Nucleoside and nucleotide

Nucleoside and nucleotide The nitrogenous base is chemically linked to one molecule of sugar (at the -carbon of the sugar) forming a nucleoside . When a phosphate group is attached to the ' carbon of the same sugar, the nucleoside becomes a nucleotide . The nucleotides are joined (polymerized) by condensation reaction to form a polynucleotide chain. The hydroxyl group on the ' carbon of a sugar of one nucleotide forms an ester with the phosphate of another nucleotide. The chemical bonds that link the sugar The differential labelling thus enabled them to identify DNA and proteins of the phage. Hershey and Chalse mixed the labelled phages with unlabelled E. coli and allowed bacteriophages to attack and inject their genetic material. Soon after infection (before lysis of bacteria), the bacterial cells were gently agitated in a blender to loosen the adhering phase particles. It was observed that only P was found associated with bacterial cells and S was in the surrounding medium and not in the bacterial cells. When phage progeny was studied for radioactivity, it was found that it carried only P and not S (Fig. . ) . These results clearly indicate that only DNA and not protein coat entered the bacterial cells. Hershey and Chase thus conclusively proved that it was DNA, not protein, which carries the hereditary information from virus to bacteria.