Packaging of DNA Helix
· Distance between two conjugative base pairs is 0.34nm, the length of the DNA in a typical mammalian cell will be 6.6 X109 bp X 0.34 X10-9 /bp, it comes about 2.2 meters.
· The length of DNA is more than the dimension of a typical nucleus (10-6m), how is such a long polymer packaged in a cell.
Packaging in prokaryotes:
· They do not have definite nucleus.
· The DNA is not scattered throughout the cell.
· DNA is held together with some proteins in a region is called ‘nucleoid’.
· The DNA in nucleoid is organized in large loops held be proteins.
Packaging in Eukaryotes:
DNA fingerprinting is the technique where DNA sequences of two individuals are compared. It is widely used in the identification of paternity.
Genetic code is a triplet sequences of bases that codes for particular amino acids that further helps in protein synthesis. Mutations are sudden change; it can be point mutation or frame shift mutation.
Ribonucleic acid and deoxyribonucleic acid are nucleic acids which are differ from each other in the presence of thymine in DNA and uracil in RNA.
Transcription is a process where DNA is converted into RNA by the help of RNA polymerase. Information of DNA is copied into mRNA for the synthesis of protein. After RNA synthesis it is modified further by the process of post transcriptional modification.
Translation is a process of synthesis or formation of protein from mRNA. Three process like initiation, elongation and termination are involve in translational process.
Replication is a process of copying of DNA. Messelson and stahl done an experiment to prove that DNA is of semi-conservative in nature where one strand is antisense or template strand and other strand is sense or leading strand.
Genetic material was searched by the help of following experiments. Frederick Griffith done an experiment on streptococcus pneumoniae to recovered genetic material. Avery, Mccarty and Macleod identify the biochemical nature of genetic material.
Expression of genes can be regulated by lac operon model which was proposed by Jacob and Monad. The regulation of lac operon by repressor is known as negative regulation.