The authors next asked if they could identify a specific sequence within the BCL$11$A enhancer that is required for BCL$11$A expression. They transfected the cells with many different guide RNAs that targeted multiple sequences all along the enhancer and analyzed the amount of fetal hemoglobin that was produced. Based on these results, they identified three potential sequences that are critical for enhancer function: $"+55","+58",$ and $"+62".$ These numbers describe the location of the sequence relative to the TSS$.$

For each of these three sequences, the authors transfected cells again with a single guide RNA that targets those specific sequences. They measured BCL$11$A expression levels and the amount of various types of globins that were produced. Below are their results.

$14.$ Introducing a single guide RNA will most likely cause what type of mutation? Which DNA repair mechanisms would have been used to create that type of mutation?

$15.$ In panel C$,$ what effect do the $+55,+58,$ and $+62$ deletions have on BCL$11$A expression compared to the control and the complete enhancer deletion?

$16.$ In panel D$,$ what effect do the $+55,+58,$ and $+62$ deletions have on beta and gamma globin production compared to the control and the complete enhancer deletion?

$17.$ Based on these results, which specific enhancer sequence has the strongest effect on globin production?

$18.$ Why is it important that the authors were able to affect globin production using a single guide RNA? You might need to continue to the next section before answering this question.