Question

(a) Provide genetic explanation for the observation in which the flower colour in F1 generation of snapdragon did not resemble either of the two parents. However, the parental characters reappeared when F1 progenies were selfed. (b) State the three principles of Mendel's law of inheritance.

Answer 1

(a) Snapdragon shows incomplete dominance in the heterozygous condition. It means that the dominant allele is not able to mask the effect of recessive allele completely. This results in the production of a new phenotype. An example is flower colour inheritance in Snapdragon.

Parents: RR (red) * rr (white)

$\downarrow$

F1 generation Rr (pink).

When F1 generation flowers are selfed, segregation of gametes takes place and hence parental characters are seen.

Parents: Rr (pink) * Rr (pink)

$\downarrow$

F2 generation RR (red), Rr (pink), rr (white) in 1: 2: 1 ratio (both genotypic and phenotypic)

(b) Three laws of Mendelian inheritance are:

1. Law of dominance: The allele which is able to express itself even in heterozygous condition is called dominant allele and allele whose effect is being masked by dominant allele is called recessive allele.

2. Law of segregation: The alleles for the gene segregate such that each gamete possesses either allele.

3. Law of independent assortment: The inheritance pattern of one character is independent of the inheritance pattern of the other character.