What is the basic mechanism by which trithorax and Polycomb complexes maintain established patterns of Hox gene expression throughout the remainder of embryonic development?
a. They encode transcription factors that regulate Hox gene expression.
b. They regulate patterns of histone methylation to keep genes active or inactive.
c. They regulate translation of Hox gene mRNAs.
d. They regulate ribonucleases that control the half-life of Hox mRNA.