Who Determines a Son’s Penis Size — Mom’s or Dad’s Genes? Doctor: The Answer May Surprise You

Many men care about size. Urologist Dr. Huang Guan-jun says the question of whether a son’s penis size is influenced more by the father’s genes or the mother’s genes may surprise you. In reality, many factors affect penile development, but purely from a genetic perspective, “the mother’s influence may be greater than the father’s.”

Dr. Huang explained the genetics in a Facebook post:

Father’s Y chromosome = the on-switch

A son’s sex chromosomes are XY. The Y chromosome does come from the father. However, the SRY gene on the Y chromosome mainly acts as an “on-switch” in early embryonic development — its job is simply to start the formation of the testes and reproductive organs.

Mother’s X chromosome = the key engine

The real key that determines whether the tissue is sensitive to male hormones and can develop properly is the AR gene (androgen receptor gene). This gene is located on the X chromosome — which a son inherits 100% from his mother.

Dr. Huang offered a simple analogy: the male hormones provided by the father are like the “fuel for a rocket.” But the X chromosome given by the mother is what determines “how efficient the engine is and whether it can fully use that fuel.”

So, Dr. Huang joked, if your son is well-endowed, fathers shouldn’t rush to take all the credit. Remember to turn around and thank your wife for those excellent genes.