Practice question

Placing loxP sites in same orientation flanking exon 2 and intronic regions preserves gene function until Cre acts. Cre recombinase synapses two directly repeated loxP sites, forming a loop and catalyzing strand exchange. Recombination excises the looped DNA as circular molecule containing exon 2 and one loxP site, leaving single loxP scar in chromosome. Loss of coding exon causes frameshift mediated nonsense or deletion of essential domain, achieving conditional knockout after tissue specific Cre activation without affecting other tissues developmentally.