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 about the researchers' efforts to understand the genetic factors contributing to longevity, thereby supporting the discussion of the genetic analysis in the context of studying aging and health.