PUC Vikasana Program- 2012

Transcription

1 Chromosome Nucleus DNA PUC Vikasana Program- 2012

2 Introduction Molecular biology is the study of biology at a molecular level. Macromolecules and the macromolecular mechanisms. Interactions between the various systems of a cell, including the interactions between DNA, RNA and protein biosynthesis. 2

3 One Mark Questions 3

4 1.1. What is a gene? A gene may be defined as a functional portion of DNA molecule with specific sequences of nucleotides and producing a particular character or trait. 4

5 1.2. Define Cistron. A segment of DNA molecule responsible for specifying one polypeptide or protein chain. 5

6 1.3. What is muton? This is a unit within a cistron capable of undergoing g gene mutation. 6

7 1.4. Define recon. This is the smallest unit of DNA comprising a single nucleotide or nucleotide pair undergoing recombination. 7

8 1.5. Name the scientist, who isolated DNA for the first time? Friedrich Miescher 8

9 1.6. What is a nucleoside? The nitrogenous base and the pentose sugar together constitute a nucleoside. 9

10 1.7. What is a nucleotide? A nucleotide is a unit of nucleic acids and is composed of a nitrogenous base pentose sugar and phosphate. or nucleoside + phosphate. 10

11 1.8. Name the chemical bond formed between nitrogenous base and pentose sugar in a nucleotide. N,β-Glycosidicβ bond. 11

12 1.9. Name the chemical bond formed between pentose sugar and phosphate group in a nucleotide. Phosphodiester bond. 12

13 1.10. Name the chemical bonds formed between the complementary nitrogenous bases in DNA. Hydrogen bond. 13

14 1.11. How many nucleotide pairs are present in one complete turn of DNA helix? Ten base pairs 14

15 1.12. What is the percentage of adenine in a double stranded DNA, having 30% of cytosine? 20% 15

16 1.13. Mention the functions of Unwindase. Unwindining the two strands of DNA molecule during protein synthesis. 16

17 1.14. What is the function of gyrase? Gyrase relieves the tension of super coiled regions of DNA 17

18 1.15. What is the function of DNA ligase? DNA ligase joins the fragments of DNA. 18

19 1.16. What is a lagging strand of DNA? It is the strand of DNA formed discontinuously against the sense strand during replication. 19

20 1.17. What is a leading strand of DNA? It is the daughter strand of DNA formed continuously towards the replication fork during replication. 20

21 1.18. What is ORI site? The point at which h the uncoiling of DNA begins during replication is called ORI site. 21

22 1.19. What are Okazaki fragments? Short single stranded discontinuous DNA fragments formed away from the replication fork during replication 22

23 1.20. What is RNA primer? It is a short fragment of RNA formed by RNA primase at the beginning of DNA replication. 23

24 1.21. Name the short lived RNA. mrna 24

25 1.22. Name the scientist who proposed the clover leaf model of trna. Robert.W.Holley. WH 25

26 1.23. Which is the amino acid binding site of trna? CCA-end or 3 -OH end of trna. 26

27 1.24. Which is the decoding site of trna? Anticodon site or NODOC 27

28 1.25. Mention the functions of trna. It transfers amino acid to the site of protein synthesis. 28

29 1.26. Mention one function of mrna. It carries the genetic message from DNA in the form of codons for the synthesis of a polypeptide or protein chain. 29

30 1.27. Mention one function of rrna. It is a structural component of ribosomes that helps in translation process of protein synthesis. 30

31 1.28. Which part of the trna is recognized by AA-tRNA synthetase enzyme? DHU loop / Dihydroxy Uridine loop 31

32 1.29. What is monocistronic mrna? The mrna transcribed by a single cistron or The mrna that carries codes for a single polypeptide. 32

33 1.30. What is polycistronic mrna? The mrna transcribed from many cistrons. 33

34 1.31.What is heterogenous nuclear RNA? The RNA transcribed by eukaryotic gene having coding exons and non coding introns. 34

35 1.32. What are split genes? The genes having coding exons and non-coding introns 35

36 1.33. Define replicon. It is a unit of DNA that undergoes replication. 36

37 1.34. What is a operon? It is a coordinated assembly of regulatory and structural genes meant tto perform a specific metabolic activity. 37

38 1.35. Define codon. A unit of three nucleotides on mrna that codes for a specific amino acid during protein synthesis. 38

39 1.36. What is anticodon? A unit of three nucleotides on trna that decodes the codon of mrna. 39

40 1.37. Define initiator codon. The codon on mrna where the formation of polypeptide is initiated. 40

41 1.38. Name the initiator codon. AUG 41

42 1.39. Which amino acid is coded by initiator codon? Methionine 42

43 1.40. Name the enzyme that activates amino acid during protein synthesis. Aminoacyl trna synthetase. 43

