Lecture-9-DNA-modification- epigenetics

pwsgene paternallyexpressed maternallyimprinted x

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Unformatted text preview: felterMalesarenot PhenotypicallyNormal •  Not all genes on the inac7ve X is silent •  Some genes escape inac7va7on. 33 X ­‑chromosomeimbalances –  XXY–Kleinfelter ssyndrome •  Tallmales,mildlyimpairedIQ •  Sterilesincethesexchromosomesaretri ­‑valentduringmetaphase. –  XYY •  Predispositiontowardviolentbehavior •  FertileduetonormalpairingbetweenXandYduringmetaphase. •  GameteshaveanXorYneverXYorYYthereforeconditionisnotpasseddownto progenyandgametesarenormal. –  XXX •  Phenotypicallynormal •  Fertile,pairingbetween2ofthe3Xsresultinginnormalgametes •  Theconditionisnotpasseddowntoprogeny. –  XO–Turnersyndrome •  Reducedviability •  SterilesinceXhasnothingtopairwith •  phenotypeduetosingledosagefromgeneswhichescapeX ­‑inactivationandthereforeare typicallyneededintwodosesfornormalfunction. OtherSexChromosomeImbalances •  47,XYYmales  ­‑  Veryslightphenotypiceffects.Tendtobetallandarecompletely fertile.  ­‑  Haveincreasedriskofeducationalandbehavioraldisorders(slightly loweraverageIQ;ADD) •  47,XXX;48XXXX;49XXXXXfemales  ­‑  Trisomicfemaleshavenearnormalphenotypes,butmanyhave learningproblems.  ­‑  Tetrasomicandpentasomicfemaleshavemoreseverephysicaland mentalretardation. GeneticImprinting •  Epigeneticsilencingofchromosomalregionsonlyinone parent •  Paternallyimprintedgenes –  Silentonchromosomeinheritedfromthefather –  Expressed...
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