Question 1 - Past Year - 3 Mark Questions - Chapter 9 Class 10 - Heredity and Evolution

A green stemmed rose plant denoted by GG and a brown stemmed rose plant denoted by gg are allowed to undergo a cross with each other.

(a) List your observations regarding:

(i) Colour of stem in their F1 progeny

(ii) Percentage of brown stemmed plants in F2 progeny if F1 plants are self pollinated.

(iii) Ratio of GG and Gg in the F2 progeny.

(b) Based on the finding of this cross, what conclusion can be drawn?

Answer:

(a)

(i) 

Green is the dominant trait and in the F ₁ progeny, only the dominant trait is expressed.

The color of the stem in F ₁ progeny will be green .

(ii)

If F ₁ plants are self pollinated, the ratio of brown stemmed plants to green stemmed plants in the F ₂ progeny is 1:3

So, the percentage of brown stemmed plants in the F ₂  progeny is 25%

(iii) Ratio of GG : Gg in the F ₂ progeny is 1:2

(b)

Based on the findings of this cross, it can be concluded that:

• Green stem is a dominant trait.
• Brown stem is a recessive trait.
• Only the dominant trait is expressed in the F ₁ progeny.