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Heredity and Evolution
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30/11/2020 6:08 pm
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What do you understand by the double-helical structure of DNA? Who proposed this structure?
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30/11/2020 6:10 pm
James Watson and Francis Crick proposed the double helical structure of the DNA. According to this structure,
- DNA molecule consists of two polynucleotide strands forming a double helix. Each helical turn has a length of 3.4nm in which ten nucleotides are present.
- Each polynucleotide strand has a backbone of sugar and phosphate. The nitrogenous base is attached to the sugar.
- The nitrogenous bases of the two strands of a double helix form a pair with the help of hydrogen bonds. Adenine pairs with thymine by two hydrogen bonds, whereas guanine pairs with cytosine by three hydrogen bonds.
- The hydrogen bonds hold the two strands of the helix together.