Question
Explain the Watson and Crick model of DNA.
✓
Answer
Watson and Crick model of DNA:
DNA molecules consist of two polynucleotide chains. These chains form a double helix. Structure, with two strands, which run anti-parallel to one another. Nitrogenous bases in the centre are linked to sugar – phosphate units, which form the backbone of the DNA. Pairing between the nitrogenous bases is very specific and is always between purine and pyrimidine linked by hydrogen bonds.
DNA molecules consist of two polynucleotide chains. These chains form a double helix. Structure, with two strands, which run anti-parallel to one another. Nitrogenous bases in the centre are linked to sugar – phosphate units, which form the backbone of the DNA. Pairing between the nitrogenous bases is very specific and is always between purine and pyrimidine linked by hydrogen bonds.
Adenine [A] links Thymine [T] with two hydrogen bonds (A = T)
Cytosine [C] links Guanine [G] with three hydrogen bonds (C = G). This is called complementary base pairing.
Hydrogen bonds between the nitrogenous bases make the DNA molecule stable.
Each turn of the double helix is 34 A° (3.4 nm). There are ten base pairs in a complete turn.
Nucleotides in a helix are joined together by phosphodiester bonds.
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