44 1.41. Define transcription. The process of formation of mrna or other types RNAs from the antisense strand of DNA with the help of RNA polymerase. 44

45 1.42. Define translation. The process of decoding of codons on mrna into a sequence of amino acid forming a polypeptide chain. 45

46 1.43. Which gene of operon produces the repressor protein? Regulator gene. 46

47 1.44. Which enzyme catalyses the synthesis of DNA using a RNA template? Reverse transcriptase. 47

48 1.45. Name the inducer of Lac-operon in E.Coli. EColi Lactose 48

49 1.46. Name the scientists who proposed operon concept. Jacob and Monod 49

50 1.47. Name the enzyme that helps in the formation of peptide bonds between amino acids. Peptidyl transferase 50

51 1.48. Name the enzyme coded by Lac-Z gene. β-galactosidase 51

52 1.49. Name the enzyme coded by Lac-Y gene. β-galactoside permease 52

53 1.50. Why is G-C Pairing stronger than A-T Pairing? 3 Hydrogen bonds bind G-C pairing, Where as there are 2 Hydrogen bonds present in A-T pairing. 53

54 Two Mark Questions 54

55 2.1 Name any two types of RNA in a eukaryotic cell. mrna trna rrna 55

56 2.2 List four functions of RNA. Genetic RNA carries genetic characters in RNA virus. mrna carries the message from DNA in the form of triplet codons. Continued... 56

57 2.2 Four functions of RNA (Continued). trna carries specific amino acids to the site of protein synthesis. rrna helps in binding of mrna and trna to the ribosomal surface. 57

58 2.3 Mention two structural and two control genes of lac operon. Structural genes are Lac-Z, Lac-Y and Lac-A. Control genes are Regulator(R), Promoter (P) and Operator (O). 58

59 2.4 Mention any four characteristic features of genetic code. Genetic code consists of triplet codons. Genetic code is unambiguous. Genetic code is universal Genetic code is degenerate. AUG is the initiator codon. Continued... 59

60 2.4 Genetic code characters (Continued). Genetic code is comma less. 61 out of 64 codons code for amino acids. Three codons are terminator codons - UAA, UAG, UGA. 60

61 2.5 What are terminator codons? Mention two of them. The codons that terminate the polypeptide chain synthesis are called terminator codons. UAA, UAG, UGA. 61

62 2.6 Name the pyrimidines present in DNA. Cytosine and thymine. 62

63 2.7 Name the pyrimidines present in RNA. Cytosine and uracil 63

64 28Mention 2.8 any four functional differences between DNA and RNA. DNA RNA It is a hereditary material It is a hereditary material in a few viruses It is self replicating It is synthesized against a DNA template. It directs protein It assists in protein synthesis synthesis It can produce DNA and It usually does not RNA produce DNA 64

65 2.9 Name the nitrogenous bases of DNA. Adenine,Guanine, Cytosine and Thymine. 65

66 2.10 Name the nitrogenous bases of RNA. Adenine, Guanine, Cytosine and Uracil 66

67 2.11 List two differences between a nucleotide and a nucleoside. NUCLEOTIDE NUCLEOSIDE It is made up of It is made up of nitrogenous base, nitrogenous base, pentose sugar and pentose sugar. phosphate h It is acidic in nature It is alkaline 67

68 212M 2.12 Mention two differences between prokaryotic and eukaryotic genes. PROKARYOTIC GENE It transcribes poly cistronic mrna Unsplit gene Only exons. EUKARYOTIC GENE It transcribes mono cistronic mrna Split gene Introns and exons 68

69 2.13 Explain the two steps in the activation of amino acid during protein synthesis. Amino acid + ATP Aminoacyl aminoacyl + PP synthetase adenylate Aminoacyl + trna Adenylate aminoacyl trna+amp 69

70 2.14 List four functions of DNA. It is the genetic material. It is the master molecule of metabolic activities as it contains codes for all the proteins. It shows autocatalytic t ti function. It can undergo mutations. It synthesizes different types of RNA by transcription 70

71 2.15 Draw a labelled diagram of trna molecule. 71

72 Five Mark Questions 72

73 3.1 Describe the double helical model of DNA with a labelled diagram 73

74 3.1 About DNA : Two DNA strands are anti parallel. Strands are complementary. 2 strands are helically coiled. 2 polynucleotide strands are present. Back bone formed by deoxy ribose sugar and phosphate groups held together by the Phosphodiester bond. Continued... 74

75 3.1 About DNA (Continued) : The complementary base pairing A=T,C G between the helices is by hydrogen bonds. One turn consists sts of 10 base pairs and measures 34A. 75

