Question

To generate a knockin mouse, a scientist introduces to ES cells a construct with a mutant exon and within an adjacent intron, loxP sites flanking a neomycin resistance gene. What event will occur next?a. Crossing of heterozygous mice to a Cre-expressing strain.b. Homologous recombination between the mutant DNA and the corresponding gene in the mouse genome.c. Recombination between the loxP sites.d. Transplantation of cells into host blastocyst.

Answer 1

Answer:

b. Homologous recombination between the mutant DNA and the corresponding gene in the mouse genome

Explanation:

The Cre-lox recombination system is a versatile mammalian gene-editing tool used to produce site-specific recombination events in specific cell lines (e.g., embryonic stem or 'ES' cell lines) by facilitating the integration of a circular mol­ecule in genomic DNA. This system makes use of a Cre recombinase enzyme from bacteriophage P1 that has the ability to recombine specific sequences referred to as Lox sequences. By using this system, it is possible to generate knockout mice by crossing a strain of mice expressing Cre recombinase strain with a targeted loxP-flanked (floxed) mouse strain. The generation of a floxed mouse consists of 1-generation of a targeting construct containing homologous sequences with the mouse genome and loxP sites flanking the gene sequence of interest, and 2-homologous recombination of the targeting construct with the endogenous target gene sequence in the mouse genome.