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Lecture 4

Lecture 4 - Different Forms of DNA - BIOL308.pdf

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University of Waterloo
BIOL 308
Bruce Wolff

Lecture 4September1812Different forms of DNABDNAapproximately 10 base pairs per turnTurn is every 34 nmBases are perpendicular to the helix axesRight handedRepresents most of the in vivo DNADNA in cells is mostly B formADNA11 base pairs per turn turns every 28 nm and is right handedShorter and chubbierBases exhibit a tilt with respect to the helix axis 20 degreesFound in low water content dry solutions Lower then normally found in the cellDNARNA and RNARNA helices in a test tube Might exist in vivo as well locally and temporarilyRNA hybrids take on this conformationAlike DNA found in formant spores of BacillusRosalind Franklin focused on this kind of DNA ZDNAFound in test tubes when very high salt concentrationFirst found in dCG polymersAreas of C and Gs12 basepairs per turn turn every 45nm therefore tall and skinny tilt 7 degreesLeft handedRole in reulation of gene expression discovery of proteins with ZDNA binding domainsNew discovery ZDNA in promoter regions of some genesImplicated in chromosomal breakages and large scale deletionsrearrangements in mammals2008 implication in alzheimers diseaseSome promoters are enriched with C and G doublets so Z DNA is involved in regulation of transcription mostly for these important house keeping genesIf you modify cytosine addition of methylmethylated C then it can come at high humidity and low saltTriplehelical DNA HDNA H is for hingeFormed when purines make one strand and pyrimidines make the otherThen the third strand is accomodated in the major grooveRecently found in introns of genes coding for cell membrane proteins as well as proteins involved in phsphorylation signal transduction and development and morphogenesis role in regulation of gene expression NOTES FROM LECTURES Page 1
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