76 3.2 Explain the experiment of O.T. Avery that proved DNA as the genetic material. 76

77 3.2 DNA as genetic material : When living Streptococcus pneumoniae S strain injected mouse dies. Living R Strain injected mouse remains healthy. Kill the virulent S Strain by heating injected to the mouse, remains healthy. Continued... 77

78 3.2 DNA as genetic material (Continued) : Mix dead S strain with living R strain is injected, mouse dies. Conclusion is that chemical substance from one cell is capable of genetically transforming to another cell. Material when treated with DNAse, RNAse, Proteases separately further confirms DNA is genetic material. 78

79 33Describe 3.3 the clover leaf model of trna molecule with a neat labelled diagram. 79

80 3.33 Structure of trna Tri foliate. 3 -OH end having terminal nucleotides CCA. 5 end ends in G. Tψ C loop. DHU loop. Anti codon loop. Variable short arm. 80

81 3.4 Explain the semi conservative replication of DNA molecule with the help of labelled diagram. 81

82 34DNA 3.4 Replication : Origin of replication at ORI site. Unwinding by the enzyme unwindase. SSBP destabilises the strands and stress is relieved in super coiled regions by gyrase. Replication fork is formed the separated strands act as template strand. Continued... 82

83 3.4 DNA Replication (Continued) : Priming a short sequence of 5-10 nucleotides with a free 3 -OH end called as RNA primer takes place by RNA primase. Leading strand formation towards replication fork. Enzyme involved is DNA polymerase III. Continued... 83

84 3.4 DNA Replication (Continued) : In the lagging strand 5-3 template synthesis is discontinuous and occurs as Okazaki fragments away from replication fork. DNA polymerase I replaces RNA primer with DNA nucleotide. Continued... 84

85 3.4 DNA Replication (Continued) : DNA fragments are joined by DNA ligase. Proofing of strands done by DNA polymerase II. Winding of parental strands with lagging leading strands to produce 2 similar daughter molecules by the enzyme windase. 85

86 3.5 Explain amino acid activation and chain initiation steps of protein biosynthesis. Amino acid + ATP Aminoacyl aminoacyl + PP synthetase adenylate Aminoacyl + trna aminoacyl trna+amp Adenylate 86

87 3.5 Details of initiation Chain Initiation Binding of smaller sub unit of ribosomes to 5 end of mrna. Binding of methionine trna to the initiating codon of mrna with the help of IF1, IF2, IF3 and ATP. Attachment of larger sub unit of ribosome. 87

88 36Explain 3.6 chain elongation and chain termination process of translation. continued... 88

89 3.6 Translation AA-tRNA-complex is at the A site of the 50s ribosome. The A site is the aminoacyl trna binding site In prokaryotes the AUG codon of mrna stands for the amino acid methionine. There is relative movement of ribosome and mrna. AUG moves on to P site. continued... 89

90 3.6 Translation (Continued) : The amino acid is left at this site and trna moves out. GTP is required to this. Second codon is in A site. AA2-tRNA complex with second AA is attached to this codon. 2 nd codon moves to the Psite. AA1 attached to AA2 at the P site. continued... 90

91 3.6 Translation (Continued) : 2 nd trna moves out to the E site. Termination. Presence of one of the terminating ti codon brings about termination. UAA,UAG,UGA are terminator codon. Poly ypeptide p chain is released. 91

92 3.7 Mention the genes of Lac-Operon and their functions continued... 92

93 Genes of Lac-Operon Switch on : Operator gene get active in presence of lactose. Lactose is regarded as inducer Switch on state of the operon is through repressor protein, When binds to lactose. Now it fails to bind to operator. Hence operator gene ZYA active transcription ti takes place Continued 93

94 Genes of Lac-Operon (Continued) : Translation results in 3 enzymes, transcription is by mrna polymerase. Switch off : Lactose absent repressor protein binds to operator. mrna polymerase can not slide through operator. Transcription and enzyme synthesis can not take place. 94

95 Question Paper : Distribution of Marks Sections in question paper Marks Number of questions Botany Part A Questions to be answered Section A Marks Section B Section C Section D Practical Syllabus Zoology Part B Section E Section F Section G Section H Practical Syllabus Total 90 95

96 Unit Weightage marks Distribution Units Weightage of Marks Total Molecular Biology 1or 2 1 or 2 1 out of 2 10 Biotechnology 1 or 2 2 or 3 1 out of 2 12 Plant histology & Anatomy 1 or Plantwater relations 1 or Bioenergetics 1 or out of 2 12 Growth 1 or Botany Practicals 2 10 Genetics 1 1 or Biodiversity out of 2 11 Man in health and diseases 5 2 or 3 2 out of 3 28 Continuity of life Zoology Practicals 2 10 Total

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