Jan17_introDNA_Mod1_2

Jan17_introDNA_Mod1_2 - Module 1 Introduction DNA as an...

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Module 1 Introduction “DNA as an analyte” continued
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Key words DNA as an analyte Nucleotide – Nucleoside H-bond = hybridization Hybridization = baseparing Number of nucleotides = Number of basepairs C value
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3 ‘Ploidy’ is the number of homologous sets of chromosomes in a biological cell (particularly for somatic cells) Number of cells used in the measurement/calculation The relationship between the mass weight and nucleic acids: 1pg = 1 x 10 9 bp (double-stranded DNA) We need the following information to calculate the genome size.
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4 Example: calculation of a genome size How big is the genome size of an diploid organism, if we can extract and obtain one microgram of DNA from 10 6 harvested cells? 1μg/10 6 cells = 1pg DNA/ one cell 1pg DNA /cell/two sets of chromosome one set of chromosome (haploid) or one gamete has 0.5pg DNA Knowing that 1pg = 1 X 10 9 pb Thus one gamete DNA of 0.5pg = 0.5 Χ 10 9 bp Thus this organism has the genome size of 5 X 10 8 pb
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Logical expectation of c-value Total number of genes absolutely essential for a structure to be called life, which should exhibit growth, reproduction and live in happiest times and able to produce a population Organism with more types of cells and complexity of cell types more and more number of genes are required Greater number functions, regulations, adaptations and various other devises in the mode of living and reproduction, one generally expect to have acquired greater number of genes, so the genomic size.
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Mycoplasma 10 5 - 10 6 bp Gram negative bacteria 5 x 10 6 bp Gram positive bacteria 2 to 8 x 10 6 bp Fungi 2 to 5 x 10 7 bp Algae 5 to 8 x 10 7 bp Molds 6 to 9 x 10 7 bp, Worms 7 x 10 7 to 2 x 10 8 bp Molluscs 6 x 10 8 to 7 x 10 9 bp Insects 1.5 x 10 8 to 6 x 10 9 bp Echinoderms 5 x 10 8 to 5 x 10 9 bp Cartilage fishes 3 x 10 9 to 8 x 10 9 bp Bony fishes 6 x 10 8 to 9 x 10 9 bp Amphibians 8 x 10 8 to 9 x 10 11 bp Reptiles 2 x 10 9 to 5 x 10 9 bp Birds 2 x 10 9 to 9 x 10 9 bp Mammals 3 x 10 9 to 5 x 10 9 bp Flowering plants 8 x 10 8 to 2 x 10 12 bp
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7 C –value Paradox Expectedly, logic wise, as the body of an organism becomes more and more complex, the size of the genome should increase according to the complexity. Not quite true!
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Explanation for C-value paradox More types of cells, more complexity of cell types, more and more number of genes Not all DNA is actually used for coding a gene Some of DNA is duplicated Each gene could have many copies in a cell Some part of nuclear DNA does not have any function
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Qualitative technique to test the hypotheses that were developed to explain the C-paradox Based on the physico-chemical properties of DNA H-bonding between two complementary strands Destroy under high temperature <==> restore when cooling down Destroy under high pH (alkaline conditions) <==>
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Jan17_introDNA_Mod1_2 - Module 1 Introduction DNA as an...

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