what is a  locus
Locus (genetics) A locus (plural loci) in genetics is the position on a chromosome. Each chromosome carries many genes; humans' estimated 'haploid' protein coding genes are 19,000-20,000, on the 23 different chromosomes. A variant of the similar DNA sequence located at a given locus is called an allele.
The word 'control' becomes even more interesting when we have the word locus, before it. You see, locus is defined as a position, point or place, or more specifically, a location where something occurs. A person's locus of control may be internal or external.