1.Intro and Genome Composition-1
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Transcript of 1.Intro and Genome Composition-1
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Genetics and Molecular Biology (Basic)- Course Outline
Genome composition
Organization of the genome,Coding and non-coding sequences,
Regulatory elements, repeat sequences, transposons, organelle genomes
Chromosome structure and function
Packaging of DNA into the nucleus, nucleosomes,
Chromosome features-centromeres, telomeres, chromosome segregation
in mitosis and meiosis
DNA replication
DNA polymerases, mechanism of replication,
Replication of damaged DNA, termination
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Mutations
Sources of mutations, types of mutational events,Methods to detect mutations, mutations and disease)
DNA Repair
DNA damage response, Mismatch repair, Base Excision repair,Nucleotide Excision repair, Double strand break repair
DNA Recombination
Recombination models, Recombination proteins, Gene conversion,
Homologous Recombination, DNA recombination and chromosome segregation
Genetics and Molecular Biology (Basic)- Course Outline
Suggested Reading: Genes IX (Benjamin Lewis)
Molecular Biology of the Gene (Watson et al.,)DNA Mutagenesis and Repair (Friedberg)
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Genome sizes vary considerably between different species
Genome size basepairs
Genes IX (Benjamin Lewis)
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Genome organization and size varies between organisms
Genes IX (Benjamin Lewis)
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Complex genomes have considerable non-coding DNA
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C value paradox
C value- The total amount of DNA in the haploid genome
- Excess DNA compared to the number of proteins the genome codes for- No correlation between C value and morphological complexity
DNA reassociation analysis (CoT analysis)
- Important approach for studying genome complexity.- Total genomic DNA is first fragmented to a relatively small size
- The DNA is then denatured and allowed to renature by gradual
reductions in temperature. This reveals different 'Cot' values, which are
the product of the DNA concentration in moles per litre (Co) and the
reassociation time in seconds (t),
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DNA reassociation analysis
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Estimate fraction of reassociated DNA
Double stranded DNA has higher affinity for a crystalline form of Calcium Phosphate
Hydroxyapatite. Both ssDNA and dsDNA can be washed off and estimated separately
http://www.learnerstv.com/animation
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DNA from calf reassociated faster than E.coli DNA!
Extent of reassociation is measured by chromatographic techniques and
plotted against Cot
Calf thymus DNA reassociate as different fragment -fast, median and slow,E.coli DNA behaves mostly as slow component.
DNA reassociation analysis for simple versus complex DNA
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Cot1/2value is a measure of the Genome complexity
Co- 12pg, Bacterial DNA- 0.004pg, Mammalian 3pg
3000 copies of the Bacterial DNA compared to only 4 of the mamalian DNA
(750 fold difference) Either increase concentration or time by 750 fold to get
same Cot1/2
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Utility of Cot analysis
Information on unique sequence content (number of genes)
How much of the DNA is repetitive
Phylogenetic relationships among different organisms
Modern methods for genome complexity analysis
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Highly repetitive, moderately repetitive and Non-
repetitive DNA comprise the Eukaryotic genome
25%
30%
45%
Genes IX (Benjamin Lewis)