DNA PDF

BY AMRITA MA’AM DNA ▪ Nucleic acid A phosphate group is just a phosphorus atom ▪ Nucleic acids are the biopolymers, or bound to four oxygen atoms, but it has many small biomolecules, essent...

BY AMRITA MA’AM DNA ▪ Nucleic acid A phosphate group is just a phosphorus atom ▪ Nucleic acids are the biopolymers, or bound to four oxygen atoms, but it has many small biomolecules, essential to all important roles. known forms of life. ▪ The nucleic acid is of two types: ▪ DNA ( deoxyribonucleic acid ) ▪ RNA (ribonucleic acid ). ▪ They are composed of three components: ▪ 5-carbon sugar (pentose sugar) History ▪ phosphate group Nuclein were discovered by Friedrich Miescher ▪ nitrogenous base. in 1869. Father of nucleic acid – Friedrich Miescher. The sugars found in nucleic acids are pentose In 1889 Richard Altmann creates the term sugars; a pentose sugar has five carbon nucleic acid. atoms. DNA DNA, or deoxyribonucleic acid, is the hereditary material in humans and almost all other organisms. Nearly every cell in a person’s body has the same DNA. Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria and chloroplast. DNA was discovered in 1869 by Swiss researcher Friedrich Miescher on white blood cells. He isolated a new molecule he called nuclein Nucleoside from a cell nucleus. A nucleoside is formed by the addition of a In 1953 James Watson and Francis Crick, nitrogenous base and a sugar. aided by the work of biophysicists Rosalind The base and the sugar are linked together by Franklin and Maurice Wilkins, determined an N-glycosidic linkage bond. that the structure of DNA is a double- nucleotide helix polymer, a spiral consisting of two DNA A nucleotide is formed when a phosphate strands wound around each other. group is attached to a nucleoside by a “phosphoester linkage” bond. Watson-Crick Model of DNA: polynucleotide In 1953, J.D. Watson (an American biologist) When two nucleotides are joined together by and F.H.C. Crick (a British Physicist) proposed a phosphodiester bond, a polynucleotide is the three-dimensional model of physiological formed. DNA (i. e B-DNA) on the basis of X-ray diffraction data of DNA obtained by Franklin and Wilkins. For this epoch-making discovery, Watson, Crick and Wilkins got Nobel Prize in medicine in 1962. Term DNA was given by Zaccharis. DNA is polynucleotide डीएनए पॉलीन्यूक्लियोटाइड है DNA Is a Polynucleotide. The Important Features 1. The DNA molecule consists of two polynucleotide chains or strands that spirally twisted around each other and coiled around a common axis to form a right-handed double- helix. 2. The two strands are antiparallel i.e. they ran in opposite directions so that the 3′ end of one chain facing the 5′ end of the other. Extra Points DNA is the carrier of genetics. The part of DNA that provides information for proteins is called “Gene”. 6.The base sequence along a polynucleotide chain is variable and a specific sequence of Gene is unit of genetics. bases carries the genetic information. Anotation : The process of marking genes in a 7. The base compositions of DNA obey DNA sequence. Chargaff s rules. 8. The diameter of DNA is 2.0nm or 20 A. Adjacent bases are separated 0.34 nm or by 3.4 A along the axis. The length of a complete turn of helix is 3.4 nm or 34 A i.e. there are 10bp per turn. (B- DNA-Watson rick DNA) 9. The DNA helix has a shallow groove called minor groove (-1,2nm) and a deep groove called major groove (- 2.2nm) across. Chargraff’s Rule Discovered by Erwin Chargaff (in 1950). It specifies that the amounts of guanine and cytosine be the same. While the ratios of adenine and thiamine are the same. Three major forms of DNA A-form DNA B-form DNA Z-form DNA