The sentence that best helps develop the idea expressed in paragraph 2 is: "Thanks to this analysis, the researchers were able to narrow down their original list of 3,000 genes to 43 specific sequences that might have contributed to Lonesome George’s long, disease-free life."
This sentence provides specific information on the outcomes of targeting the genes, showing how the research led to a focused understanding of the genetic factors involved in Lonesome George’s longevity.