Today is: 
10 December 2018 
 

DNA

 

Issue 6 - April 2013

Now that we know many facts about genetics and every high school student knows the exact structure and function of DNA, it is hard to believe that it was only in the second half of the 19th century, after 4 billion years of life on earth, that anybody knew the DNA molecule even existed. An article published in the journal ‘Nature’ 60 years ago briefly discussed the double helix structure of the DNA molecule and suggested that the two strands of DNA allowed it to create identical copies of itself. This announcement by Watson and Crick changed the world of medicine and science forever. From the time that George Mendel discovered the fundamental laws of inheritance in the 19th century it took several decades of effort by more than 20 scientists to bring us to the point of discovering the complicated structure, function and replication characteristics of the DNA molecule as we know it today. DNA is the hereditary molecule in humans and all other living organisms and viruses, packaged in bundles called chromosomes, located in the cell nucleus, as well as small amounts in mitochondria and chloroplasts (other cell components). The DNA molecule is the information storage (genetic characterisation) for anything which contributes to a living cell; the shape, the form, the size, the function, what the cell produces, how it is produced etc. Segments of the DNA molecule which carry this specific information are called genes. Each DNA molecule has a unique set of genes called genotype. Each gene has a unique specification which influences particular characteristics in an individual which is called phenotype. Although the completion of the human gene sequences (genome) was celebrated in April 2003, and it would appear that sequencing of the human chromosomes is officially finished, the exact number of human genes is still unknown. All living organisms inherit their traits from their parents through the genes. Genetics is the science of genes, where molecular structure, function, behaviour and distribution of genes are analysed. Although genetics plays a large role in an organism’s behaviour, what is experienced by an organism after inception such as nutrition and health also has a large effect. Genetic engineering is another branch in this field of science where genes are manipulated by using biotechnology to create genetically modified organisms in order to alter or improve their function for medical, industrial, agricultural and research purposes. The effect of the DNA genes is translated through the transcription of another molecule named RNA (Ribonucleic acid) which will be then responsible for making specific proteins. Each of these proteins is responsible for a unique action. Gene prediction programs estimate a total of 20000 protein encoding genes for the human genome. Only 1.5% of the human genome has a protein coding role and some DNA sequences that do not code protein may still encode functional non-coding RNA molecules, which are involved in the regulation of gene expression. The exact role of the other 50% of the human genome is still a long standing puzzle to scientists. We still have a long way to go! • ... read more