Explain the process of protein synthesis from processed m-RNA.

OR

Which methodology is used while sequencing the total DNA from a cell? Explain it in detail.

Translation is the process of forming amino acids to from a polypeptide chain from a fully mature mRNA. The sequence of bases in the mRNA determines the sequence of amino acids. The amino acids are linked by peptide bonds. Initially, the amino acids bind to the amino acid acceptor ends of their respective tRNA in the presence of ATP. This process is called charging of tRNA or aminoacylation of tRNA. When the charged tRNA are brought close to each other, peptide bonds are formed between the amino acids. This whole process of protein synthesis occurs in the ribosomes. The ribosome has two subunit – larger subunit and smaller subunit. It is the smaller subunit which carries the mature mRNA and initiates translation. The ribosomes play a dual role :they act as centres of protein synthesis as well as act as catalysts for the formation of peptide bonds. The smaller subunit of ribosomes move from one codon to another on the mRNA and accordingly amino acids are added. Translation is terminated by the binding of release factor to the stop codon.

OR

The methodology used while sequencing the total DNA from a cell was called HGP or Human Genome Project. It was a mega project. It took 13 years to complete the sequencing of the entire human genome. This project was coordinated by the US Department of Energy and the National Institute of Health. It was a costly project and contributions came from Japan, France, Germany, China. The entire project was completed in 2003. This mega project provided a clear understanding of human biology. By studying the genome of an organism, a lot of future benefits can be gained. The challenges which we face in areas of health care, agriculture, energy production, environmental remediation, can all be overcome by genome projects.

The methodologies had various approaches towards identifying genes. One approach focused on identifying the genes which were expressed as RNA. Then sequencing takes place by taking and isolating the entire DNA of a cell and processing them into smaller fragments. They are then ligated to vectors and cloned in a suitable host. Cloning is nothing but the amplification of each DNA fragment. Frederick Sanger developed a method of sequencing the DNA fragments in automated DNA sequencers. All the steps can’t be fulfilled by humans. Therefore computer programs which were specially developed for this purpose were used which helped in studying the overlapping regions of DNA fragments. Hence gradually the entire genome was cracked.