed. 

(iv) State Mendel’s law of ‘Segregation of Gametes’. 

(v) What is the scientific name of the plant which Mendel used for this experiment on inheritance?

Solution:

This 5 marks question based on the concept of Dihybrid cross and Mendel's Law of Segregation and was asked by ICSE board in the year 2018 in SECTION-II. 

The question tested the knowledge of students on the: 

• What is Dihybrid cross?
• Phenotype and Genotype of F1 generation and F2 generation in Dihybrid cross
• Explain Mendel's law of segregation

Let's begin with solving the above mentioned questions:

(i) The phenotype and genotype of F1 generation:

Phenotype: Green Inflated pods

Genotype: GgIi

Cross-pollination has occurred to produce F1 generation

(ii) Phenotypic ratio of F1 generation = 9:3:3:1

(iii) If two F1 hybrid plants are crossed, the gamete combination obtained will be: GI, Gi, gI, gi

(iv) Mendel's Law of Segregation states that "When a pair of allelomorphs (contrasting characters) are brought together in the hybrid (F1 progeny), they remain together in the hybrid without blending but separate complete and pure during gamete formation".

(v) The scientific name of the plant which Mendel used for this experiment on inheritance is Pisum sativum.

Suggested Readings:

• Mendel's Law of Segregation or Law of Purity of Gametes