Operon

An operon is a set of genes that are transcribed together into a single mRNA molecule. Operons are found commonly in bacteria, but not in eukaryotes, which must regulate their genes individually. Here, we see a DNA molecule containing three genes that are transcribed simultaneously into a single polycistronic mRNA molecule, shown as a blue strand. Ribosomes bind to the mRNA and translate its sequence into three separate proteins: A, B, and C. Note that translation is continuous – when a ribosome completes the synthesis of one protein it subsequently begins to produce the next one. Operons are one method organisms can use to regulate the production of several proteins simultaneously, such that the desired concentration of each is maintained in the cell.

Question 1: What is an operon?
  1. A set of three nucleotides coding for a single amino acid.
  2. A set of three codons coding for a peptide.
  3. A set of three genes that code for a protein.
  4. A set of genes that are transcribed together into a single mRNA molecule.


Answer 1 Answer – (d) A set of genes that are transcribed together into a single mRNA molecule.

Question 2: Why are operons are not common in Eukaryotes but are common in Bacteria?
  1. Because Bacteria have fewer genes.
  2. Because Eukaryotic genes mostly have to be regulated individually.
  3. Because Eukaryotes don’t make mRNA – they only make dRNA.
  4. Because Bacteria are smaller and have to grow faster.


Answer 2 Answer – (b) Because Eukaryotic genes mostly have to be regulated individually.

Question 3: Why do organisms use operons?
  1. To regulate the production of several proteins simultaneously.
  2. To shorten the mRNA molecule.
  3. To better control individual protein production.
  4. To make cells grow larger.


Answer 3 Answer – (a) To regulate the production of several proteins simultaneously.