What is a woman? Or a man? It’s all in your genes

By Patricia Weerakoon 

The Bible says God created humanity male and female. But the Bible doesn’t give us detailed information about how our bodies develop as either male or female. 

God did however give us the ability to carefully analyse the world and discover the processes whereby our sex development takes place. In terms of Christian theology, this ability to understand the world fits into the broad category of what the Bible calls ‘wisdom.’ King Solomon, the figurehead of Old Testament wisdom, analysed the world: he “spoke about plant life … animals and birds, reptiles and fish” (1 Kings 4:33). 

In God’s kindness to humanity, discovering these processes does not require religious faith – Christian or any other. All it requires is the humility to pay attention to the external objective realities of the world. 

That’s what science does. ‘Religious’ people interpret those realities as being established by God. Atheists don’t. But both accept the authority of that external objective reality which they do not create but discover. Through humble engagement with that reality, they achieve wisdom which helps them navigate life in this world. And that wisdom also equips them to help others navigate life in this world. 

In an earlier blog post we explored how sex chromosomes determine your sex. 22 pairs of autosomes and XX sex chromosomes make you a female. 22 pairs of autosomes and XY sex chromosomes make you male. We also discussed the definition of male and female based on the two distinct reproductive apparatuses (internal and external genitalia) and two complementary reproductive strategies. Different gonads – testis in males and ovaries in females – produce and deliver genetic material in two types of sex cells called gametes: sperms in men and ova or eggs in females. 

But what about situations where the sex chromosomes do not match the typical definition of XY male and XX female? 

Sometimes things go wrong in the development of sperm and ova or during fertilisation and we have a zygote that is neither XX or XY. These include: 

• XO (no second sex chromosome): Turner Syndrome; 
• XXY: Klinefelter syndrome; 
• XXX: Trisomy X 
• XYY: Jacob’s syndrome. 

These atypical patterns are classified as disorders (or differences) of sex development (DSDs), commonly called intersex conditions. 

Are these chromosomal variations evidence that sex is not binary? Are they evidence that sex is a spectrum?

No, they’re not. Because there’s more to binary sex than chromosomes. It’s in your genes. 

Strictly speaking, sex chromosomes do not themselves determine your sex. The genetic information they carry does that. 

As the baby (the foetus) grows in its mother’s womb, the genes carried by the sex chromosomes trigger and control the differentiation of the baby’s body structure in either a male or female direction. They cause undifferentiated gonadal cells to develop into either ovaries or testes. They initiate and guide the development of the internal and external genitalia. 

The gene which mainly drives this binary sex differentiation is called the SRY gene. It’s carried by the Y chromosome. This SRY gene does two things. 

1. It suppresses the genes that trigger ovarian development and 
2. It enables those that direct the tissues in the developing baby in the 4-6th week (now called an embryo) to develop into testes. 

If there is no SRY gene, then the pathway of ovarian development continues unsuppressed. Ovaries develop. And without the testes and testosterone, a female body develops.

The presence of two X chromosomes does not ‘overcome’ the effect of the SRY gene. A foetus with Klinefelter syndrome has two X chromosomes and one Y. You can, extremely rarely, have three Xs and one Y, or even four Xs and one Y! But despite the extra X chromosomes, all these cases develop a testis and a male body structure thanks to the presence of SRY gene on the Y chromosome. 

It works the other way too. You don’t need two Xs for a female body structure. All you need is the absence of the SRY gene, usually through the absence of the Y chromosome. So with Turner syndrome, a foetus with only one X chromosome will still develop female genitalia and associated female body structure. 

Look again at the conditions we noted above, and the atypical chromosomal combinations associated with them. You’ll see that with all of them, the presence or absence of the Y chromosome is a binary variable. You either have that Y chromosome or you don’t. 

The presence of the SRY gene on the Y chromosome guides the foetus to develop the genital structure of a male. In the absence of the SRY gene, the foetus will develop the genital structure of a female. 

So that means that in the above four conditions:

• XO Turner Syndrome: the foetus has no SRY gene therefore will develop a female body structure; 
• XXY Klinefelter syndrome: the foetus has the SRY gene therefore will develop a male body structure; 
• Trisomy X: the foetus has no SRY gene therefore will develop a female body; 
• XYY Jacob’s syndrome: the foetus has the SRY gene therefore will develop a male body.

People with these conditions tend to be infertile and experience all kinds of associated comorbidities. 

Klinefelter syndrome commonly results in smaller than average testes, low testosterone levels, infertility, breast development, and decreased muscle mass and bone density. It is one of the most common DSDs, affecting about one in 500 to one in 1000 newborn boys. It only affects males. For more info, have a look at this video from the Paradox Institute. 

Turner syndrome affects about one in 2500 newborn girls. Females with Turner syndrome have nonfunctional ovaries and are therefore infertile. They tend to be shorter than their female counterparts who possess XX chromosomes. They may have extra folds of the skin on the neck, skeletal differences, and kidney problems. One-third to one-half of affected females are born with heart defects. For more info, see the Paradox Institute's video.  

What this tells us is that possessing atypical chromosomes is not a good thing. These conditions really are disorders of sex development. People who suffer from them deserve compassion and sympathy for the hardships associated with their condition. 

However, we can also see that God has, out of his kindness, made our bodies strong enough to survive such disorders. The presence of absence of the SRY gene enables people to adequately possess a body pattern which clearly defines their sex as male or female, even if they possess something other than the typical XX or XY gene pairing. 

People who possess atypical chromosomes can still live whole, happy lives, as either male or female. Let’s celebrate that and get on with enjoying life as the body God has given us.