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Nucleic acid..biochem

  1. 1. Presented by : Dr Nainika Sharma Periodontology first year PG
  2. 2.  Frederic Miesher in 1869, isolated an acidic compound from the nuclear material of SALMON sperms, and named it as NUCLEIN which is now called NUCLEIC ACID.  Jones in 1920 proved the fact there are two types of nucleic acids, i.e., Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA).  In 1935 J. D. Watson and F. H. C Crick, on the basis of information available not only proposed the “Double helical” structure of DNA but also suggested what Crick termed “central dogma of molecular genetics”, which states that genetic information flows from DNA to RNA to protein.
  3. 3. DNA  RNA  amino acids  proteins
  4. 4.  Was trying to develop a vaccination for the pneumococcus bacteria.  Vaccine- a prepared substance from killed or weakened disease causing agents used to prevent future infections  He was working with two strains of bacteria.  Rough - bacteria had a rough appearance in culture, non-virulent (doesn't kill)  Smooth - bacteria had a smooth appearance in culture, virulent (kills)
  5. 5. The Genetic Material is DNA – Alfred Hershey and Martha Chase, 1952 Previously, scientists thought that proteins were the hereditary molecule Hershey and Chase worked with viruses that infect bacteria called bacteriophages › Through a series of experiments, they were able to show that DNA, not protein, is the hereditary molecule.
  6. 6. M.H.F. Wilkins and Rosalind Franklin, early 50’s Wilkins and Franklin studied the structure of DNA crystals using X-rays. They found that the crystals contain regularly repeating subunits. The X pattern produced by DNA suggested that DNA contains structures with dimensions of 2 nm, 0.34 nm, and 3.4 nm. The dark structures at the top and bottom indicate that some structure was repeated, suggesting a helix.
  7. 7. Rosalind Franklin X-ray diffraction image of DNA
  8. 8. James Watson and Francis H.C. Crick, 1953 Watson and Crick used Chargaff's base data and Franklin’s X-ray diffraction data to construct a model of DNA. The model showed that DNA is a double helix with sugar-phosphate backbones on the outside and the paired nucleotide bases on the inside, in a structure that fit the spacing estimates from the X-ray diffraction data. Chargaff's rules showed that A = T and G = C, so there was complementary base pairing of a purine with a pyrimidine, giving the correct width for the helix. The paired bases can occur in any order, giving an overwhelming diversity of sequences.
  9. 9. Watson & Crick with their model of DNA
  10. 10.  Base pairing rule is A-T and G-C.  Thymine is replaced by Uracil in RNA.  Bases are bonded to each other by Hydrogen bonds.  Discovered because of the relative percent of each base; (notice that A-T is similar and C-G are similar).
  11. 11. Erwin Chargaff
  12. 12.  The role of RNA in protein synthesis was suspected already in 1939.  Severo Ochoa won the 1959 Nobel Prize in Medicine after he discovered how RNA is synthesized.  Carl Woese realized RNA can be catalytic in 1967 and proposed that the earliest forms of life relied on RNA both to carry genetic information and to catalyze biochemical reactions—an RNA world.
  13. 13.  In 1990 it was found that introduced genes can silence homologous endogenous genes in plants, now known to be a result of RNA interference.  In same year, the discovery of gene regulatory RNAs has led to attempts to develop drugs made of RNA, like siRNA, to silence genes.
