COMPOSITION OF BLOOD
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WATSON AND CRICKS MODEL OF DNA
biologicalinform.blogspot.com WATSON AND CRICKS MODEL OF DNA The double stranded helical structure of DNA was proposed for the first time by James Watson and Francis Crick in 1953. In Eukaryotic, DNA molecule is present in each chromosomes if nucleus. The two strands of DNA molecule are spirally twisted around each other as well as a central axis to form tight handed double helix. The coiling of two strand is plectonemic i.e. the two strands can’t be easily separated from each other. The backbone of strand is formed by alternately arranged Deoxyribose sugar and phosphate molecular which are joined together by Phosphodiester bonds . Each strand is long polypeptide chain composed of many basic units or monomers known as Deoxyribonucleotides, hence called polymer compounds. Each transverse step is made up of nitrogen bases which are purines and pyrimidines. Nitrogen bade is attached horizontally at carbon number one of Deoxyribose sugars. The nitrogen bases of two DN
Monohybrid cross Andmonohybrid ratio :- Def : A cross between two pure (homozygous) parents having a single pair of contrasting characters is used or studied is called as monohybrid cross, and ratio obtained from monohybrid cross is called as monohybrid ratio. (Phenotypic ratio = 3:1 & Genotypic ratio = 1;2;1 ) This experiment involving 3 steps - In first step (I) - Mendel selected pure tall pea plant as a female parent and pure Dwarf pea plant as a male parent. He confirmed whether they are true breeding or not by selfing them for three generations. In step second (II) - Mendel performed artificial cross between female and male parent which were Tall & Dwarf. Mendel expecting progeny obtained from parent will be intermediate height or 50 % Tall & 50% dwarf but he surprised and found all were Tall in F 1 generation (Tt). He started thinking, where the dwarfness has gone? Why and how it got eliminated ? He thinked,
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