MENDELS WORK IN GENETICS
In the study of genetics, Gregor Mendel (1866) worked with the garden pea. (Pisumsativum) because of three unique properties present in it. These are
- Peas are self-pollinating
- They have a very short lifespan
- They have several unique genetic characteristics e.g. round or wrinkled seeds, tallness or shortness, seeds /pods/ flowers colouration, pod texture etc.
The Mendel’s methods of studying genetics are two:
- Monohybrid inheritance
- Dihybrid inheritance
Mendel crossed two different plants which differ in one pair of contrasting characters e.g. tall and short plants. The procedures he followed are as follows:
- He planted tall plants for several generations and got all tall plant offspring. Likewise, the short plants he planted yielded all short plant offspring.
- He then planted tall and short plants. When the flowers were produced, he cross pollinated the pollen grains (male gamete) of the tall plant with the stigma (female gamete) of the short plant.
- He then planted the seeds of the cross in the procedure (ii) above and obtained all tall plants. This he called the first filial generation(F1,)
- He then crossed the F1 plants, collected their seeds and sowed them. He got tall and short plant in ratio 3: 1. This he called second filial generation (F2)
This experiment resulted into Mendel’s first law of inheritance which is based on the principle of complete dominance.
Mendel’s first law of inheritance otherwise known as the law of segregation of genes states that paired alleles segregate from each other when the homologous chromosomes on which they reside separate during meiosis. Each gamete receives one of the two alleles. The actual segregation occurs in F2 generation.