Question

1. what is the key to the linking of nucleotides that form the sugar - phosphate backbone of dna?

a phosphoester bond
a polar bond
a weak hydrogen bond

Explanation:

Nucleotides in nucleic - acids are linked by phosphodiester bonds. A phosphodiester bond forms between the 3'-hydroxyl group of one nucleotide and the 5'-phosphate group of another nucleotide, creating the sugar - phosphate backbone of DNA and RNA. Polar bonds and weak hydrogen bonds are not the key for this linkage.

Answer:

a phosphodiester bond