All of the following statement(s) is/are true except:
Ans: A (Denever...) Denver ClassificationThe classification of human CHROMOSOMES on the basis of size and centromere position; the 23 pairs of chromosomes areclassifted in seven groups (A to G), in order of decreasing length. Used before it was possible to distinguish among thechromosomes of the groupsCHROMOSOME GROUP (Arranged in the following order in karyotype)ChromosomesLocation Of CentromereA1-3MetacentricB4-5SubmetacentricD13-15AcrocentricF19-20MetacentricG21-22, YAcrocentricE16-1816- Metacentric 17,18- SubmetacentricC6-12, XSubmetacentric MetacentricSubmetacentricAcrocentricGroup A. E (16). FGroup B, C, E (17,18)Group D, G " Lyon hypothesis: It states that (1) only one of the X chromosomes is genetically active, (2) the other X of either maternal or paternal origin undergoes heteropyknosis anti is rendered inactive, (3] inactivation of either the maternal or paternal X occurs at random among all the cells of the blastocyst on or about the 16 th day of embryonic life, and (4) inactivation of the same X chromosome persists in all the cells derived from each precursor cell. Thus, the great preponderance of normal females are in reality mosaics and have two populations of cells, one with an inactivated maternal X and the other with an inactivated paternal X. Herein lies the explanation of why females have the same dosage of X-linked active genes as have males. The inactive X can be seen in the interphase nucleus as a darkly staining small mass in contact with the nuclear membrane known as the Barr body, or Ar chromatin"-Robbins 8th/164X-INACTIVATION Harrison 18th/515;17th/411In normal females one of the chromosomes undergoes X inactivationin somatic cells.The inactivation ofthe paternal or maternal X chromosome occurs randomly in each somatic cell and thereby serves as a mechanism of dosage compensation, ensuring that males and females have equal expression of most X-linked genes.Some genes on the X chromosome "escape" the inactivating mechanism and are expressed from both X chromosomes.In disorders such as Klinefelter syndrome, some genes may be expressed from both X chromosomes, resulting in its phenotypic features.
Denever group F-contain X chromosome
Denever group C- contain X chromosome
Denever group G- contain acrocentric chromosome
Bar body is inactive X chromosome
Cytogenetic Disorders