The enzyme responsible for attaching free-floating nucleotides to an open strand of DNA during replication is DNA polymerase.

Here's how it works:

1. DNA polymerase binds to the template strand: DNA polymerase recognizes the template strand (the strand being copied) and binds to it.

2. Matching nucleotides are added: DNA polymerase reads the template strand and adds complementary nucleotides to the growing new strand. For example, if the template strand has a cytosine (C), DNA polymerase will add a guanine (G) to the new strand.

3. Proofreading: DNA polymerase has a built-in proofreading mechanism that checks for errors and corrects them if necessary.

There are different types of DNA polymerases in cells, each with specific roles in DNA replication. For example, DNA polymerase III is the primary enzyme responsible for synthesizing new DNA strands in bacteria, while DNA polymerase α, δ, and ε play key roles in eukaryotic DNA replication.

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