indifferent gonad

Genes that form the sexually indifferent gonad are SF1 and WT1.

By the fifth week, the genital ridges differentiate into an outer cortex and an inner medulla, and are called indifferent gonads.

When such a gene is defective, the indifferent gonads fail to differentiate into testes in an XY (genetically male) fetus.

During these six weeks, the XY/XX embryos develop an indifferent gonad, an extra layer that isn't affected by the chromosome embryo due to their indistinguishable similarity at the time.

Genes associated with the developing gonad can be categorized into those that form the sexually indifferent gonad, those that determine whether the indifferent gonad will differentiate as male or female, and those that promote differentiation into male or female parts.