  14. 14.  Two types;  DNA  RNA  The building blocks of nucleic acids are called NUCLEOTIDES
  15. 15.  Nucleotides: monomers of nucleic acids. › All nucleic acids consist of many nucleotides bonded together.  Nucleic acids are polynucleotide.  Their building blocks are nucleotides
  16. 16.  nucleotides, are made up of three parts: (a) Phosphate (phosphoric acid) (b) N-base (Nitrogenous base) (c) Sugar ~ ribose or deoxyribose
  17. 17. PHOSPHATE SUGAR Ribose or Deoxyribose NUCLEOTIDE BASE PURINES PYRIMIDINES Adenine (A) Guanine(G) Cytocine (C) Thymine (T) Uracil (U)
  19. 19.  Purines: adenine, guanine (double ring)  Pyrimidine: thymine, cytosine (single rings) Adenine : Thymine : Guanine : Cytosine :
  20. 20. The bases always pair up in the same way A purine with a pyrimidine Adenine forms a bond with Thymine Cytosine bonds with Guanine Adenine Thymine Cytosine Guanine
  21. 21.  Sugar = Deoxyribose  Specific Base Pairing › Adenine-Thymine › Guanine-Cytosine  Forms a double Helix Structure
  22. 22.  Sugar= Ribose  Thymine gets replaced by Uracil  Single stranded
  23. 23. Molecule: DNA RNA Structure /shape Double helix or α-helix Linear, single strand # of strands 2 1 Sugar Deoxyribose Ribose N-bases A, T, G, C A, U, G, C Structural (and functional) Comparison of DNA & RNA
  24. 24.  DNA is used to store genetic information › It is replicated before cell division.  DNA is very important so it is stored in the nucleus.  It never leaves the nucleus  Your DNA stores the code for your proteins, which exhibit your “traits”  The DNA gets converted to RNA in order to move out into the cytoplasm
  25. 25.  In the cytoplasm it meets up with the ribosome, where it can synthesize proteins  Stores genetic information.  Maintains growth and repair.  Controls all cellular activities.  Contains protein codes.  Ensures each daughter cell & gamete receives exact genetic information.
  26. 26.  Abbreviation of deoxyribonucleic acid.  It is a polymer of Deoxyribo nucleotide.  This thread like structure is a combination of large number of nucleotide units joined together.  This Polynucleotide contains genetic information that gives rise to chemical and physical properties of organisms.
  27. 27.  LOCATION:  It can be found in chromosomes (specifically nucleus), mitochondria and chloroplast of the cell.  It is present in every living organism because it contains genetic material.  ISOLATION:  From viruses, bacteria, thymus gland, spleen, blood, hair, skin, etc
  28. 28.  Size shows great variation.  Only 1.7µm long in simple structure of simian virus with 5 or 6 genes. and can also extend to 2m in Human DNA.  The size of human DNA inside the chromosome is just 200 nm.
  29. 29.  In fact, the DNA usually consists of a double strand of nucleotides.  The sugar-phosphate chains are on the outside and the strands are held together by hydrogen bonds between the bases.  There are grooves in the DNA molecule: minor groove and major groove, winding along the molecule parallel to the phosphodiester backbone.
  30. 30. The bases always pair up in the same way A purine with a pyrimidine Adenine forms a bond with Thymine and Cytosine bonds with Guanine Adenine Thymine Cytosine Guanine
  31. 31. PO4 PO4 PO4 thymine PO4 PO4 PO4 PO4 adenine cytosine PO4 guanine
  32. 32.  Two types;  Circular DNA  Non-Circular DNA  CIRCULAR DNA :  In Eukaryotes: The ends of DNA are cohesive,so they join forming a circular,chloroplast,etc.  In Prokaryotes: mostly it is in the form of PLASMID whose replication do not depend on genomic
  33. 33.  NON-CIRCULAR DNA:  The two anti parallel strands of DNA twist around each other to form helical structure of double helix.
  34. 34. 1) DNA must unwind and break the hydrogen bonds 2) Each strand is used as a template (blueprint) 3) Two new strands of DNA are formed from the original strand by the enzyme DNA Polymerase
  35. 35. During replication, an enzyme called helicase “unzips” the DNA molecule along the base pairing, straight down the middle. Another enzyme, called DNA polymerase, moves along the bases on each of the unzipped halves and connects complementary nucleotides.
  36. 36. DNA polymerase Replication fork Growth Growth New strand Original strand DNA polymerase New strand Original strand Replication fork Nitrogenous bases
  37. 37.  Just as DNA polymerase makes new DNA, a similar enzyme called RNA polymerase makes new RNA.  RNA polymerase temporarily separates the strands of a small section of the DNA molecule. › This exposes some of the bases of the DNA molecule.  Along one strand, the RNA polymerase binds complementary RNA nucleotides to the exposed DNA bases.
