Hello Thắng Nguyễn Phước Quý

This technique is usually done to test predictions made about the order in which genes function. Organisms can be made that are mutant in two different genes. If these mutations affect two different steps in the same process, then such double mutants should have a phenotype identical to that of the mutation that acts earliest in the pathway.

Let me explain to you in a better way with an example.

Let us consider the pathway of protein secretion say, in yeast. Different mutations in this pathway cause proteins to accumulate aberrantly in the endoplasmic reticulum (ER) or in the Golgi apparatus. When a cell is engineered to harbor both a mutation that blocks protein processing in the ER and a mutation that blocks processing in the Golgi compartment, proteins will accumulate in the ER. This will indicate to us that proteins must pass through the ER before being sent to the Golgi, before secretion.

So, using this technique (genetics) we can determine the order of function of genes.

I hope this explanation will help you!

Best.

Thank you for your helpful explaination. Could you please help me with one more question? How do I understand this symbol "aerA/(delta)aerB"? It means that gene aerA is wildtype phenotype and aerB gene is mutant, doesn't it?

Thắng Nguyễn Phước Quý, in genetics, when Greek letter "delta" is used it usually stands for deletion. So, I feel you are right.

I am genuinely thankful for your assistance.