There is no need to change DNA.  There is woman in man, and there is man in woman.  All human beings are body-persons, homogeneous in the whole being (see the Theology of the Body, 8:4).  

https://www.ewtn.com/library/PAPALDOC/jp2tb8.htm

Actually, at conception, we all start like girls.  Sexual differentiation happens *after* conception, but all men and women share one and the same human nature, same flesh.