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 furthers the discussion about how the researchers are using genetic material to understand the factors associated with longevity, aligning with the theme of studying Lonesome George's genes for insights into long life.