(A) The cyd-1 gene. Boxes, exons; lines, introns; red, cyclin box. q626 is a G to A base change that generates a missense mutation predicted to change an alanine to threonine. he116 and he112 are both predicted cyd-1 null mutations (Boxem and van den Heuvel, 2001). (B) Alignment of C. elegans (top), C. briggsae (middle), and human cyclin D1 (bottom) amino acid sequences (black boxes, identical residues; gray boxes, similar residues). The q626 mutation (blue box) is in a conserved region that lies to the C-terminal side of the cyclin box (red outline). (C) Gonad defects typical of cyd-1(q626) are more severe when placed over cyd-1(0) and are observed after depletion of cyd-1 by RNAi. (D) Comparison of cell divisions in wild-type (WT, black) and cyd-1(q626) mutants raised at restrictive temperature (red). L1, first larval stage; L2, second larval stage. Time scale in hours at 25°C. SGP divisions are delayed in cyd-1(q626) mutants relative to wild-type, but other blast cell divisions are normal.