Some Aspects of Nucleic Acids::=-
Nucleic acid were first demonstrated in the nuclei of pus cell in 1868 and in sperm head in 1872 by a Swedish doctor Friedrich Miescherand named as nuclein. Nucleic acid is present in every living cell as well as in vieuses and have been found to be the essential substance of the genes and the apparatus by which the genes act. Two type of nucleic acid have been found; these are 1. Deoxyribonucleic acid, i.e. DNA and 2. Ribonucleic acid, i.e. RNA.
DNA is a long thin polymer and contains in its structure the blueprints or the master plans for the normal growth and development of each and every living organism. DNA is responsible for the two fundamental properties which are common to all living organism; these are (1) ability to produce their kind or in modern scientific language to store, express and transmit genetic information (or instruction) and (2) to undergo mutation. In eukaryotic cell’s DNA occurs in combination with protein forming nucleoproteins; the protein part is represented chiefly by histones of several types and also non-histone chromosomal protein. Histones of small, highly basic protein. They have amino acid sequences that are the most conserved known. An eukaryote is unicellular or multicellular organism with cell having a membrane-bounded nucleus; in addition they have multiple chromosomes and internal organelles. Histones are not associated with prokaryotic DNA. The nucleoprotein was so named because they make a large part of the nuclear material of the cell. However nucleoprotein are also found in the cytoplasm associated particularly with the ribosome, when the RNA is intimately concerned with the synthesis of protein.
RNA unlike DNA is of more than one type, i.e. messenger RNA ribosomal RNA and transfer RNA also called soluble RNA, i.e. sRNA. RNA molucle bring about reaction under direction from DNA; however some RNAs also possess enzymatic function and in some cases represents the genome instead of the DNA as inRNA viruses.
- Genes of eukaryotes are present in chromatin which is made up of proteins and DNA along with some RNA. The chromatin is called, as it can be stained by a number of stains. Some of the chromatin contain about equal amounts of DNA and protein. Some of the chromatin RNA is messenger RNA being formed, but some of it appear to be associated with chromosome function. Under the electron microscope chromatin shows dense spherical particle called nucleosome. Nucleosomes are composed of DNA wound around a collection of histone molecule. it has been established that with a expectation it is the DNA, which is the carrier of genetic information in all organism.
- Mutation is primarily changes in the structure of DNA. Mutation is essential for evolution of new varitiesandv species.
Many mutations are lethal and produce disease. The process of evolution continues. In case of higher animals it may not be possible to note any mutation during any one’s times their breeding is slow. But in the case of bacterial cell e.g. E.coli a single bacterium gives rise to billion daughter cells in 24 hours; this allows us to witness evolution in the laboratory.