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1. Structures and Functions of Nucleic Acids
2. Organization and Content of Genomes
3. DNA Replication
4. The Mutability and Repair of DNA
5. DNA Recombination
6. Transcription and RNA Processing
7. Translation
8. Regulation of Gene Expression
9. Techniques of Molecular Genetics
Introduction to
Molecular Genetics
http://priede.bf.lu.lv/ Studiju materiāli / MolekularasBiologijas / Ievads MolGen / EN
http://priede.bf.lu.lv/ Studiju materiāli / MolekularasBiologijas / Ievads MolGen / EN
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GENOME the complete haploid set of an organism’s DNA
(or the whole genetic information of an organism) divided: physically – into CHROMOSOMES
functionally – into GENES and other elements
CHROMOSOMEa discrete unit of the genome carrying single DNA molecule that contains many genes
GENEa segment of DNA specifying a protein or
noncoding (nc) RNA
DNAthe molecule that encodes genetic
information in all cells[many viruses store the genetic information in the RNA
molecule]
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Prokaryotes typically have one chromosome
Eukaryotes always have many chromosomes
Molecular Biology of the Gene, 5th Edition
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The chromosome content of the HUMAN GENOME
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Eukaryotic organelles also contain genetic information
Genomes, 2nd Edition
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Genome size and gene number roughly correlate with organism’s complexity
(modified)
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Viral genomes are in many forms
A map of the HIV genome
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Bacterial genomes are almost entirely composed of genes
~ 0.2% (9000 bp) of the E. coli chromosome
Genome of E. coli
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Mitochondria have cut-down versions of bacterial genomes
The Human mitochondrial genome: (i) Respiratory complex genes (ii) Ribosomal RNA genes (iii) Transfer
RNA genes
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Gene density is decreased in more complex organisms
Molecular Biology of the Gene, 6th Edition
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The organization of genes on a human chromosome
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The sequence content of the HUMAN GENOME
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Prokaryotic DNA is floating in cytoplasm Eukaryotic DNA is located within nucleus
Molecular Cell Biology, 4th Edition
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In nucleus, DNA is associated with proteins: CHROMATIN
Proteins:• Histones - H1, H2A, H2B, H3, H4• Nonhistone proteins
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Chromosomes exist in distinct states during different phases of the cell cycle
Molecular Biology of the Gene, 5th Edition
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Chromosomes exist in distinct states during different phases of the cell cycle
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Chromosomes have a hierarchic organization
Life The Science of Biology, 7th Edition
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Molecular Biology of the Gene, 5th Edition
The different forms of interphase chromatin
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NUCLEOSOME is the basic unit of eukaryotic chromosome structure
Molecular Biology of the Gene, 5th Edition
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NUCLEOSOME = 2x H2A, H2B, H3, H4 + DNA
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Histones are small, basic proteins that share a common structural motif -
HISTONE FOLD
Molecular Biology of the Gene, 5th Edition
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Molecular Biology of the Gene, 5th Edition
Histone folds bind to each other mediating THE ASSEMBLY OF
NUCLEOSOMES
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Higher order chromatin structure: 10-nm fiber is packed into 30-nm fiber
6-fold compacting 40-fold compacting
Molecular Biology of the Gene, 5th Edition
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Linker histone H1 and tails of the core histones act to form the 30-nm fiber
Molecular Biology of the Gene, 6th Edition
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Further compaction involves large loops of 30-nm fiber
1000-fold compacting
Molecular Biology of the Gene, 5th Edition
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Interphase chromosomes are ‘fluid’ - REGULATION of chromatin structure
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Structure and positioning of nucleosomes is determined by non-histone proteins
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Types of changes in chromatin during transcription initiation
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Histone modifications alter the ‘meaning’ of chromatin
Recombinant DNA, 3rd Edition
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Specific meanings of the histone modifications: HISTONE CODE
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There are two types of interphase chromatin
1. Euchromatin– the ‘usual ‘ form– contains (potentially) active genes
2. Heterochromatin– more condensed form– additional proteins (HP1)
– constitutive• no genes• feature of all cells• e.g., centromeric, telomeric DNA
– facultative• in some cells some of the time• inactive genes
Molecular Biology of the Cell, 5th Edition
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Mitotic chromosomes are formed from chromatin in its most condensed form
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Each chromosome has a characteristic banding pattern
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Each eukaryotic chromosome has one centromere, two telomeres and many origins of replication (ori)
Molecular Biology of the Gene, 5th Edition