Question

To detect whether or not a cell has a specific region of a gene, researchers add radioactively labeled dna molecules that can bind to their complementary dna sequences. to detect a mutant version of the blm gene, researchers added the radioactive dna molecule 5' - gctagctaagccca - 3' to cells. what dna sequence were the researchers trying to detect?

Answer 1

I believe the answer is 3' - CGATCGATTCGGGT - 5'. This is the complementary sequence of the probe with the 3' and 5' ends lined up correctly. BLM gene is used to provide instructions for making a protein family member called RecQ Helicases. This gene is known for having mutations on both BML gene copies. 

Answer 2

The right answer is the complementary DNA sequence of the radioactive DNA molecule (the radioactive molecule is called probe).

Here is the probe: 5' - gctagctaagccca - 3'

The sequence is   3' - cgatcgattcgggt - 5'

DNA probes are segments of DNA that are labeled (radioactive label in this case) to indicate the detection of homologous segments of DNA in tissue or culture samples.