If you were to use crispr to cleave dna at sites flanking a gene, and in this way produce a deletion of the gene, how many sgrnas would you need?

2

Explanation:

If the sequence that you want to delete is flanked by different sequences, you will need 2 sgRNAs: one to produce the cut at the 5´ side, and other complementary at the 3´ site.

However, in the unlikely case in which both of the flanking sequences are almost the same ( more than a 90% of identity)  or if it is a palindromic pattern, you can use the same sgRNA to guide the cuts.

Hope you luck!

the real answer is b. scintillation counter