explain the mendal experiment to support acquired and inherited charecterstics
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Acquiring characteristics or traits from one generation to the other is nothing but inheritance. Here, both the parents contribute equally to the inheritance of traits. It was Gregor Mendel, known as the Father of Genetics, who conducted immense research and studied this inheritance of traits.
It was with his research on plant breeding and hybridization that he came up with the laws of inheritance in living organisms. He conducted his experiments on pea plants to show the inheritance of traits in living organisms.
He observed the pattern of inheritance from one generation to the other in these plants. And thus he came up with Mendel’s Laws of Inheritance, which can be summarized under the following headings:
●Law of Dominance
●Law of Segregation
●Principle of Independent Assortment.
Mendel’s Experiments
◆Monohybrid Cross
It is the cross between two pea plants which have one pair of contrasting characters. For Example, a cross between a tall pea plant and a short (dwarf) plant. The following diagram explains this in detail.
● Observations & Conclusion
In the first generation (F1), the progeny were tall. There was no medium height plant.
In the second generation (F2), 1/4th of the offspring were short and 3⁄4 were tall.
The Phenotypic ratio in F2 is 3: 1 (3 tall: 1 short)
The Genotypic ratio in F2 – 1: 2: 1 – (TT: Tt: tt)
For a plant to be tall, a single copy of “T” is enough. But if a plant has to be short, both the copies should be “t”
Characters like ‘T’ are the dominant traits as they are expressed and ‘t’ are recessive traits as they remain suppressed.
◆ Dihybrid Cross
It is the cross between two plants which have two pairs of contrasting characters. This takes into consideration alternative traits of two different characters. For example, a cross between one pea plant with round and green seeds and the other pea plant having wrinkled and yellow seeds.
● Observations & Conclusion
The F1 generation is 100% hybrid. When RRyy crosses with rrYY, all were Rr Yy with round and yellow seeds in the first generation. The Round and Yellow seeds are the dominant characters.
In F2, the phenotype ratio is 9:3:3:1. The genotype ratio is a very complex one.
This shows that the genes are inherited independently of each other.
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