Patterning in Drosophila (IMAGE) California Institute of Technology Caption A) This cross-section of an early Drosophila embryo shows the levels of the transcription factor Dorsal, which is present in a nuclear gradient. B) The predominant view in the field had been that different levels of Dorsal support the expression of distinct target genes along the dorsal-ventral axis of embryos. C) The Caltech team found that levels of nuclear Dorsal cannot account for the fact that the gene ind ceases to be expressed in dorsal regions of the embryo. Credit PNAS/Stathopoulos et al, Caltech Usage Restrictions With credit as given above License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.