NUCLEIC ACIDS

These contain genetic information that each organism needs in order to know which proteins to make. We will be concerned with the relation of nucleic acids to protein structure. There are an infinite number of possible protein structures and also many different life forms. Each living system must select which proteins to make for its own special needs and also pass on this information to its off-spring.

We will be concerned with structural constraints in nucleic acids which allow for not just the storing of genetic information but also allow the involvement of these acids in the transmission of genetic information from molecule to molecule.

The four nucleotide building blocks for DNA and RNA are made from the following components. These are

phosphoric acid, the pentose sugars ribose and 2- deoxyribose

P R D

and the heterocyclic nitrogenous bases

Pentose - base condensation reactions occur at the no.1 O-H

on the pentoses to the no.1 N-H of pyrimidine bases and the

no.9 N-H of the purine bases.

pentose + base à H2O + nucleoside

will give e. g., the following nucleoside products

Condensation of phosphoric acid with the nucleoside at the pentose no. 5 –OH gives for example the nucleotide

The 4 DNA nucleotides are building blocks that condense to form polynucleotides. The DNA molecule contains millions of nucleotides.

The condensations are

nucleotides à water + polynucleotide

DNA double helix

Processes involving communication of genetic information from molecule to molecule:

Replication, Transcription, and Translation.