Why was using reverse transcriptase necessary for finding a way to make artificial insulin?

a. scientists had to convert information from amino acids to nucleic acids.

b. insulin is made of a chain of nucleic acids.
c. scientists already knew the base sequence for the insulin gene.
d. dna polymerase is the molecule that builds insulin.

A.Scientists had to convert information from amino acids to nucleic acids.

Explanation:

Reverse transcriptase is the enzyme that can form the DNA copies of RNA template. The DNA formed by using RNA as template is called as cDNA. Since the amino acid sequence of insulin was known, the respective mRNA was synthesized using genetic codes. The mRNA was copied into its cDNA copy using reverse transcriptase enzyme. This was followed in insertion of insulin gene into the plasmid vector. hence,  using reverse transcriptase necessary for production of insulin gene from its known amino acid sequence.

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i think its the first one