IT2EDU Empowering Education Through Technology
Related Articles
EVOLUTION OF GENETICS
The most acceptable work in Genetics has been done by Gregor Johann Mendel. Mendel was born in a peasant family, in the later years of his life, he became monk. He conducted experiments on the pea plants in his monastery, which lead to important conclusions. Thus, he is known as the FATHER OF GENETICS.
PRE-MENDELIAN WORK ON GENETICS
Earlier scientists, Hippocrates and Aristotle laid the first step in the field of Genetics prior to Mendel’s work. Hippocrates suggested that every individual possessed gemmules, these migrate to the gonads and contribute in the formation of embryo, which divides further to form an individual. However, Aristotle had a belief that semen and menstrual blood mix together to form an embryo, later by division it grows in size and forms a complete individual. They both believed in the theory of Inheritance of Acquired Characters, however, a serious rejection was given to their thought when Weismann gave his germplasm theory. He elaborated his theory as, only those characters are passed from one generation to another which are present in the germplasm, he cutted the tail of the rat and observed the morphology of rat for many generations, no rat was observed without tail by him, which made his findings true.
MENDELIAN WORK ON GENETICS
Gregor Johann Mendel conducted his experiments on the garden pea, Pisum sativum. He chose seven contrasting traits in Pea. The chosen traits were-
- Plant height.
- Flower color.
- Flower position.
- Pod color.
- Pod shape.
- Seed color.
- Seed shape.
Every trait existed in 2 forms- dominant and recessive. Pea flowers naturally exhibited self-pollination, but he made them to undergo cross pollination by artificial hybridization. He initiated his experiment by taking one character at a time. His findings were, in the first generation (obtained after crossing 2 parents) or F1 generation, only the dominant trait appears. This was also known as Law of Dominance. Selfing of F1 yields F2 generation that showed the appearance of both dominant and recessive forms. He explained Law of segregation using monohybrid cross and Law of Independent Assortment using dihybrid cross. Mendel gave genotypic and phenotypic ratio for both monohybrid and dihybrid crosses. Mendel was known as the Father of genetics, he never knew about his marvelous achievements when he was alive.
Later, after his death, rework was done on his discoveries by Hugo De Vries, Correns and Tschermark. They found that certain plants, Mirabilis jalapa and Antirrhinum majus were exceptions to incomplete dominance, these flowers in their F1 generation, showed the appearance of both the characters.
Further, chromosomes were discovered by Nageli and it was concluded that genes are present on the chromosomes and they are passed from one generation to another. Mendel was never aware of chromosomes as he used the word factor to denote the genes.
Morgan prepared the first chromosomal map by dong experiments on Drosophila melanogaster.
After few years, Watson and Crick discovered the double helical structure of DNA. They were awarded Nobel Prize for their discovery. Later, central dogma of molecular biology was discovered. According to central dogma, DNA led to the synthesis RNA (transcription), the latter lead to the synthesis of proteins which is also known as translation. However, in certain viruses reversal of central dogma occurs as DNA is not a hereditary material in them. Such viruses are known as retroviruses.
Griffith’s work on Staphylococcus pneumonia and reformulation of that work by Avery, Mac Leod and Mac Carty proved that DNA acts as a genetic material, and this passes from one generation to another, carrying hereditary traits
The work of these scientists has laid important stepping stone in the field of Molecular Genetics.
