MOLECULAR GENETICS

THE NUCLEIC ACIDS

First isolated by Friedrich Miescher in 1869.
He isolated what he called nuclein from the nuclei of pus cells.
Nuclein was shown to have acidic properties, hence it became called nucleic acid.

Two types of nucleic acid are found

• Deoxyribonucleic acid (DNA)

• Ribonucleic acid (RNA)

The distribution of nucleic acids in the eukaryotic cell is interesting

DNA is found in the nucleus with small amounts in mitochondria and chloroplasts.

RNA is found throughout the cell.

DNA as genetic material: The circumstantial evidence

1. It is present in all cells and virtually restricted to the nucleus.
   
    

2. The amount of DNA in somatic cells (body cells) of any given species is constant (like the number of chromosomes). The RNA content varies a lot.
   
    

3. The DNA content of gametes (sex cells) is half that of somatic cells. In cases of polyploidy (multiple sets of chromosomes) the DNA content increases by a proportional factor.
   
    

4. The mutagenic effect of UV light peaks at 253.7nm. This is the peak for the absorption of UV light be DNA.

NUCLEIC ACID STRUCTURE

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© Paul Billiet 2009