Answer:
D. One cannot test the Lyon hypothesis with homozygous X-linked genes because the test requires identification of allelic alternatives to see differences in X chromosome activity.
Step-by-step explanation:
Lyon hypothesis explains dosage compensation in mammals with XX-XY type of sex determination. The human females have two copies of X chromosomes while human males have only one copy of the X chromosome.
To balance the number of X linked genes between males and females, one X chromosome in all the somatic cells of a human female is inactivated during early embryonic development and is a presence in form of Barr body.
The inactivation of the X chromosome is random and either maternal or paternal X chromosome from a cell of a human female can be inactivated.
To observe the Lyon hypothesis, the expression of X linked genes is observed. For the purpose, the female should be heterozygous for a particular X linked gene to observe the expression of different alleles in her cells due to random inactivation of either of the X chromosome.
A human female with a homozygous X linked gene would express the same allele of the gene in all of her cells irrespective of the inactivation of the paternal or maternal X chromosome.