Try it on paper first. A hint, the key idea and the worked solution are here when you need them.
A student writes the steps of recombinant DNA technology in a mixed order.
A. Grow the cells in a bioreactor.
B. Cut the DNA with a restriction enzyme.
C. Select the recombinant cells.
D. Isolate the DNA from the cells.
E. Put the recombinant DNA into a host.
F. Ligate the gene into the vector.
G. Separate and purify the product.
Downstream processing is separation, purification, formulation with preservatives and quality control. A drug also goes through clinical trials. The overall yield is the product of the yields of the steps.
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. Seven steps.
Plan. Follow the path of the DNA, and then the path of the product.
Step 1. (a) The order is D, B, F, E, C, A, G. First isolate the DNA (D) and cut it (B). Then ligate the gene into the vector (F) and put it into a host (E). Select the recombinants (C), and grow the cells in a bioreactor (A). Last, separate and purify the product (G).
Step 2. (b) Downstream processing starts after the culture, with the separation of the product.
Answer: (a) D, B, F, E, C, A, G. (b) Separation of the product.
Check. The cells are selected before they are grown in a large tank, so C comes before A.
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