fall 09 lecture 05

fall 09 lecture 05 - If a genome does not contain...

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Reassociation is inversely proportional to the genome (DNA) size . The DNA sources are: a synthetic DNA duplex of poly A and poly U polynucleotide chains; mouse satellite DNA , a fraction of mouse DNA in which the same sequence is repeated many thousands of times; MS2 DNA (bacteriophage); T4 DNA (more complex bacteriophage then MS-2); E. coli DNA; calf DNA-nonrepetitive fraction (highly repetitive DNA fraction was removed). (adapted from Britten, R. J., and Kohne, D. E., 1968. Science 161: 529– 540.) If a genome does not contain repetitive sequences (for example, MS2, T4 and E. coli genomes), the complexity of the genome (expressed in # of nucleotides) is (theoretically) the same as the genome size Lewin, Genes VIII)
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E. Coli Genome vs. Calf Genome Keep in mind: 0% reassociated (ds) DNA is the same as 100% denatured (ss) DNA everything is still ss E. Coli : no repetitive sequences; the whole genome is one unique sequence Difficult for sequences to find complementary sequences Once they are found – fast re-association Calf: lots of repetitive sequences – fast re- association Some sequences unique – slow re-association at the beginning but gets faster (those unique sequences resemble/are comparable to E. coli genome) fast middle slow
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: there is lots of them (1000-100000), they are able to find each other really easylly fast renaturation . Role unknown. Moderately repetitive : moderate # (10-1000), find each other with little difficulties, need more time middle renaturation . Some of them lack coding function. Some of them – code for different gene families: globin genes, immunoglobulin genes, genes for tRNAs and rRNAs etc. Unique : one to few copies, have lots of difficulties to find each other during renaturation slow renaturation . Mostly protein coding sequences. slow
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This note was uploaded on 07/10/2010 for the course BIOL 308 taught by Professor Miskovic during the Fall '09 term at Waterloo.

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fall 09 lecture 05 - If a genome does not contain...

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