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 genetic analysis conducted by the researchers and emphasizes the connection between Lonesome George’s genetics and the study of long life, which aligns with the paragraph’s focus on using his genetic material to understand the biology of longevity.