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?

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.