describe the structure of DNA molecules
Answers
Explanation:
Each molecule of DNA is a double helix formed from two complementary strands of nucleotides held together by hydrogen bonds between G-C and A-T base pairs. Duplication of the genetic information occurs by the use of one DNA strand as a template for formation of a complementary strand.
Answer:
The structure of DNA molecule was described by Watson and Crick.
This is the most commonly found DNA structure and is also called the B-DNA.
The B-DNA is a double stranded, ladder like right handed helix. One complete turn in the helix is about 34Ao and is made of a major groove and a minor grove. The diameter of the DNA molecule is 20Ao.
The strands run antiparallel to each other and are held together by Hydrogen bonds.
The macromolecule is made of smaller units called the nucleotides.
A nucleotide has three components namely
Phosphate
Deoxyribose sugar
Nitrogen bases.
Phosphate and sugar form the parallel edges of the ladder like stucture, while the Nitrogen bases are attached on the innerside.
The Nirogen bases on the antiparallel strands pair to form the steps of the ladder.
There are four types of Nitrogen bases in a DNA molecule.
Adenine
Guanine
Cytosine
Thymine
The pairing occurs between Nitrogen bases placed opposite to each other on the antiparallel strand in a fixed pattern.
Adenine pairs with Thymine with the help of two Hydrogen bond, while Guanine pairs with Cytosine with the help of three Hydrogen bonds.
The distance between the two adjacent base pairs or steps is 3.4Ao.
