Lecture-9-DNA-modification- epigenetics

Inactivatedxchromosomebarrbody

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Unformatted text preview: finactivation •  X ­‑inactivation –  Dosagecompensation –  Maintainsequivalencybetweenmalesandfemales ­‑X ­‑linkedgenes. •  Geneticimprinting –  Heritablechromatinstatesbasedonparentalorigin –  Mixingofparentalgenomes 18 EpigeneticRegulation •  EpigeneticInheritance= –  Aheritablealterationofgenesorchromosomes –  WithoutchangesinDNAsequence 19 Positioneffectvariegation Heterochromatininducedgenesilencingofneighboringgenes 20 PositionEffectVareigation 21 X ­‑Inactivation •  AmechanismforDOSAGECOMPENSATION –  –  –  •  Somaticcells –  –  –  –  •  Femaleswith2Xchromosomes makethesameamountofmRNA asmaleswith1Xchromosome Allfemalecells RandominactivationofoneofthetwoXchromosomes Earlystageinembryonicdevelopment Propagatedtoallprogenycells Germlinecells –  InactiveX ­‑chromosomeisREACTIVATED 22 X ­‑inactivation •  InactivatedX ­‑chromosome ­‑BARRBODY •  MajorityofthegenesoninactiveX ­‑SILENCED •  RegulatedbyXistwhich –  makesanon ­‑codingRNA –  convertspreviously OPENCHROMATIN into CLOSED CHROMATIN . –...
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