Are physical characteristics of genitals inherited from both parents?

For a female, this would seem to make sense–a girl receives one x chromosome from each parent, so both would factor not only into determining her sex, but her physical characteristics as well, since the contribution from each parent is equal.

For a male, this seems not as simple. A boy gets his X from his mother, and the Y from his father, so his sex is determined solely by his father. (I’m ignoring XXY and other oddities.) But are the physical characteristics of the penis, scrotum, etc. also determined by the genetic information from both parents?

My initial guess would be yes, since the proto-genitals for both sexes appear similar initially, then differentiate at some point in embryonic development. Those proto-genitals would seem to be determined by both parents.

This all came about because I realized that, if a male’s genital characteristics were inherited from both parents, I could make the extremely off-color joke that my son “has his mother’s penis.” Yes, beware of me at social functions.

Wouldn’t that be, has his mother’s father’s?

Aren’t the genetic contributions from both parents to a female functionally equivalent?

You should realize that not every part of ‘maleness’ comes from the presence or action of the Y chromosome, and similarly not all of one’s physical femininity stems from the duplicity of the X chromosome, or absence of the Y. In fact, though many secondary sex characteristics do derive their origin in the presence of genes on these two chromosomes, far more are influenced or controlled by a variety of poorly-understood mechanisms, including the effect of hormonal control over the developmental characteristics of humans.

It makes a nice quip though, that bit about your mother’s penis, but it’s far from accurate. Perhaps someone with a deeper knowledge of human development can chime in.

As far as I know, there are no genes on the Y chromosome that determine the size, shape, or other attributes of the genitalia, be them male or female.

The Y chromosome does have genes for maleness, and sperm characteristics, as I recall.

A search on genes of the Y chromosome will show you that there isn’t really much else there.

No, some arespecific to the gender of the parent. For example, the genetic component of a female’s social skills comes from her father; this is known because if a woman is born with only one X chromosome, her level of social skills will depend on which parent she inherited it from. Different parts of the body are much more heavily influenced by one or the other parent.

I would like it if someone could explain this a bit further, because it seems counterintuitive to me.

I cannot speak to that study specifically, but there is a phenomenon called maternal or paternal imprinting. Genes receive modifications to their chemical structure as part of the packaging they go through in either egg or sperm development. That modification can differ maternally vs paternally. This phenomenon is observed in many genes, not just gender specific ones. The differences in modification often do not have an effect, but sometimes can. So, depending on which parent donated the particular gene, you can have a difference in gene expression, even if the genes are otherwise identical. One name for this type of general phenomenon is epigenetics.

A great example:

If the mutant gene copy came from dad and mom donates the normal copy it’s Prader Willi syndrome. The reverse and it’s Anglemen’s Syndrome.