2. Gene = DNA sequence on chromosome. Read in 5' to 3' direction. Promoter is upstream of start codon (5' end; not translated). Terminator is downstream of stop codon (3' end; not translated).
3. Gene expression tightly regulated. Some genes expressed only once during development; others expressed continuously (housekeeping genes); some switched on and off on a regular basis.
4. Prokaryotes control gene expression at transcriptional level; activator protein; repressor protein; operon.
5. Eukaryotes more complex because of compartments formed by membrane-bound organelles and differentiation; signaling (hormones); transcriptional, transport, translational, post-translational controls; totipotency.