Final answer:
A female with Turner syndrome (XO) has zero Barr bodies in her somatic cells because there is only one X chromosome present and no additional X chromosome requires inactivation.
Step-by-step explanation:
A female with Turner syndrome (XO genotype), having only one X chromosome, would have zero Barr bodies in her somatic cells. In human females with the typical XX genotype, one X chromosome is inactivated during embryonic development to become a Barr body. This process, called X inactivation, ensures that females, like males, have only one functional set of X-linked genes. However, a Turner syndrome phenotype is characterized by a single X chromosome and thus does not require inactivation of any X chromosome. As a result, cells of individuals with Turner syndrome have no Barr bodies, proportional to the number of X chromosomes in excess of one not being present.