Guide To Learn
Griffith Transformation In 1928, Frederick Griffith performed the first experiment to prove that DNA was the hereditary material. Griffith selected the bacterium that causes pneumonia, Diplococcus pneumoniae. Two strains of the bacterium namely virulent strain and avirulent strain were used for the study. Virulence required the presence of a polysaccharide capsule around the bacterium. The avirulent […]
The Chromosomal DNA The DNA molecule may be circular or linear and can be composed of 100,000–10,000,000,000 nucleotides in a long chain. Typically, eukaryotic cells (cells with nuclei) have large linear chromosomes and prokaryotic cells (cells without defined nuclei) have smaller circular chromosomes, although there are many exceptions to this rule. In addition, cells may […]
There are four types of RNA, each encoded by its own type of gene: Figure 1.9 Structure of a eukayotic mRNA Messenger RNA ‘The genetic information stored in the DNA, inside the nucleus, is conveyed to the ribosomes in the cytosol for the synthesis of proteins through the mRNA. Thus, the mRNA carries the genetic […]
The double-stranded structure of a DNA determines its biological function. Metabolic events involving unwinding impose great stress on the DNA because of the constraints inherent in the double helix. Molecular processes such as replication and transcription require the unwinding of the DNA double helix. While unwinding, correct topological tension in the DNA (super-helical density) should […]
Physical Properties of the DNA Size and shape The DNA molecules range in length from about 2 microns (virus) to 2.1cm (Drosophila’s largest chromosome) to 1.6—8.2 cm (human chromosome) (1 kb DNA = 103 base pairs = 0.34 × 10-6 m). Some DNA molecules are circular (E. coli chromosome, mitochondrial DNA, plasmidDNA) and some are linear (human DNA, T7 […]
The Chemical Nature of DNA and RNA The backbone of a nucleic acid is made of alternating pentose ‘sugar’ (deoxyribose sugar in DNA and ribose sugar in RNA) and ‘phosphate’ molecules bonded together in a long chain. Each of the sugar groups in the backbone is attached to ‘nitrogenous base’. The ‘2′-deoxy-’ notation means that […]
DNA In most living organisms (except viruses), the genetic information is stored in the molecule called deoxyribonucleic acid or DNA. DNA is made and it resides in the nucleus of the living cells. The name DNA was derived from the sugar molecule contained in its backbone—deoxyribose. The high molecular weight nucleic acid, DNA, is found […]
The complex systems of living organisms encompass hundreds to thousands of proteins that exist help us to carry out our daily functions. The information required to manage this complex system is stored in a set of molecules called ‘nucleic acids’. The three most abundant biological macromolecules are ‘proteins’, ‘nucleic acids’ and ‘polysaccharides’. The information-carrying molecules […]