lizzymodblog:

stedilnik:

lizzymodblog:

stedilnik:

Identical twins

NO, THAT AIN’T RIGHT

TWINS CAN’T BE OF A DIFFERENT GENDER AND STILL BE IDENTICAL

THAT’S NOT HOW EGG CELLS WORK

“Identical twins are almost always the same sex, but surprisingly there are a tiny number of boy-girl monozygotic twins. They result from an egg that contains an unusual mixture of sex chromosomes, not the usual XX for a girl, and XY for a boy. Occasionally an egg contains three sex chromes, two X’s and a Y. But if the egg divides to produce monozygotic twins, a chromosome may be lost in the process, leaving one embryo with a girl’s XX combination, and her monozygotic twin as an XY boy.”

Such outliers are a flimsy excuse and you know it.

identical twin
noun
one of a pair of twins who develop from a single fertilized ovum and therefore have the same genotype, are of the same sex, and usually resemble each other closely.