The cross between two garden pea plants with a pair of contrasting characters is called ________.

The cross between two garden pea plants with a pair of contrasting characters is called monohybrid cross.

In mendelian monohybrid cross, phenotypic ratio of F₂ generation is ______.

External characters of any organism such as tallness and dwarfness are called phenotypes, and the ratio of these characters is called phenotypic ratio. In the F₂ generation of monohybrid cross between garden pea plants, 3 plants were tall and 1 plant was dwarf. Hence the phenotypic ratio of F₂ generation in monohybrid cross is 3 : 1.

The garden pea plant having yellow coloured seeds was crossed with the garden pea plant having green coloured seeds and F₁ generation was produced. All plants of F₁ generation were having yellow coloured seeds. What does this mean?

The F₁ generation produced by the cross of plant having yellow seed colour and plant having green seed colour, will have different allele for seed colour. The trait that gets expressed is called the Dominant trait while the trait that is not expressed is called the recessive trait. In F₁ generation, all plants were having yellow coloured seeds. It means that the trait of yellow seed colour is expressed and green seed colour is not expressed. Hence yellow seed colour is dominant over green seed colour and green seed colour is the recessive trait. Hence option 4 is the right answer.

Which one of the following can not be explained on the basis of law of dominance?

According to Mendel's law of dominance, in every individual the characters are controlled by factors. Due to the involvement of two parents in sexual reproduction, factors are found in pairs. The allele in the pair of factors may be similar or different. In the pair of factors, if the two alleles are different then only one of the factors is expressed. The factor that gets expressed is called the Dominant factor/ dominant gene, while the factor that is not expressed is called the recessive trait/recessive gene. Hence option 1, option 2 and option 3 can be explained on the basis of law of dominance. Alleles do not show any blending and the characters of both parents are recovered in F₂ generation can be explained on the basis of law of segregation.

In mendelian monohybrid cross, genotypic ratio of F₂ generation is ______.

The factors or traits that regulate the traits are called genotypes. In the F₂ generation of monohybrid cross between garden pea plants is TT:Tt:Tt:tt i.e. 1:2:1.

A homozygous tall garden pea plant is crossed with homozygous dwarf garden pea plant and F₁ generation is produced. Then F₁ hybrid plant is crossed with the homozygous dwarf garden pea plant. The progeny produced by this cross will contain:

Homozygous tall garden pea plant will be of genotype TT. Homozygous dwarf garden pea plant will be of genotype tt. So the plant of F₁ generation will be of genotype Tt. The character of tallness is dominant and the dwarfness is recessive. Hence in F₁ generation the garden pea plant will be tall. After that the F₁ generation garden pea plant (Tt) is crossed with homozygous dwarf garden pea plant (tt). So the progeny produced by this cross will contain 50% tall plants of genotype (Tt) and 50% dwarf plants of genotype (tt).