Can Cre be heterozygous?

If the experimental animals are Gene XCre/+;Gene YΔ/lox, then animals of Gene XCre/+;Gene YΔ/+ genotype are suitable controls. In this case, all animals are heterozygous for Gene X and recombination occurs only where Cre is expressed.

Are Cre mice homozygous?

And, Cre may also be either constitutively expressed, or inducible (this is explained more in Part 1 of this series). In any case, Cre is a dominant phenotype, while you’ll want the floxed gene to be homozygous in order for Cre-mediated recombination to affect every copy of your target gene in your experimental mice.

How are Cre mice generated?

Cre-loxP system is a widely used powerful technology for mammalian gene editing. Conditional knockout mice are then generated by breeding the Cre-driver strain with a floxed mouse strain (Figure 1B). The specificity and timing of recombination are controlled by used promoter and/or enhancer.

How many Cre Lox offspring are heterozygous?

Approximately 50% of the offspring will be heterozygous for the loxP allele and hemizygous/heterozygous for the cre transgene. Mate these mice back to the homozygous loxP -flanked mice (see Figure 2 below).

How to generate mice that are heterozygous for a loxP-flanked allele?

To generate mice that are heterozygous for a loxP -flanked allele and hemizygous/heterozygous for the cre transgene, mate a homozygous loxP -flanked mouse of interest to a cre transgenic mouse strain (see Figure 1 below). Approximately 50% of the offspring will be heterozygous for the loxP allele and hemizygous/heterozygous for the cre transgene.

Do you need homozygous CRE transgene for Cre Lox?

“Cre mosaicism” is documented in some strains, resulting in incomplete recombination in all cells. Data from the JAX Cre Resource have documented this in several examples. 8. You should not need a homozygous Cre transgene for efficient recombination Expression levels from a hemizygous transgene should be enough to see recombination.

How can I breed loxP and Cre mice?

2) Cross the heterozygous loxP, hemizygous cre mice back to the homozygous loxP, which will generate some homozygous loxP, hemizygous cre and some homozygous loxP, noncarrier mice (~25% of each), which are the genotypes needed for the end cross! See our previous blog post on Cre/lox Breeding for Dummies, which illustrates the same cross.