frameshift mutation / frame-shift mutation; frameshift. A frameshift mutation is a genetic mutation caused by a deletion or insertion in a DNA sequence that shifts the way the sequence is read. A DNA sequence is a chain of many smaller molecules called nucleotides.
As for Flexeril (cyclobenzaprine) is is not a controlled substance under US, Canadian, or international law. Some drugs used as muscle relaxants ARE controlled substances like Valium and many US states and countries have listed Soma (carisoprodol) as a controlled substance (or prohibited it).
What is a controlled medicine (drug)? Some prescription medicines are controlled under the Misuse of Drugs legislation (and subsequent amendments). These medicines are called controlled medicines or controlled drugs. The Misuse of Drugs Regulations 2001 has a full list of controlled medicines. Legal controls.