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Wednesday, September 30, 2009

DNA (Short Note)

Wednesday, September 30, 2009 - 1 Comment

DNA is Deoxyribose nucleic acid. It occurs in chromosomes (nuclear reticulum). DNA has deoxyribose with one less oxygen atom in its molecule. DNA is double stranded molecule. Biologists are of view that all secrets of life are embodied in DNA or in other words it is the chemical basis of life. DNA is sole genetic (hereditary) material migrating intact from generation to generation through reproductive units or gametes and is responsible for the development of specific characters of a plant. It also controls the biosynthetic processes of the cell including protein synthesis, Watson and Crick gave model of DNA in 1953 which double stranded structure. Each strand (helix) is a chain of several nucleotides and is known as poly nucleotide chain. Each nucleotide consist of a de oxyribose sugar, one nitrogen base and one molecule of phosphoric acid. Nitrogen bases are adenine, guanine, cytosine and thiamine.

Dicyclic nitrogen bases are purines, therefore adnine and guanine are purines. Monocyclic nitrogen bases like cytosine and thiamine are known as Pyramidines.

Linkage and Crossing Over (Short Note)

According to Conservative estimate there are thousands of genes in four pairs of chromosomes of Drosophila. It means that each chromosome contains large number of genes, similar is the situation in all organisms. The chromosomes behave as single units. All the genes in a given chromosome tend to remain together during inheritance. This tendency of genes in a chromosome to remain together is called ‘Linkage’. This linkage is not absolute and the genes do not remain locked up in the same chromosome for ever. Otherwise the inheritance of traits would also have remained constant. During meiosis the homologous chromosomes come together and form pairs, a process called ‘Synapsis’. Soon after they sometimes exchange segments mutually, a process is called ‘Crossing over’. This exchange occurs ranelonly along the length of chromosome. After separation the chromosomes carry some genes that were earlier located in different member of their pair of homologous chromosome. Such exchanges of chromosomal segments or crossing over may occur at more than one point in homologous chromosomes in single meiotic division.

Genetic Engineering (Short Note)

It is the manipulation of genetic material of any organism. Genetic engineering usually utilize bacterial cells and their plasmids, which are small circular DNA molecule. They can replicate feely within bacterial cells. Genetic engineering can produce cells that contain a foreign gene. These results ar capable of producing new and different Protein. As a result of growth of these cells so many identical copies of plasmid with a foreign gene are produced.

Genetic engineering bacteria can be used in the environment, for serving in the field of agriculture etc. These bacteria can also be used to promote health of plants to make them resistant towards insects as bioremediation (pollution cleaner) to synthesize organic chemicals to dect metals, to enhance genetic research to produce pharmaceutical products. In agriculture these bacteria can be used to promote the health of plant in different ways.

Genotype (Short Note)

The sum total of all the hereditary units or genes which an organism contains are together known as genotypes. Briefly it means that phenotypes are not inherited, only the genes which control the development of phenotypes are indeed inherited. Whatever is the phenotype of an animal, it is not the result of genotype only but is accumulative result of the interaction of the genotype and environment. The organism having same genotype might produce different phenotypes in different types of environment. However the ability of an organism to produce a character is largely determined by its genotype, although the environment can modify the action of a gene. In brief neither the genes alone nor environment alone can produce a character. The development of phenotype actually depends upon the factors i.e. genes and surrounding environment.

Phenotype (Short Note)

All the physical appearances by which recognize an individual are together known as phenotypes. For example rabbit has specific shape and structure which includes so many characteristics i.e. length of legs, length of ears, length of tail, mouth, abdomen, thorax etc: and overall body shape. Almost of all the animals, plants, bacteria and viruses are bio-chemically very similar. Therefore we can say that the phenotype may be visual, microscopic, structural, fundamental or biochemical i.e. phenotype of metabolism of the process of photosynthesis, the transmission of nerve impulse along the nerve fibres, muscular contraction, blood circulation the development of secondary sexual characters and the photoperiodism and the fall of leaves in some trees are examples of physiological phenotypes. Phenotype may be of reproductive capacity. Reproduction may be at molecular level, cellular level (gametes) or individual level. Phenotype is combination of many features which together contribute to the characteristic phenotype of an individual.

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