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Gene and Chromosome. DNA is the genetic material.

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Presentation on theme: "Gene and Chromosome. DNA is the genetic material."— Presentation transcript:

1 Gene and Chromosome

2 DNA is the genetic material

3 Genes and Chromosome Molecular Definition of Gene the structure and function of DNA The global structure of chromosomes Organelle DNA

4 Molecular Definition of Gene The entire nucleic acid sequence that is necessary for the synthesis of a functional protein and RNA Coding region (exon and intron) + Regulatory sequences (e.g. promotor, enhancer, polyadenylation site, splicing sites) There are also tRNA and rRNA genes

5 Gene & Protein

6 Baterial Operon and Simple Eukaryotic Transcription Unit

7 Complex Eukaryotic Transcription Complex

8 The Structure and Function of DNA A DNA molecule consists of two complementary chains of nucleotides The structure of DNA provides a mechanism for heredity

9 Structure and Composition of DNA & RNA

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17 The DNA double helix

18 DNA is a template for its own duplication

19 The Global Structure of Chromosome Nucleotides --> DNA --> Gene --> Chromosome --> Genome Human DNA is ~ 2 meters long. The nucleus of DNA is about 6 µM in diameter. Specialized proteins bind to and fold DNA into coils and loops, providing higher level of organization. Although DNA is tightly packed, it can be easily accessed by many enzymes that replicate, repair or express its genes.

20 Nucleus

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22 A Karyotype of Human Chromosomes

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24 Normal & Aberrant Chromosome

25 Organization of Genes on Human Chromosome

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27 Content of the Human Genome

28 Interface / Mitotic Chromosome

29 Chromatin Packing

30 Nucleosomes

31 Structural Organization of the Nucleosome

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34 Organization of the Core Histones

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37 Chromosome Remodeling ATP-driven chromatin remodeling machines change nucleosome structure Covalent modification of the histone tails can profoundly affect chromatin

38 Irregularities in Chromatin Structure

39 A role Histone H1 in remodeling Chromosome structure

40 Histone Tails

41 Mechanism of Chromatin Remodeling Complex

42 Cycle of Chromosome Remodeling

43 Covalent Modifications of Histone Tails

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45 Heterochromatin/Euchromatin There are two types of chromatin in interface, heterochromatin and euchromatin Heterochromatin is a highly condensed, and organized 10% of the genome is packed into heterochromatin Heterochromatin is resistant to gene expression Heterochromatin is concentrated in specific regions e.g. centromeres and telomeres

46 Organelle DNA Mitochondria and Chloroplast DNA Exhibit cytoplasmic inheritance Encode rRNA, tRNA, and some mitochondrial proteins Product of mitochondrial genes are not exported Mitochondrial gene codes differ from the standard nuclear code

47 DNA Replication, Repair, and Recombination

48 Eukaryotic Cell Cycle

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50 DNA Replication DNA Polymerase Replication Fork –DNA polymerase- Sliding Ring –DNA primase- Single-strand binding protein –DNA helicase DNA polymerization in 5’-3’ direction –Leading strand –Lagging strand Proofreading mechanisms DNA Topoisomerase

51 DNA Double Helix is the Template

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53 Mg2+ is required for polymerization

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55 DNA Polymerase

56 DNA replication is semiconservative

57 DNA Replication of a Circular Chromosome

58 Replication Fork

59 Why only 5’--> 3’ Direction ?

60 Why only 5’--> 3’ Direction? For High Fidelity DNA Synthesis

61 5’- 3’ Polymerization 3’- 5’ Exonucleolytic Proofreading Strand-directed mismatch repair

62 Editing by DNA Polymerase

63 Exonucleolytic Proofreading by DNA Polymerase

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65 5’- 3’ Direction is Energy Efficient

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68 DNA Synthesis of the Lagging Strand

69 RNA Primer Synthesis

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72 Other Enzymes & Proteins in DNA Replication

73 DNA Ligase

74 Bacterial Replication Fork

75 Mammalian Replication Fork

76 DNA Helicase

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78 SSB

79 Single-Strand DNA-Binding Protein (SSB)

80 Sliding Clamp for DNA polymerase

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82 Sliding Clamp

83 Moving Replication Fork

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86 Mismatch Proofreading Proteins

87 DNA Topoisomerase

88 Winding Problem

89 DNA Topoisomerase I

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91 DNA Topoisomerase II = DNA Gyrase

92 DNA Topoisomerase II

93 The Initiation and Completion of DNA Replication in Chromosome

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95 DNA Replication in Bacteria

96 Refractory period for DNA initiation

97 Eukaryotic Chromosome Contains Multiple Origin of Replication

98 Identification of yeast origin of replication

99 Eukaryotic Origin of Replication Last multisubunit complex(ORC; origin recognition complex) binds to eukaryotic origin of replication All yeast Origin of replication has been identified (about 150 nucleotide pairs) The mammalian origin of replication sequence is difficult to identify

100 Yeast Origin of Replication

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103 Telomere

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109 DNA Repair

110 Spontaneous Alterations

111 Depurination and Deammination

112 Thymine Dimer

113 Deamintation

114 Depurination

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120 Double-Strand Break Repair

121 DNA Recombination

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125 Junction

126 ssDNA Hybridization

127 Rec A in Homologous Recombinaton at DNA Synapsis

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130 Holiday Junction

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133 Resolving Holiday Junction

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137 General Recombination in Mitotic and Meiotic Cells

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139 Site Specific Recombination Moving of mobile genetic elements between non-homologous DNA Transpositional site-specific recombination –DNA only transposition Cut and Pase transposition Replicative transposition –Retroviral-like retrotransposition –Nonretroviral retrotransposition Conservative site-specific recombination

140 Bacterial Transposons

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143 Cut-and-Paste Transposition

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145 Replicative Transposon

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147 Retrovirus

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150 Site-specific recombintaion by a retro virus or a retrovirus-like retrotransposon

151 Nonretroviral Retrotransposon

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153 Conservative site specific recombination

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