The word endonuclease is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 20
Highest Scoring Words With Friends™ Play In The Letters endonuclease
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Seven Letter Word Alert: (37 words)
acnodes, candles, cleaned, cleanse, coulees, counsel, deacons, decanes, decease, decenes, delouse, descale, elodeas, encased, enclose, encodes, enolase, euclase, needles, nodules, nonlead, nonsale, nuanced, nuances, nucleon, scalene, scanned, seclude, solaced, uncased, unclads, unclean, unclose, unlaced, unlaces, unladen, unloads