Final answer:
An exonuclease is an enzyme that removes nucleotides from the ends of DNA or RNA strands in a 3' to 5' direction. It is responsible for removing RNA primers and replacing them with DNA during DNA replication.
Step-by-step explanation:
Enzymes that eliminate nucleotides from the ends of DNA or RNA strands are known as exonucleases. It works by hydrolyzing the phosphodiester bond that connects the final nucleotide to the neighboring nucleotide in the 3' to 5' direction. Exonuclease activity plays a role in DNA replication by eliminating RNA primers and substituting them with freshly made DNA. While exonuclease activity more widely refers to enzymes that can remove nucleotides from the ends of DNA or RNA molecules, exon sequence refers to the protein-coding sequence in a gene that is eventually expressed.