NUCLEIC ACIDS DNA, RNA & Protein Synthesis SDK September 24, 2013

1. NUCLEIC ACIDSDNA, RNA &Protein SynthesisSDKSeptember 24, 2013

2. Road Map • What is nucleic Acid • Types of nucleic acid • Structural and functional characeristics of nucleic acid • Nomenclature of Nucleic Acid Components • DNA • Definition • Structure of DNA • Types of DNA • DNA & Chromosomes • RNA • Definition • Structure& function of RNA • Difference between DNA & RNA • Protein and Gene Expression • Protein Synthesis • Transcription • DNA Intones and Exons • Translation • Polypeptide chain • Termination codon • Summary • Brain Work

3. Nucleic Acids • Are the organic molecules derived from the nucleus. Friedrich Miescher in 1869 • Isolated what he called nucleinfrom the nuclei of pus cells • Nuclein was shown to have acidic properties, hence it became called nucleic acid

4. Types of Nucleic Acid • Deoxyribonucleic acid (DNA) • Ribonucleic acid (RNA)

5. The Distribution of Nucleic Acids in The Human Cell • DNA is found in the nucleus with small amounts in mitochondria • RNA is found throughout the cell

6. Nucleic Acid Structure • Nucleic acids are polynucleotides • Their building blocks are nucleotides

7. Nucleic Acid Structure • Primary- Basic component of NA • Secondary- Nucleoside and nucleotides • Tertiary- Formation of poly nucleotide chain • Quaternary- Pairing of two poly nucleotide chains

10. Basic structure of Purine & Pyrimidine

11. Pyrimidines

12. Purines

17. Nucleic Acid Structure 3 5

18. Nomenclature of Nucleic Acid Components Base Nucleoside Nucleotide Nucleic acid Purines Adenine Adenosine Adenylate RNA Deoxyadenosine Deoxyadenylate DNA ------------------------------------------------------------------------------------- Guanine Guanosine Guanylate RNA Deoxy guanosine Deoxyguanylate DNA ------------------------------------------------------------------------------------- Pyrimidines Cytosine Cytidine Cytidylate RNA Deoxycytidine Deoxycytidylate DNA ------------------------------------------------------------------------------------- Thymine Thymidine Thymidylate DNA -------------------------------------------------------------------------------------Uracil Uridine Uridylate RNA

19. Nucleoside and base analogs can be used as anti-cancer and anti-virus drugs Anticancer agents 5-Fluorouracil 6-Mercaptopurine Antiretroviral agents Azidothymidine Dideoxyinosine

24. DNA

25. Double Helix of 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 (where it is called mitochondrial DNA or mtDNA). • Human DNA consists of about 3 billion bases, and more than 99 percent of those bases are the same in all people. Why the people are different from each other The order, or sequence, of these bases determines the information available for building and maintaining an organism, similar to the way in which letters of the alphabet appear in a certain order to form words and sentences. • DNA contains two strands of nucleotides • H bonds hold the two strands in a double-helix structure • A helix structure is like a spiral stair case • Bases are always paired as A–T and G-C • Thus the bases along one strand complement the bases along the other

26. The primary structure of DNA is the sequence • Traditionally, a DNA sequence is drawn from 5’ to 3’ end. • A shorthand notation for this sequence is ACGTA

27. The 2ndry structure of DNA is a Double Helix of DNA

29. DNA Types

30. Normally DNA is B-form DNA • Helix : right handed • Base pairs: almost perpendicular to the helix axis; 3.4 Å apart • One turn of the helix: 36 Å; ~10.4 base pairs • Minor groove: 12 Å across • Major groove: 22 Å across

31. In eukaryotic cells, DNA is folded into chromatin

32. DNA Tertiary Structure • DNA double helical structure coils round histones. • DNA bound to histones formsnucleosomes (10nm fibres) • Nucleosomes contain 146 nucleotides • Nucleosomes • Repeating globular subunits of chromatin that consist of a complex of DNA and histone.

