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 directly connects to the theme of researching genetic material to understand the factors that contribute to longevity, which aligns with the overall focus of the paragraph on the efforts of researchers to analyze Lonesome George's genome and compare it with other long-living species. The information provided highlights the research's purpose and its implications regarding longevity, reinforcing the idea presented in paragraph 2.