Classify each of the following according to whether it belongs in the x-y, x-o, or z-w system for sex-determination.
a. Ratio of sex chromosomes and autosomal sets determines sex
b. Sry gene causes maleness
c. Insects
d. Mammals
e. Homogametic males
f. Birds
X-Y system =
X-O system =
Z-W system =
