Introduction :
Mendel (1856-1863) conducted hybridization experiments on garden peas( Pisum sativum). During that period, he chose some characteristics of the peas and conducted some cross-pollination on the pea lines that showed stable trait inheritance and underwent continuous self-pollination.
The two experiments lead to the formulation of Mendel’s laws known as laws of inheritance which are:
(i) Law of Dominance
(ii) Law of Segregation
(iii)Law of Independent Assortment
(i) Law of Dominance
According to this law, in a heterozygous condition, the dominant allele is the one whose traits are expressed over the other allele, and the traits of this dominant allele are called to as dominant traits. Dominant characters are those who appear in the F1 generation of characters. The F2 generation contains recessive traits.
(ii) Law of Segregation
According to this law,
“A dominant allele suppresses recessive allele characters and determines the appearance of the organism. When an organism makes gametes, each gamete receives just one gene copy, which is selected randomly.
or,
“When two traits combine to form a hybrid pair, the two characters do not mix and remain separate from one another. Each gamete receives one of the two alleles during the meiosis of the chromosome.
The homozygous dominant and heterozygous springs show dominant traits, while the homozygous recessive springs exhibit the recessive trait”, which is supported by Mendel’s law of segregation.
(iii)Law of Independent Assortment
It is also known as Mendel’s second law of inheritance,
The law of independent assortment states that ” a pair of traits segregates independently of another pair during gamete formation. As the individual heredity factors assort independently, different traits get equal opportunities to occur together.”
F2 generation ratio : Round-yellow = 9 : Round- green = 3: Wrinkled-yellow = 3: Wrinkled-green = 1
Phenotypic ratio of F2 Generation = 9:3:3:1
F2 generation genotypic ratio: 1:2:2:4:1:2:1:2:1