Hi Carter,
We typically use ubiquitous Gal4 drivers, including da (daughterless)-Gal4, Actin-Gal4, and Tubulin-Gal4.
Tub-Gal4 and Act-Gal4 lead to very high levels of expression. In contrast, da-Gal4-mediated expression results in lower levels of expression than those from Tub- or Act-Gal4. Therefore, if your gene of interest has gain-of-function effects (phenotypes caused by overexpression of your wild-type gene), a weaker driver is a better choice.
I tested 3-4 different Gal4, including strong and weak drivers, to determine which drivers show the optimal rescue for loss-of-function mutants.
Double balancer flies can combine Gal4 or UAS-gene with your mutant alleles if located in different chromosomes.
If the mutant allele and UAS transgene or Gal4 drivers are located on the same chromosome, you need to recombine your UAS transgenes or Gal4 drivers with your mutant allele.
In addition, T2A-Gal4 mutants(Lee et al. eLife 2018; Diao et al. Cell rep. 2015; Yoon et al. 2017 Neuron) have worked well to rescue their loss by combining UAS-wildtype target genes.
Please let me know if you have more questions.
Best wishes,
Wan Hee