Question

Define or explain the following terms:

i. Dihybrid ratio

ii. Dihybrid 

iii. F₁ generation

iv. F₂ generation

v. Dominant

vi. Recessive

Answer 1

i. Dihybrid ratio: The phenotypic ratio of different types of offsprings (having different combinations) obtained in F₂ generation of dihybrid cross is called Dihybrid ratio. In all Mendelian crosses, the dihybrid ratio is 9 : 3 : 3 : 1.

ii. Dihybrid: It is heterozygous for two traits and produced in a cross between two parents differing in two pairs of contrasting characters.

iii. F₁ generation: The hybrid individuals obtained by a cross between two pure parents with contrasting characters is called F1 generation or first filial generation.

iv. F₂ generation: The generation of offsprings obtained by selfing of F₁ individuals is called F₂ generation or second filial generation

v. Dominant: The character expressed in F₁ generation is called dominant character.

OR

It is an allele that expresses even in presence of an alternative allele.

vi. Recessive: The character which is not expressed in F₁ generation is called recessive character.

OR

It is an allele which is not expressed in presence of an alternative allele.