1: Creates nucleotide sequences, written about time after time (9)
5: Regretted backing up grasping tip of massive object (5)
7: Apprentice relinquishes heart to temptress (7)
9: Things get loose when there's a deficiency in the directions. (7)
11: Lankiest teen group lean with little energy (9)
13: Dispatch Socialist in contempt (5)
14: Arranged date in Cairo means extermination (11)
16: Frost to cover the cake (3)
17: Man, what an avant-garde US artist! (3)
18: Carelessly let teeth rot completely (2,3,6)
19: Rapidity with which heat's dissipated (5)
20: Face facts, Sir? .... Act! Lie! Lead Astray! (9)
23: Brigands put it in 16-across (7)
25: King Lear's daughter bathed in oranges and spice (7)
26: A fellow's legs may be protected by these (5)
27: Spasm set in after mothers had a little something to chew (9)