Practice question

The Cre-loxP recombination system is derived from bacteriophage P1, a temperate phage infecting Escherichia coli. P1 uses this site-specific recombination to circularize its linear genome after infection and to ensure proper plasmid prophage segregation. Cre recombinase gene lies within P1 genome, while loxP sites represent its cognate target. Early molecular work isolated Cre activity without host factors, allowing transfer to eukaryotes. Its independence from bacterial cofactors enabled adaptation for chromosome engineering in yeast, plants, and transgenic mice for conditional knockouts.