Mendel is known as the father of genetics. Mendel’s laws are Law of Dominance, Law of Segregation and Law of Independent Assortment. These laws came into existence from experiments on pea plants with a variety of traits.
In the first experiment, only a single character (plant height) was considered and was known as monohybrid inheritance. Another experiment was based on two characters (seed shape and colour), thus called dihybrid inheritance.
Pea plants experiment
Mendel was successful in showing that traits were inherited independently with the help of pea plants. He chose two different pea plants that had the following traits:
- Pea shape: Round or wrinkled
- Pea colour: Yellow or green
- Flower colour: Purple or white
- Flower position: Terminal or axial
- Plant height: Tall or short
- Pod shape: Inflated or constricted
- Pod colour: Yellow or green
Reason for selection of pea plants
He selected a pea plant for his experiments due to the following reasons
- The pea plant can be easily grown and maintained.
- They are naturally self-pollinating but can also be cross-pollinated.
- It is an annual plant, therefore, many generations can be studied within a short period of time.
- It has several contrasting characters.
Principals derived from Mendel’s experiments
Following are the principles of inheritance that were developed based on Mendel’s experiments:
- Fundamental theory of heredity: According to the theory, offspring have their genes inherited from their parents.
- Principle of segregation: It was studied that during reproduction, the factors determining the traits get separated into reproductive cells and this process is known as meiosis and reunite during fertilization.
- Principle of independent assortment: Different chromosomes have different genes located on them that can be inherited independently of each other.
Therefore, the result of his experiment when he crossed a pea plant with yellow colour, round seed with green colour wrinkled seed were two parental and two recombinant phenotype. The parental were yellow round and green wrinkled. While the recombinant were yellow wrinkled and green round. This result explains that the traits are separate from their parental combinations and are inherited independently.
Determination of Phenotype from dominant and recessive allele
Understanding the traits of twins