The Molecular Basis Of Inheritance

The lac operon consists of one regulatory gene (the -gene) and three structural genes ( and ). The -gene codes for the represser of the lac operon. The -gene codes for -galactosidase ( -gal), which is primarily responsible for the hydrolysis of the disaccharide, lactose into its monomeric units, galactose and glucose. The -gene codes for permease, which increases permeability of the cell to -galactosides. The -gene encodes a transacetylase.

The negatively charged DNA is wrapped around the positively charged histone octomer to form a structure called nucleosome. A typical nucleosome contains of DNA helix.

RNA polymerase II occur in nucleoplasm (a part of nucleus). It is a major component of RNA polymerase activity and transcribe mRNA producing gene. In eukaryotic organisms it transcribes hnRNA (an intial form of mRNA precursor) which are late on processed into mRNA, while m-RNA are transcribed by RNA polymerase-I.

The heterogeneous nuclear is the precursuor of mRNA, It undergoes splicing, capping and tailing during the process. In E splicing, the introns are removed and exons are joined in a defined order undergoes someone processing called as capping and tailing. In capping an unusual nucleotide (methyl guanosine triphosphate) is added to the -end of . In tailing, adenylate residues are added at -end in a template independent manner. It is the fully processed , now called mRNA. It is transported out of the nucleous for translation.

Francis Crick first postulated the presence of an adapter molecule that would on one hand read the code and on other hand would bind to specific amino acids. The then called (soluble RNA), was known before the genetic code was postulated. However, its role as an adapter molecule was assigned much later. has an anticodon loop that has three bases complementary to the code and also has an amino acid accepter end to which it binds to amino acids.

Edward Southern in first developed the technique Southern blotting. It is used in DNA fingerprinting. The probes or markers that are radioactive synthetic DNA segments target a specific nucleotide sequence which is complementary to VNTRs sequences and hybridises them.

When nucleotides are incorporated into DNA, adjacent nucleotides are linked by a phosphodiester bond formed between phosphate group of carbon of one nucleotide and of carbon of another nucleotide.