Answer:
Barr body may be defined as the one of the inactive X chromsome of the human female. The human female consists of XX chromosome whereas XY in male. To compensate the extra X chromosome in female one of the X chromosome become inactive and known as barr body. The barr body is found in the somatic cells.
Lyon hypothesis:
Lyon hypothesis states that dosage compensation occur in human females by the random inactivation of one of the X chromosome. The inactivated X chromosome is named as barr body. The lyon hypothesis was given by Mary Lyon.