List the advantages of recombinant insulin.

(N/A) $1$. Ethical Advantage: There is no need to sacrifice animals (cattle and pigs) to extract insulin,which was the traditional method.
$2$. Reduced Immunogenicity: Insulin extracted from animals often caused allergies or immune reactions in patients due to the presence of foreign proteins. Recombinant human insulin is identical to natural human insulin,minimizing these reactions.
$3$. Purity and Availability: Recombinant $DNA$ technology allows for the mass production of pure human insulin in $E. coli$,ensuring a consistent supply and reducing the risk of contamination.
$4$. Cost-Effectiveness: While initial development was complex,the large-scale production of Humulin is efficient and cost-effective compared to the extraction process from animal pancreases.