33. Compaction of DNA in a eukaryotic Chromosome

34. Supercoil = coil over coil

35. Functions of DNA and summary of structure • DNA consists of four bases—A, G, C, and T—that are held in linear array by phosphodiester bonds through the 3' and 5' positions of adjacent deoxyribose. • DNA is organized into two strands by the pairing of bases A to T and G to C on complementary strands. These strands form a double helix around a central axis. • The 3 x 109 base pairs of DNA in humans are organized into the haploid complement of 23 chromosomes.

36. Ribonucleic acid (RNA)

37. Ribonucleic acid (RNA) Definition: RNA is polymer of ribonucleotides held together by 3′,5′-phosphodiester bonds. The RNA is made from four types of ribonucleotides, ATP,GTP,CTP and UTP. These ribonucleotides are made from: Nitrogenous bases ; Adenine, Guanine, Uracil and Cytosine. Sugar –ribose Phosphate group

38. RNA Structure • Single stranded but usually forms intra-molecular base pairs • major and minor grooves are less pronounced • Uracil instead of thymine • Structural, adaptor and transfer roles of RNA are all involved in decoding the information carried by DNA

39. Types and functions of RNA • Three major types: • Messenger RNA: 5-10% • Transfer RNA : 10-20% • Ribosomal RNA: 50-80%

40. Minor Types of RNA

41. Messenger RNA (m-RNA) Comprises only 5% of the RNA in the cell Most heterogeneous in size and base sequence All members of the class function as messengers carrying the information in a gene to the protein synthesizing machinery

42. Structural Characteristics of m-RNA The 5’ terminal end is capped by 7- methyl guanosine triphosphate cap. The cap is involved in the recognition of mRNA by the translating machinery It stabilizes m RNA by protecting it from 5’ exonuclease

43. Structural Characteristics of m-RNA The 3’end of most m-RNAs have a polymer of Adenylate residues( 20-250) The tail prevents the attack by 3’ exonucleases Histones and interferons do not contain poly A tails On both 5’ and 3’ end there are non coding sequences which are not translated (NCS) The intervening region between non coding sequences present between 5’ and 3’ end is called coding region. This region encodes for the synthesis of a protein.

44. Structural Characteristics of m-RNA 5’ cap and 3’ tail impart stability to m RNA by protecting from specific exo nucleases.

45. Structural Characteristics of m-RNA The m- RNA molecules are formed with the help of DNA template during the process of transcription. The sequence of nucleotides in m RNA is complementary to the sequence of nucleotides on template DNA. The sequence carried on m -RNA is read in the form of codons. A codon is made up of 3 nucleotides The m-RNA is formed after processing of heterogeneous nuclear RNA

46. Heterogeneous nuclear RNA(hnRNA) In mammalian nuclei , hnRNA is the immediate product of gene transcription The nuclear product is heterogeneous in size (Variable) and is very large. 75 % of hnRNA is degraded in the nucleus, only 25% is processed to mature m RNA

47. Heterogeneous nuclear RNA(hnRNA) Mature m –RNA is formed from primary transcript by capping, tailing, splicing and base modification.

48. Transfer RNA (t- RNA)

49. Transfer RNA (t- RNA) Transfer RNA are the smallest of three major species of RNA molecules They have 74-95 nucleotide residues They transfer the amino acids from cytoplasm to the protein synthesizing machinery, hence the name t RNA. They are also called Adapter molecules, since they act as adapters for the translation of the sequence of nucleotides of the m RNA in to specific amino acids There are at least 20 species of t RNA one corresponding to each of the 20 amino acids required for protein synthesis.

50. Structural characteristics of t- RNA 1) Primary structure- The nucleotide sequence of all the t RNA molecules allows extensive intrastand complimentarity that generates a secondary structure. 2) Secondary structure- Each single t- RNA shows extensive internal base pairing and acquires a clover leaf like structure. The structure is stabilized by hydrogen bonding between the bases and is a consistent feature.