Barr body

Barr body (named after discoverer Murray Barr) or X-chromatin is an inactive X chromosome in a cell with more than one X chromosome, rendered inactive in a process called lyonization, in species with XY sex-determination (including humans). The Lyon hypothesis states that in cells with multiple X chromosomes, all but one are inactivated during mammalian embryogenesis.[3] This happens early in embryonic development at random in mammals, except in marsupials and in some extra-embryonic tissues of some placental mammals, in which the X chromosome from the sperm is always deactivated. In humans with euploidy, a genotypical female (46, XX karyotype) has one Barr body per somatic cell nucleus, while a genotypical male (46, XY) has none. The Barr body can be seen in the interphase nucleus as a darkly staining small mass in contact with the nucleus membrane. Barr bodies can be seen in neutrophils at the rim of the nucleus. In humans with more than one X chromosome, the number of Barr bodies visible at interphase is always one fewer than the total number of X chromosomes. For example, people with Klinefelter syndrome (47, XXY) have a single Barr body, and people with a 47, XXX karyotype have two Barr bodies. Question: How many Barr bodies would you expect to see in a human cell containing the following chromosomes? A) XX B) XY C) XO D) XXY E) XXYY F) XXXY G) XYY H) XXX I) XXXX #NikolaysGeneticsLessons #BarrBody #Genetics #Chromosome #karyotype #KevinTokoph #tokoph #catalystUniversity #biology #biochemistry #physiology #XChromosome #yChromosome #geneSilencing #egg #sperm #XlinkedTraits #xChromosomeInactivation #lyonisation #DosageCompensation #barrBodyFromCheekEpithelialCells #barrBodyFromWhiteBloodCellsWBCs #drumstickBarrBody #neutrophilBarrBody #barrBodyTemporarySlideMount #acetocarmine #barrBodySlidePreparation