All of the following statements are correct except
a) Tropheryma whipplei could be identified before it had been grown in culture.
b) the GC content of DNA can be measured by determining the temperature at which double-stranded DNA melts.
c) sequence differences between organisms can be used to assess their relatedness.
d) based on DNA homology studies, members of the genus Shigella should be in the same species as Escherichia coli.
e) gel electrophoresis is used to determine the serotype of an organism.