CUET UG Biology Comprehension 2

Monohybrid

The inheritance of flower colour in the dog flower (Snapdragon of Antirrhinum sp) can be understood by crossbreeding between true breeding red-flowered (RR) and true breeding white flowered plants(rr). When they crossed F1(Rr) was pink. When F1 was self pollinated, the F2 results were Red, Pink and White. Here the genotype ratios were exactly as expected, but the phenotype ratios were exactly as expected, but the phenotype ratios have been changed. What happened was that R was not completely dominant over r and this made it possible to distinguish Rr as pink form RR (Red) and rr(white).

1. What was the expected phenotypic ratio in any Mendelian monohybrid cross that had changed when F1 (Rr) was self-pollinated in this cross?

a)1:1

b)1:2:1

c)3:1

d)1:3

2. What will be the phenotypic ratio in F2 generation when F1(Rr) was self pollinated?

a)1:1

b)1:2:1

c)3:1

d)1:3

3. In the above passage, the inheritance is an example of 

a)co-dominance

b)dominance

c)incomplete dominance

d)recessive trait

4. What will be the genotypic ratio in F2 generation when F1(Rr) was self pollinated?

a) 3:1

b) 2:1:1

c) 1:1

d) 1:2:1

5. What will be the percentage of progeny in F1 generation when RR(red flowered plant) is crossed with rr (white flowered plant) in the above passage?

a) 100%Rr

b) 75% RR and 25%rr

c) 25%RR, 50% Rr and 25%rr

d) 25% RR and 75%rr

Answers:

1. c)3:1

2. b)1:2:1

3.c)incomplete dominance

4. d) 1:2:1

5. a) 100%Rr