ZYGOSIS

- The union of gametes to form a zygote; conjugation.

Z10 - Y4 - G2 - O1 - S1 - I1 - S1 has 20 points in Scrabble!

Z10 - Y3 - G3 - O1 - S1 - I1 - S1 has 20 points in Words with Friends!

Found in the OTCWL2014, SOWPODS, ENABLE, and WWF dictionaries