DNA(Deoxyribonucleic Acid) | Structure | History | X-Ray Crystallography.....

 DNA(Deoxyribonucleic Acid)

DNA (Deoxyribonucleic acid)

It is a molecule composed of two polynucleotide chains that coil around each other to form a double helix, carrying genetic instructions for the development, functioning, growth and reproduction of all organisms and many viruses. 

                                            or

DNA is a self replicating material which is present in nearly all living organisms as the main constituents of chromosomes. It is the carrier of genetic information.

                                            or

It is the hereditary material in humans and almost all other organisms. Nearly every cell in a person's body has the same DNA.

The two DNA strand are know as polynucleotides as they are composed of simpler monomeric units called nucleotide. Each nucleotide is composed of one of four nitrogen containing nucleobases (cytosine C, guanine G, adenine A, thymine T) a sugar called the deoxyribose, and a phosphate group. The nucleotides are joined to one another in a chain by covalent bonds(also know as phospho-diester linkage). A strand binds to T with double bond  (A=T) and G strand binds to C with triple bond (G=C). Both strands of double-stranded DNA store the same biological information. The two strands of DNA run in opposite directions to each other and are thus antiparallel (3' to 5' direction and 5' to 3' direction). RNA  strands are created using DNA strands as a template in a process called transcription, where DNA bases are exchanged for their corresponding bases except in the case of thymine (T), for which RNA substitutes uracil (U). Under the genetic code, these RNA strands specify the sequence of amino acid within proteins in a process called translation.

HISTORY :-

1) Johannes Friedrich Miescher

                                                             Johannes Friedrich Miescher

DNA was first isolated by Friedrich Miescher in 1869. Miescher isolated various phosphate-rich chemicals, which he called nuclein (now nucleic acids), from the nuclei of white blood cells in 1869 in Felix Hoppe-Seyler's laboratory at the University of Tubingen, Germany, paving the way for the identification of DNA as the carrier of inheritance. He was the first scientist to isolate nucleic acid. 

2) Rosalind Elsie Franklin :-

                                                            Rosalind Elsie Franklin

Rosalind Elsie Franklin (25 July 1920 – 16 April 1958) was an English chemist and X-ray crystallographer  whose work was central to the understanding of the molecular structures of DNA (deoxyribonucleic acid), RNA (ribonucleic acid), viruses, coal, and graphite.

X-Ray Crystallography

X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-ray to diffract into many specific directions. By measuring the angles and intensities of these diffracted beams, a crystallographer can produce a three-dimensional picture of the density of electrons within the crystal. From this electron density the mean positions of the atoms in the crystal can be determined, as well as their chemical bonds, their crystallographic disorders, and various other information. The method also revealed the structure and function of many biological molecules, including vitamins, drugs, proteins, and nucleic acids such as DNA. X-ray crystallography is still the primary method for characterizing the atomic structure of new materials and in discerning materials that appear similar by other experiments. X-ray crystal structures can also account for unusual electronic or elastic properties of a material, shed light on chemical interactions and processes, or serve as the basis for designing pharmaceuticals against diseases.

3)  Francis Crick and James Watson

    

                                              Francis Crick and James Watson

Late in 1951, Francis Crick started working with James Watson at the Cavendish laboratory within the University of Cambridge In February 1953, Linus Pauling and Robert Corey proposed a model for nucleic acids containing three intertwined chains, with the phosphates near the axis, and the bases on the outside.

PROPERTIES :-

• Nucleobase Classification 
• Non-canonical bases 
• Listing of non-canonical bases found in DNA
• Grooves
• Base pairing
• Sense and Antisense
• Supercoiling
• Alternative DNA structure
• Alternative DNA chemistry
• Quadruplex structures
• Branched DNA
• Artificial bases

USES IN TECHNOLOGY

1) DNA Profiling :- Forensic scientists can use DNA in blood, semen, skin, saliva, or hair found at a crime scene to identify a matching DNA of an individual, such as perpetrator. This process is formally termed DNA profiling also called as DNA fingerprinting.

2) DNA Enzymes or catalytic DNA :- Deoxyribozymes also called DNAzymes or catalytic DNA, were first discovered in 1994. DNAzymes catalyze variety of chemical reactions including RNA-DNA cleavage, RNA-DNA ligation, amino acids phosphorylation- dephosphorylation, carbon-carbon bond formation, etc. DNAzymes can enhance catalytic rate of chemical reactions up to 100,000,000,000-fold over the uncatalyzed reaction.

3) Bioinformatics :- It involves the development of techniques to store, data-mine, search and manipulate biological data, including DNA nucleic acid sequence data.

4) Genetic Engineering :- The methods have been developed to purify DNA form organisms, such as phenol-chloroform extraction, and to manipulate it in the laboratory, such as restriction digest and the polymerase chain reaction.

5) DNA Nanotechnology :- It uses the unique molecular recognition properties of DNA and other nuclein acids to create self-assembling branched DNA complexes with useful property.

6) CRISPR Technology :- CRISPR is a family of DNA sequences found in the genomes of prokaryotic organisms such as bacteria and archaea. This sequences are derived from DNA fragments of bacteriophages that had previously infected prokaryotes.

7) NGS (Next Generation Sequencing) :- Massive parallel sequencing is any of several high-throughput approaches to DNA sequencing using the concept of massively parallel processing; it is also called next generation sequencing.

Subscribe for more information.........