DNA as genetic material-DNA (Deoxyribo nucleic acid )and RNA (Ribonucleic acid )are two major types of nucleic acid found in cells .Chemical composition of nucleic acids ....Sugar ;phosphate group;and Nitrogen bases .
Pentose sugar + Nitogen Base = Nucleoside
Pentose sugar + Nitrogen Base + Phosphate = Nucleotide
STUCTURE OF DNA -----
According to Watson and Crick