Question

DNA: What are the 3 components of a NUCLEOTIDE? What is meant by specific base-pairing in DNA? Why type of bond holds bases together?

Answer 1

Nucleotide is the basic unit of nucleic acids

The three components of nucleotide are:

1. Phosphate group
2. Nitrogen base: Nitrogen bases in DNA are Adenine (A), Guanine (G), Cytosine (C) and Thymine (T)
3. Sugar unit: Deoxyribose in DNA

Specific base pairing in DNA:

• Specific base pairing was hypothesized by Chargaff. Chargaff rule states that Guanine bonds with Cytosine (G=C) and Adenine bonds with Thymine (A=T).
• Specific Base pairing rule states that number of purines (Adenine, Guanine) and pyrimidines (Cytosine and Thymine) are equal in the ratio of 1:1.
• The relative amount of nitrogen bases varies from organism to organism.

Type of bonds holding together Nitrogen bases are: Hydrogen bonds

There are three hydrogen bonds that hold up Guanine and cytosine (G=C) while,

Two hydrogen bonds hold together Cytosine and Thymine (A=T) (A=U*, *Uracil in place of thymine for RNA)