Abstract: The present invention relates to polypeptides, compositions and methods for enhancing synthesis of nucleic acid molecules. In a preferred aspect, the invention relates to inhibition or control of nucleic acid synthesis, sequencing or amplification. Specifically, the present invention discloses polypeptides having affinity for double-stranded and/or single-stranded nucleic acid molecules and/or single-stranded/double-stranded nucleic acid complexes (e.g., primer/template complexes, double-stranded templates, single-stranded templates or single-stranded primers) for use in such enhanced synthesis and more particularly to polymerases having reduced polymerase and optionally reduced exonuclease activities (3? to 5? and/or 5? to 3? exonuclease activity), and to nucleases having reduced nuclease activity. The polypeptides of the invention are capable of inhibiting nonspecific nucleic acid synthesis at ambient temperature.