Question

1.After cross-fertilization of true-breeding tall and dwarf plants, the F1 generation was

self-fertilized. The resultant plants have genotype in the ratio

(a) 1:2:1 (homozygous tall : heterozygous tall : dwarf)

(b) 1:2:1 (heterozygous tall : homozygous tall : dwarf)

(c) 3:1 (tall : dwarf)

(d) 3:1 (dwarf : tall)

2. Which of the following characteristics of pea plants was not used by Mendel in his

experiments?

(a) seed colour

(b) seed shape

(c) pod length

(d) flower position

3. Mendel took _______ contrasting characteristics of pea plants.

(a) eight

(b) seven

(c) six

(d) five

4. If both genotype and phenotype shows the same ratios of 1:2:1 in the F2 generation, it shows

(a) incomplete dominance in monohybrid cross

(b) complete dominance in monohybrid cross​

Answer 1

1. b

2.d

3.a

4.a

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Answer 2

The questions are answered below:

1. The resultant plants have genotype in the ratio (a) 1:2:1 (homozygous tall : heterozygous tall : dwarf)

• True breeding tall and dwarf were cross fertilized.
• Let us say tall plants will possess the allele as TT (since true breeding tall is given) and tt.

The F1 generation will have the following genotypic ratio: (TT × tt)

(Punnett square is drawn to determine the genotypic ratio below.)

              T             T      

t             Tt             Tt

t             Tt             Tt

Thus all the plants will be heterozygous tall in F1 generation with a genotype of Tt.

The F2 generation will have the following genotypic ratio: (Tt × Tt)

              T              t      

T            TT             Tt

t             Tt              tt

Thus, the resulting genotype as can be seen from the above Punnett cross is 1:2:1 = TT : Tt : tt (homozygous tall : heterozygous tall : dwarf). While the phenotypic ratio will be 3 : 1 = Tall : Dwarf

2. The following characteristics of pea plants were not used by Mendel in his experiments: (c) pod length

The characteristics used by Mendel in his experiments comprise stem height, pod shape and colour, flower position and colour, and seed shape and colour.

3. Mendel took (b) seven contrasting characteristics of pea plants.

Seven contrasting characteristics taken by Mendel of pea plants are listed below:

• Stem height - tall or dwarf plant
• Flower colour - violet flowers or white flowers
• Flower position - axial flower or terminal flower
• Pod shape - inflated pod or constricted pod
• Pod colour - green pod or yellow pod
• Seed shape - round seeds or wrinkled seeds
• Seed colour - yellow seeds or green seeds

4. If both genotype and phenotype shows the same ratios of 1:2:1 in the F2 generation, it shows (a) incomplete dominance in a monohybrid cross.

• If the monohybrid cross showed complete dominance, then the phenotype will show a ratio of 3 : 1 = dominant : recessive.
• While in incomplete dominance, the dominant and recessive characters get mixed up and give rise to a new trait altogether. Or they show an intermediate trait.
• Thus, the phenotype ratio for incomplete dominnace will be 1 : 2 : 1 = dominant : intermediate/new : receissive.