As is the case with most evolution-inspired ideas, the more we learn about the natural world, the more it becomes obvious that there is very little “junk DNA” in nature. A recently-published study of gender in mice highlights this fact. In the study, an international collaboration of scientists examined the development of sexual characteristics in mice. As you probably already know, in mammals there is a pair of chromosomes referred to as sex chromosomes. If an individual has an X chromosome and a Y chromosome in that pair, he is a male. If the individual has two X chromosomes, she is a female.
But the development of the proper characteristics associated with each sex depends on what happens during embryonic development. For example, as a mammal embryo develops, it starts out producing ovaries. However, there is a gene on the Y chromosome called Sry. It produces a protein that controls the production of another protein, called SOX9. The SOX9 protein turns developing ovaries into testes. A male develops testes, then, because of the action of a gene on the Y chromosome. But as this latest study shows, there is more to it than that.
The scientists removed a small section of DNA from genetically-male mice. This section is found in what the authors refer to as a “gene desert,” a section of DNA that is devoid of genes. Nevertheless, when that small section of DNA was deleted, the genetically-male mice developed ovaries and female genitalia. Now please understand that the genes involved in the production and regulation of the SOX9 protein were not removed; only a small portion of what many would call “junk DNA” was removed. Nevertheless, without that section of DNA, the genetically-male mice did not produce enough SOX9 protein, so the ovaries continued to develop into ovaries, which then caused the production of female genitalia. As a result, the authors refer to this small section of DNA as a SOX9 “enhancer.” It enhances the production of SOX9 at just the right time, so the males develop the correct gender characteristics.
While the results of this study are fascinating, they are not surprising. After all, it has become more and more clear that the concept of “junk DNA” is a myth. As a result, it makes sense that even small sections of DNA have important functions, at least in certain stages of development or under certain conditions. The reason I am blogging about the study is because of something the lead author said in an article that was published on his institution’s website:
Our study also highlights the important role of what some still refer to as ‘junk’ DNA, which makes up 98% of our genome. If a single enhancer can have this impact on sex determination, other non-coding regions might have similarly drastic effects. For decades, researchers have looked for genes that cause disorders of sex development but we haven’t been able to find the genetic cause for over half of them. Our latest study suggests that many answers could lie in the non-coding regions, which we will now investigate further.
Indeed. As Dr. John Mattick so aptly put it more than a decade ago:
…the failure to recognise the implications of the non-coding DNA will go down as the biggest mistake in the history of molecular biology.
Awesome article! Really does illustrate how ridiculous it is for genetic scientists to make broad sweeping statements about a science they know so little about.
Awesome post Dr. Wile! I can’t believe people still believe in evolution when the facts say otherwise!
In other words, it is just now, in 2018, that we will be looking for the genetic causes of sex disorders in non-coding regions. Why? Because Darwinian theory predicted that these non-coding regions were “junk DNA,” and so scientists considered it meaningless to study them. I find this particularly striking, since it is not only a falsification of Darwinian predictions, but it is an example of Darwinian assumptions hurting scientific progress! Imagine, how many disorders might have been understood – even cured – by now had it not been for Darwin and the assumption of “junk DNA?” In the end, the assumption of large portions of “junk DNA” – which Darwinian theory requires – has not only been mostly falsified, but it actually has been holding science back for over 100 years.
Back with a small question. A while back, I read an article about sexual development in the embryonic stages. In it, it stated that everyone begins as a female. Is there any truth behind that? It seems like the experiment could suggest that. Because the SOX9 protein wasn’t present, then development would continue into a female with FOXL2. A lot of this is Greek to me. I was home-schooled, and because of that, my knowledge of science isn’t the best. It was something that didn’t play a big role in my curriculum. With that being said, I know its never too late to learn. I just don’t know where to start
It’s not true that everyone begins as a female, but I can see where that notion comes from. The genome of a person is determined at conception. When the father’s sperm unites with the mother’s egg, a new genome is formed. At that point, the person is either male (with one X and one Y chromosome as the 23rd pair) or female (with two X chromosomes as the 23rd pair). Now, during embryonic development, a structure is formed that will, eventually, become the gonad for sexual reproduction. Without the proper amount of SOX9 protein at the proper time, that structure will develop into an ovary. With the proper amount of SOX9 protein at the proper time, it will develop into a testis. The gonad then produces other physical characteristics of each sex.
The reason it’s improper to say that everyone starts out female is because the initial structure is neither an ovary nor a testis. It is a group of tissues that will become either an ovary or a testis. Even if there is a genetic problem (such as Swyer syndrome) and the structure eventually becomes an ovary in an XY individual, that person is still not a female. The person’s ovaries are not functional, and often become cancerous. Also, there is a hormone imbalance, so without hormone therapy, the uterus cannot grow and the breasts do not develop properly. So, with intervention, a male with a genetic abnormality can be made to look more female. However, he will not actually be female. The person is often referred to as an “XY female.”
I think Wikipedia(though isn’t the better source of information for everything) is correct to say: “Fetuses before sexual differentiation are sometimes described as female by doctors explaining the process. This is technically not true. Before this stage, humans are simply undifferentiated and possess a Müllerian duct, a Wolffian duct, and a genital tubercle.” See here.
Humans aren’t “completely females” at uterus. Males humans possess complex interplay between genes and hormones. For more details, click<a href="https://en.wikipedia.org/wiki/Sexual_differentiation" here.