  38. 38.  As the RNA polymerase moves along, it makes a strand of messenger RNA (mRNA). › It is called messenger RNA because it carries DNA’s message out of the nucleus and into the cytoplasm. › mRNA is SINGLE STRANDED!  When the RNA polymerase is done reading the gene in the DNA, it leaves.  The separated DNA strands reconnect, ready to be read again when necessary.  mRNA moves out of the nucleus and finds a ribosome  On the ribosome, amino acids are assembled to form proteins in the process called translation.
  39. 39. A C G G T A TEMPLATE STRAND T TG C C A The backbone is made of alternating sugars and phosphates. - Remember: Sugar ALWAYS attaches to the Nitrogen base
  40. 40.  Ribonucleic acid usually called as RNA, is a biologically important type of molecule that consists of a long chain of nucleotide units.  It is a single stranded chain of nucleotides that contains genetic information and it functions for the synthesis of proteins and also to transfer genetic information from one generation to the next.
  41. 41.  There are three types of RNA in a cell.  Ribosomal RNA (rRNA)  Messenger RNA (mRNA)  Transfer RNA ( tRNA) • Their main function is to make proteins after taking instructions from the DNA. • They are temporarily present in the cell.
  42. 42. from to to make up also called which functions to also called also calledwhich functions to can be RNA Messenger RNA Ribosomal RNA Transfer RNA mRNA Carry instructions rRNA Combine with proteins tRNA Bring amino acids to ribosome DNA Ribosome Ribosomes Which functions to
  43. 43.  Also known as mRNA.  Messenger RNA is a single long chain of nucleotides  It is a molecule of RNA encoding a chemical "blueprint" for a protein product.  mRNA istranscribed from a DNA template, and carries coding information to the sites of protein synthesis: the ribosomes.
  44. 44.  In mRNA as in DNA, genetic information is encoded in the sequence of nucleotides arranged into codons consisting of three bases each.  Each codon encodes for a specific amino acid, except the stop codons that terminate protein synthesis.
  45. 45.  It is also known as rRna.  Ribosomal RNA is the central component of the ribosome, the protein manufacturing machinery of all living cells.
  46. 46.  Ribosomal RNA has two units,  one large and  the other small. . Large subunit Small subunit Ribosomal RNA (rRNA)
  47. 47.  The function of the rRNA is to provide a mechanism for decoding mRNA into amino acids and to interact with the tRNAs during translation.  The tRNA then brings the necessary amino acids corresponding to the appropriate mRNA codon.
  48. 48.  Transfer RNA (abbreviated tRNA) is a small RNA molecule (usually about 74-95 nucleotides) that transfers a specific active amino acid to a growing polypeptide chain at the ribosomal site of protein synthesis during translation.  act as adapter between nucleotides codons and amino acids. They pick up free amino acids in cytoplasm and carry them into the ribosomes where polypeptide chain is elongated.
  49. 49.  Each tRNA carries an amino acid  As each codon of the mRNA molecule moves through the ribosome, the corresponding amino acid is brought into the ribosome by the tRNA.  Each tRNA molecule has three unpaired bases (anticodons)which are complimentary to mRNA codons
  50. 50.  There are 20 different tRNAs, for the different aminoacids.
  51. 51.  tRNA carries (or transfers) the correct amino acid to the codon on the mRNA.  tRNA has an ANTICODON that can attach to mRNA’s codon.
  52. 52.  mRNA is sandwiched between the small and large subunits and the ribosome catalyzes the formation of a peptide bond between the 2 amino acids that are contained in the rRNA.  The ribosome also has 3 binding sites called A, P, and E.  The A site in the ribosome binds to an aminoacyl-tRNA (a tRNA bound to an amino acid).
  53. 53.  The amino (NH2) group of the aminoacyl-tRNA, which contains the new amino acid, attacks the ester linkage of peptidyl-tRNA (contained within the P site), which contains the last amino acid of the growing chain, forming a new peptide bond.  The tRNA that was holding on the last amino acid is moved to the E site, and what used to be the aminoacyl-tRNA is now the peptidyl-tRNA.  A single mRNA can be translated simultaneously by multiple ribosomes.
