Question

Who discover the double helical structure of DNA ??.??.??.

Answer 1

Dear Student


Ans. James Watson and Francis Crick

Watson and crick proposed the model of DNA in 1953. The salient feature of this structure include :-

• DNA has a double helical structure.
• The helix has a diameter of 20 A.
• This helix makes a full turn at every 34 A along its length and contains a stack of ten nucleotides per turn,
• The two strands of double helix run in anti- parallel direction.
• Each DNA is made up of- a pentose sugar, nitrogenous bases, phosphate group.
• The sugar and phosphate make up the backbone while the nitrogenous bases are found in the center that hold the two strands together.
• There are 4 nitrogenous bases Adenine (A), Guanine (G), Cytosine (C), Thymine (T).
• A & G are classified as purines and C& T as pyrimidine.
• The nitrogenous base A always pairs with T and C with G.
• There are two hydrogen bonds between A & T and three hydrogen bonds between G & C.

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