AN OVERVIEW OF NUCLEIC-ACIDS AND GENE-REGULATION

The genetic information for the development of an organism is stored a nd inherited by deoxyribonucleic acid (DNA). In higher organisms the D NA is located within the cell nucleus. DNA has the structure of a doub le helix and contains a specific sequence of four types of nucleotides that are specified by the bases adenine, guanine, cytosine and thymin e. Replication of the DNA double helix by DNA polymerase results in th e formation of two double helices with identical nucleotide sequences. Expression of the information contained in the DNA requires the synth esis of ribonucleic acid (RNA) copies and subsequent transport of the RNA from the nucleus to the cytoplasm. One type of RNA, called messeng er RNA (mRNA), contains the instruction for the amino acid sequence of polypeptides. The translation of the nucleotide sequence of mRNA into the amino acid sequence of polypeptides is facilitated by ribosomes. For the synthesis of each of the different kinds of polypeptides a spe cific mRNA is expressed. The expression of the genetic information is mainly regulated by direct interactions of control elements located on DNA and RNA with certain protein factors.