[ExpertScie]

Dear Morten Jarlak,
Here is the detail of Cis-gene:-
First of all let us learn what is Cis. Cis is a Latin word. The meaning of this word will help you to understand the concept of cis-gene. It is very simple. Cis means on the "same side" of. Therefore, Cis-gene is gene (part of DNA or RNA) which regulate (means control) the expression (means function) of genes which are on same DNA (on which cis gene itself is located) and cannot control genes expresion of genes which are on another DNA (which is another concept known as trans gene regulation).
It controls functions of genes of same DNA on which it is located. The best example of this type of gene is lac Operon.
To understand cis gene and before going ahead let us first learn what is operon (best example of cis-gene) ? An operon is a functioning unit of genomic DNA. This contains a cluster of genes which have a single point control.That single point control is called as regulatory signal or promoter. Lac Operon is the best example of Cis-gene. Lac operon is operon (defined above) that is required for transport and metabolism of lactose in bacteria E. coli. This cis genes encode enzymes namely β-galactosidase, lactose permease, and thiogalactoside transacetylase.
These genes are adjacent to each other (hint : means on same part of its own DNA -Cis gene) and has single point control (so called as operon) These are called as lacZ , lac Y and lac A respectively & together constitutes lac operon (Cis-gene).