Gender and Sex – Part 1 – Conception to Birth

In recent months there has been a flurry of media attention and both pro and con arguments surrounding such topics as “gender identity,” “bathroom bills,” etc. There is also a lot of misinformation or partial information in many of the articles I have read. Depending on your own personal background you may have preconceived ideas about these topics – I know I did. So I decided to do some of my own research and see what I could find and put together this blog entry in a way that I hope can help others understand all these topics.

There are multiple aspects to the term “gender” and that is part of what makes this so complicated. I’m going to individually try to put some sense/definition to five aspects, then tie them all together. I will address these aspects in an order that moves from the more “scientific” or fact based to the more “feeling” based – and thus in increasing order of controversy.

The Genetic Aspect

At the lowest level we are defined as male/female by our genes. While we have all probably had some discussion about those with XX chromosomes being female and those with XY chromosomes being male, it’s far more complicated than that. Here is a quite technical definition of this topic that is quite informative - https://en.wikipedia.org/wiki/Aneuploidy. But I’m going to summarize it here so you don’t have to read the gritty details.

The cells in the human body have (usually) 23 pairs of chromosomes. One copy of each pair is inherited from the mother and one from the father. The pairs are numbered 1-22 and the 23^rd “pair” are the XX/XY pair. The mother always contributes an X to the 23^rd pair and the father contributes either an X or a Y. This is what you’ve always been taught in elementary biology. However, things are not that simple. There are two not uncommon complicating factors.

First, sometimes there is not a simple “pair”. There can be a single copy instead of two; there can be more than two in the set. These are called “monosomy” and “trisomy”, “tetrasomy” or “pentasomy” (3, 4, 5). Most of the variations, especially the trisomy and higher types, are fatal, i.e. if they occur in an individual there will be a miscarriage. Many of the “monosomy” ones are not fatal, but there are often development issues in individuals which have them. The most common of these variations is “trisomy 21”, i.e. having three copies of the 21^st chromosome. You may know this as “Down Syndrome”. This is never (as long as there are no other complicating factors) fatal.

There are also possible variations in the 23^rd chromosome, i.e. the sex determining chromosomes. The above Wikipedia page has a chart of all the variations. From this we can see (1) that any combinations that have only Y instances (i.e. Y, YY, YYY, etc.) are fatal. The Y chromosome is physically shorter than the X chromosome and there are necessary genes for human existence on the X chromosome. Also (2) any combination, no matter how complicated, that has at least one Y chromosome will cause the individual to be a male. Only those with only X chromosomes (i.e. X, XX, XXX, etc.) are classified as a female.

In particular, both XX and XXX result in a normal female; both XY and XYY result in a normal male (and the genetic variation can only be determined through gene analysis as the individual is not aware of any variation); and the other combinations result in a “abnormal” male or female depending on whether the combination contains a Y or not. However, many of these “abnormal” individuals only tend to have things like excessive height (XXY) or other non-fatal characteristics. But there is no connection between these genetic variations and the other gender topics I will discuss below.

Secondly, however, there are also instances where the individual is “mosaicked”, i.e. some of the cells in the body have one genetic makeup and others have a different genetic makeup. These types of situations, like the first ones I just discussed, are caused by things like incomplete/unusual cell splitting, cell recombining (e.g. there being two fertilized eggs from different sperm cells that bond together), and other similar circumstances. If this matrixed form occurs in the sex chromosomes, there may be some biological impact (see the next topic).

Summary – except for certain mosaicism variations, all individuals are classified as either genetically male or genetically female. Even those which are classified as “abnormal” males or females are fully human, just as an individual with Down Syndrome is fully human.

The Biological Aspect

Between the fertilization of an egg and the birth of the resultant individual there are typically 40 weeks of development. During this time there is much that happens – cells divide, they begin to specialize, turning into the various organs and other parts of the body, some organs produce hormones, etc. All this is done in the environment of the mother’s womb where nutrition is provided through the placenta, etc.

When the baby is finally delivered, there is a medical determination of the biological sex of the individual. This determination is based on five factors:

·         Number and type of sex chromosomes

·         Types of gonads – ovaries or testicles

·         Sex hormones

·         Internal reproductive anatomy (such as the uterus in females)

·         External genitalia

For most people these factors are either all male or all female. However there are a small number (estimates range from .018% to 1.7% depending on what variations are included) where not all these factors are in agreement. These individuals are medically assigned as “intersex” (see https://en.wikipedia.org/wiki/Intersex). There are a variety of causes for this. Besides the mosaicism mentioned above, sometimes the various internal glands in the developing individual do not produce enough of certain hormones (or may produce too much) and this causes other organs to be undeveloped or otherwise modified. You can read the article if you want more detail.

Note – not included in the above analysis is a condition known as “Cryptorchidism” where the male testes are absent/undescended from the scrotum at birth (see https://en.wikipedia.org/wiki/Cryptorchidism). This occurs in 3% of full-term male infants and 30% of premature male infants, but by age 1 in less than 1% of all males. This is classified as a development issue, not as an intersex issue.

In the past, babies who were born with ambiguous genitalia were often subject to immediate surgical procedures to make them more obviously male/female. However, this is less common today.

Summary – there are a small number of individuals whose biological sex (or at least some aspect of it) is not consistent with their genetic sex. Some of these may not be apparent at birth and the individual may not know it unless they receive genetic testing because it does not manifest in their phenotype. 


Continue to part 2 - https://ramblinrussells.blogspot.com/2016/05/gender-and-sex-part-2-adult.html