The enzyme $DNA$ polymerase in $E. coli$ is a $DNA$-dependent polymerase and also has the ability to proof-read the $DNA$ strand being synthesized. Explain. Discuss the dual polymerase activity.

(N/A) $DNA$ polymerase in $E. coli$ exhibits dual activity:
$1$. $DNA$-dependent $DNA$ polymerase activity: It catalyzes the polymerization of deoxyribonucleotides by reading the template $DNA$ strand,ensuring the synthesis of a complementary strand in the $5' \rightarrow 3'$ direction.
$2$. Proofreading activity ($3' \rightarrow 5'$ exonuclease activity): During replication,if an incorrect nucleotide is incorporated,the enzyme recognizes the mismatch. It then uses its $3' \rightarrow 5'$ exonuclease activity to remove the incorrect nucleotide and replaces it with the correct one,thereby ensuring high fidelity of replication.