  54. 54. Translation- the Ultimate Goal! •Going from mRNA to the final product
  55. 55.  How does DNA (a twisted latter of atoms) control everything in a cell and ultimately an organism? › DNA controls the manufacture of all cellular proteins including enzymes › A gene is a region of DNA that contains the instructions for the manufacture of on particular polypeptide chain (chain of amino acids) DNA is a set of blueprints or code from making proteins
  56. 56. Where is the DNA? Protein synthesis – the manufacture of proteins Where are proteins made in the cell?
  57. 57.  mRNA combines with a ribosome and tRNA and makes a protein  Remember: › mRNA carries the codon (three base sequence that codes for an amino acid) › tRNA carries the anticodon which pairs up with the codon › tRNA brings the correct amino acid by reading the genetic code
  58. 58. GUA UCU GUU ACC GUA mRNA •mRNA carries the same message as DNA but rewritten with different nitrogen bases. •This message codes for a specific sequence of amino acids •Review..Amino acids are the building blocks of… •PROTEINS
  59. 59. GUA UCU GUU ACC GUA mRNA •Codon: a sequence of 3 nitrogen bases on mRNA that code for 1 amino acid •It’s a TRIPLET code
  60. 60. GUA UCU GUU ACC GUA mRNA •These codons are universal for every bacteria, plant and animal on earth •There are 64 codons which code for all 20 amino acids on earth.
  61. 61. GUA UCU GUU ACC GUA mRNA •The mRNA molecule travels to the ribosomes where the mRNA codes are “read” by the ribosomes •Ribosomes hold the mRNA so another type of RNA, transfer RNA (tRNA) can attach to the mRNA Ribosome
  62. 62. GUA UCU GUU ACC GUA mRNA RibosomeCAU AGA
  63. 63.  Amino acids link together to form a protein  The new protein could become cell part, an enzyme, a hormone etc.
  64. 64.  Say the mRNA strand reads: › mRNA (codon) AUG–GAC–CAG-UGA › tRNA (anticodon) UAC-CUG-GUC-ACU  tRNA would bring the amino acids:  Methionine-Aspartic acid-Glutamine-stop
  65. 65. 1)mRNA is transcribed in the nucleus and leaves the nucleus to the cytoplasm. 2) mRNA attaches to the ribosome. 3)The codon on the mRNA is read by the anticodon on the tRNA. 4) tRNA brings the amino acid as it reads mRNA. 5) The amino acids are joined together to form a polypeptide (protein). 6) When a stop codon is reached (UAA, UAG, UGA) protein synthesis stops.
  66. 66.  A probe is a molecule with a strong affinity for a specific target, which can be easily detected after its interaction with the target.  Specificity depends based on the interaction between complementary polynncleotide strand.  Probes obtained by amplification of naturally occurring DNA sequence or chemical synthesis.
  67. 67.  DNA based technique is used in  Genetic diseases  Cancers  Slow growing / difficult isolation bacterial infections
  68. 68.  Telomerase activity maintain appropriate length of the telomer sequences of chromosome.  This activity is absent in most somatic cells leads to decrease in the telomer repeating and substantial reduction of the telomer.  Telomer length appears to serve as a mitotic clock that limit the replication potential of mammalian cells.
  69. 69.  Genetic material is rearranged by breaking and joining portion of the same DNA molecule or portion of different DNA molecule.  Recombination takes place between DNA of different organism to generate new composite DNA.
  70. 70.  DNA Recombination technology used for  Antibodies  Proteins  Production of more disease resistance in organisms
  71. 71.  DNA can be collected from hair, tooth, blood, saliva, sweat, semen, urine, bone, tissues and cellular contents.  After extracting DNA from various method and used for  Gender identification  Personal identification  Parental disputes, etc.
  72. 72.  Nucleic acids are the multicoded complex molecule in the biological system from virus to humans.  Exploring the nature, properties, possible to understand the molecules and to bring the desirable modification in the future world for the benefits of living system.
  73. 73.  Text Book Of Medical Biochemistry, MN Chatterjea, Rana Shinde, 3rd Edition.  Text Book Of Biochemistry, U. Satyanarayana, 2nd Edition.  Text Book Of Biochemistry With Clinical Correlations, Thomas M. Devlin, 4th Edition.  Role of DNA in forensic odontolgy, Shruthi Nayak, KSDJ vol- 31:no-01;jan-march 2012.  Harper 29 th edition …pg.336 to 352