Genetics and Evolution Notes for MH-CET / NEET 2014

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Genetics and Evolution Notes for MH-CET / NEET 2014

  1. 1. Genetics and Evolution Heridity and variation: ∙ All living organisms possess remarkable characteristic i.e. reproduction. ∙ During the process they inherit the characters to their offsprings. Heredity Heredity is transmission of characters from one generation to the next or from parents to their offsprings. Variations Variations are differences between the parents and offsprings, among the offsprings of same parents and among the individuals of the same species. ∙ Genetics is the branch of biology which deals with heredity and variations. The term genetics was given by Bateson in 1906. ∙ The first scientific explanation to the process of inheritance was given by Gregor
  2. 2. Mendel in 1866 He performed number of experiments on garden pea and proposed laws which are known as Mendel’s laws of inheritance and his work is known as Mendelism. He is rightly called as ‘Father of Genetics’. Mendelian Inheritance 1. Organisms which are the result of asexual reproduction are identical to their parents and can be called as clones. Organisms produced by sexual reproduction are not identical to either of their parents but shows some characters of both the parents. They are called as offsprings. 2. Mendel suggested that characters are passed on from one generation to the next through some particles which he called as factors. Mendel’s Experiments Selection of material Mendel selected pisumsativum L for his experiments because of following characters:
  3. 3. 1. Garden pea is annual plant with short life span of three to four months. 2. It is small herbaceous plant that produces many seeds. 3. In nature it is self pollinated and artificial cross pollination is also easy. 4. Flowers are large for easy emasculator essential in artificial cross and produce fertile offsprings. 5. The plant was available with many varieties showing the contrasting characters. There were no intermediate characters. Selection of characters Mendel selectedseven different characters. Each character exists in two distinct contrasting forms. These characters were – 1. Stem height (tall and dwarf) 2. Seed colour (yellow and green) 3. Seed shape (round and wrinkled) 4. Pod colour (green and yellow) 5. Pod shape (inflated and constricted) 6. Position of flower (auxillary and terminal). 7. Flower colour (coloured and white)
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