Practice question

In Cre-loxP system Cre binds 13 base pair inverted repeats surrounding 8 base pair asymmetric core of loxP. For inversion versus deletion decision, relative direction of core determines outcome. When core sequences point towards each other on same chromosome, meaning loxP sites in opposite orientation, Cre catalyzed recombination reverses intervening segment without loss. Direct repeats cause deletion. Thus requirement for inversion is antiparallel loxP orientation ensuring DNA strand exchanged leads to reversal rather than circular excision, employed in FLEX switches for reversible gene control.