A 10 kb linear DNA is cut with EcoRI and HindIII.The EcoRI digest yields fragments of 2 and 8 kb.The HindIII digest yields fragments of 3 and 7 kb.What are the possible fragments (in kb)from an EcoRI-HindIII double digest?

Question

Quizplus · Accepted Answer

The EcoRI digest produces fragments of 2 and 8 kb, which means that the recognition site of EcoRI is located in the middle of the original 10 kb DNA. Therefore, the EcoRI digest splits the original DNA into two fragments of equal size.
The HindIII digest produces fragments of 3 and 7 kb, which means that the recognition site of HindIII is not located in the middle of the original 10 kb DNA.
When combining the digestions, the fragments generated will have one end that is from the EcoRI digestion and another end from the HindIII digestion. The 2 kb EcoRI fragment will pair with the 7 kb HindIII fragment to generate a fragment of size 9 kb. The 8 kb EcoRI fragment will pair with the 3 kb HindIII fragment to generate a fragment of size 11 kb. The only possible remaining fragment is 1 kb, which is generated by one of the cleavages from the HindIII digestion that does not combine with any of the EcoRI fragments. Therefore, the possible fragments from the EcoRI-HindIII double digest are 1,2,7 or 2,3,5. The correct answer is E.

A 10 Kb Linear DNA Is Cut with EcoRI and HindIII.The