Medical Genetics The Steps 1. A portion of the double helix is unwound by a helicase 2. A molecule of a DNA polymerase binds to one strand of the dna and begins moving along it in the 3 to 5 direction using it as a template for assembling o leading strand of nucleotides and reforming a double helix. In eukaryotes this molecule is called DNa polymerase delta(o)Medical Genetics The Steps: 1. A portion of the double helix is unwound by a helicase. 2. A molecule of a DNA polymerase binds to one strand of the DNA and begins moving along it in the 3' to 5' direction, using it as a template for assembling a leading strand of nucleotides and reforming a double helix. In eukaryotes, this molecule is called DNA polymerase delta (δ)