(good +ve test).

- DNA is the basic genetic material contained in all living cells (human, animal, plants, fungi, bacteria and viruses). It is a structure that guides the cell in its production of proteins.

It is the material of which the chromosomes are made. It is double helix twisted strings tightly wrapped into chromosomes.

Structure of DNA:

DNA is formed of sugar-phosphate backbone consists of units named as nucleosides, to each one a nitrogenous base is attached forming nucleotides. There are four nitrogenous bases of the DNA that are arranged in pairs [Adenine (A) pairs with thymine (T), while cytosine (C) pairs with guanine (G)] in a particular order (the DNA sequence), encoding all genetic instructions for an organism. The two DNA strands are held together by hydrogen bonds between the bases.

• Human DNA is formed of about 3 billion of base pairs arranged in triple (codons), each code for certain amino acid.

• A strand of DNA contains genes, areas that regulate genes, and areas that either have no function, or a function yet unknown

• The genetic code that determines the individual characteristics depends on the sequence of bases on DNA molecule that is extremely different in every individual except in identical twins.

DNA Under an electron microscope

Category: Forensic Medicine Notes