File:Commonly used cell lineage marking strategies..jpg

English: A. Tubulin-lacZ approach. Heat shock activates expression of the Flipase (FLP) gene, driving inter-chromosomal recombination at FRT sites to re-constitute the Tubulin (Tub) promoter-LacZ reporter construct. Colored arrows indicate segregation fate of chromosomes. Cells on right are the product of a division following recombination- one of two daughter cells inherits a functional reporter (+). B. Cre-ER approach. A tissue specific promoter (**) drives expression of Cre-ER. Tamoxifen addition permits activation of Cre-ER, allowing removal of an intervening stop sequence in the Rosa-LacZ reporter construct. Left cell- G2 recombination. Middle cell- after recombination- one chromatid contains a functional reporter (+). Right cell- products of division of middle cell. C. Negatively marked clones. Heat shock FLP-mediated recombination results in the segregation, upon division (daughter cells on right) of a mutation from an Ubiquitin (Ubi)-GFP transgene, resulting in a homozygous mutant, GFP- cell. D. MARCM clones. Heat shock permits FLP-mediated FRT recombination. Arrows indicate segregation fate of chromosomes. Daughter cells shown on right: both copies of Tub-Gal80 segregate from both copies of a mutation (mut). Cells that lose Gal80 activate Gal4, which permits expression of the UAS-GFP reporter (indicated by loss of red X). Key: All recombination events represent events in G2 (left cell in each part). Orange circle- centromere, Purple circle- recombinase sites, Blue “X”- recombination, Light blue box – promoter, Red octagon–intervening stop sequence, Yellow arrow- active transcription, Yellow box- Recombinase, regulatory or mutated effector (mut) genes, White box–gene inactive, Blue box – active LacZ gene, Green box –active GFP gene.