How is sex determined?

Posted 16 February 2014 by M. Wilson Sayres

A fun video introducing the variety of sex determination systems:

http://youtu.be/kMWxuF9YW38 I like this as an introduction, which sets some good rules of thumb, but there are some excellent exceptions to these rules that we can get into. For example, in mammals (even humans), the part of the Y chromosome that is most responsible for turning on the male-determining pathway doesn't always function as it should, resulting in individuals with an X and a Y chromosome who have female physical characteristics (for more see Ed Yong's article about Chen et al.'s 2013 paper).

28 Comments

DS · 17 February 2014

It is interesting to speculate that, ironically, these problems might arise due to the essentially asexual nature of the Y chromosome. The situation is similar in mitochondrial DNA, except that the copy number is much different. Once again, it may impossible to understand the system except in the light of evolution. It certainly isn't very intelligently designed.

debunkingdenialism.com · 17 February 2014

For example, in mammals (even humans), the part of the Y chromosome that is most responsible for turning on the male-determining pathway doesn’t always function as it should, resulting in individuals with an X and a Y chromosome who have female physical characteristics

Most cases of androgen insensitivity syndrome is caused by a mutation in the androgen receptor. This receptor is encoded by a gene on the X chromosome, not Y (Chang et al, 1988).

these problems might arise due to the essentially asexual nature of the Y chromosome

The Y chromosome can undergo a process called gene conversion. According to Rozen et. al. (2003), the regions specific to the Y chromosome have ~99% intra-palindromic sequence identity. Thus it is not completely accurate to call it "essentially asexual". References: Chang C.S., Kokontis J., Liao S.T. (1988). Molecular cloning of human and rat complementary DNA encoding androgen receptors. Science 240(4850). 324–6. Rozen, S., Skaletsky, H., Marszalek, J. D., Minx, P. J., Cordum, H. S., Waterston, R. H., . . . Page, D. C. (2003). Abundant gene conversion between arms of palindromes in human and ape Y chromosomes. Nature, 423(6942), 873-876

Paul Burnett · 17 February 2014

Melissa wrote "for more see Ed Yong’s article about Chen et al.’s 2013 paper."

Ed Yong's article mentions "Melissa Wilson-Sayres from the University of Berkeley"!

You've moved? [grin]

fnxtr · 17 February 2014

I know someone with a form of CAIS. All woman, minus a uterus. Oh, and at 16 or so they took out testes where ovaries were supposed to be.

Just Bob · 17 February 2014

*Gasp!* You mean there are some people who aren't exactly all male or all female, but maybe in between, or both at the same time?

Another lie from the Pit of Hell! The Bible says...

Jim · 17 February 2014

My wife used to be a nurse in a urologist's office. One day a 12-year old came in complaining of bleeding from the penis. In fact, he (she) was having her first period. Explaining the situation to the parents and the child was extremely difficult and made more so by the patient's mild retardation.

M. Wilson Sayres · 17 February 2014

Paul Burnett said: Melissa wrote "for more see Ed Yong’s article about Chen et al.’s 2013 paper." Ed Yong's article mentions "Melissa Wilson-Sayres from the University of Berkeley"! You've moved? [grin]

Doing a postdoc at Berkeley. :)

M. Wilson Sayres · 17 February 2014

debunkingdenialism.com said:
For example, in mammals (even humans), the part of the Y chromosome that is most responsible for turning on the male-determining pathway doesn’t always function as it should, resulting in individuals with an X and a Y chromosome who have female physical characteristics
Most cases of androgen insensitivity syndrome is caused by a mutation in the androgen receptor. This receptor is encoded by a gene on the X chromosome, not Y (Chang et al, 1988).

I didn't mean to imply that most androgen receptor deficiencies are due to the Y, only that some can be. The study I linked to was specifically about identifying mutations in the SRY gene that reduced gene expression in SRY by half, which was sufficient to prevent SRY from regulating the androgen receptor pathway.

Paul Burnett · 17 February 2014

M. Wilson Sayres said:
Paul Burnett said: Ed Yong's article mentions "Melissa Wilson-Sayres from the University of Berkeley"! You've moved? [grin]
Doing a postdoc at Berkeley. :)

"University of California, Berkeley" - not "University of Berkeley"...right?

Robert Byers · 17 February 2014

Actually this fits a creationist model.
god only created souls. being male or female is entirely of the material world. Its the great division in biology. A common design result from a common plan.
Therefore our souls are not male or female. Yet we are profoundly, people, male or female. beyond the free will.
So it shows profound triggers must push profound conclusions in our thinking soon after birth.
darwin said women were intellectually biologically inferior to men.
yet investigation at such early stages of fetus development show its impossible for the brain thing to already have developed for male or female.
so its impossible for a intellectual difference based on genes since the genes are still up in the air about what sex its going to be.
Darwin was wrong and probably unlikely with the ladies.

phhht · 17 February 2014

Robert Byers said: Actually this fits a creationist model. god only created souls. being male or female is entirely of the material world. Its the great division in biology. A common design result from a common plan. Therefore our souls are not male or female. Yet we are profoundly, people, male or female. beyond the free will. So it shows profound triggers must push profound conclusions in our thinking soon after birth. darwin said women were intellectually biologically inferior to men. yet investigation at such early stages of fetus development show its impossible for the brain thing to already have developed for male or female. so its impossible for a intellectual difference based on genes since the genes are still up in the air about what sex its going to be. Darwin was wrong and probably unlikely with the ladies.

There are no gods, Byers, and nobody has a soul. Gods you're dumb.

M. Wilson Sayres · 18 February 2014

Paul Burnett said:
M. Wilson Sayres said:
Paul Burnett said: Ed Yong's article mentions "Melissa Wilson-Sayres from the University of Berkeley"! You've moved? [grin]
Doing a postdoc at Berkeley. :)
"University of California, Berkeley" - not "University of Berkeley"...right?

Ah, yes, yes, it should be UC Berkeley. Also, my last name isn't hyphenated. :)

wayneefrancis · 20 February 2014

Robert Byers said: Actually this fits a creationist model. god only created souls. being male or female is entirely of the material world. Its the great division in biology. A common design result from a common plan. Therefore our souls are not male or female. Yet we are profoundly, people, male or female. beyond the free will. So it shows profound triggers must push profound conclusions in our thinking soon after birth. darwin said women were intellectually biologically inferior to men. yet investigation at such early stages of fetus development show its impossible for the brain thing to already have developed for male or female. so its impossible for a intellectual difference based on genes since the genes are still up in the air about what sex its going to be. Darwin was wrong and probably unlikely with the ladies.

I seem to recall the bible saying that god created Adam and Eve. You can't just ignore major tenants of the bible and claim various scientific discoveries as a fit to the creationist model. There is no creationist model. Scientific models change when new information comes around scientist recognize that the old model was faulty. The models are most often recognized as faulty from the start and scientist strive to find better models. Compare this the the "models" creationist claim where they won't really commit to anything and when new discoveries are made they wave their hands and claim the "creationist model" fit this discovery the whole time and hope no one actually thinks more then .1 of a second about the actual statement. Name one prediction that was made from a "creationist model" that later came to be discovered as true. I'm not asking for a reinterpretation of some passage that can be loosely and often obscurely fit into something we have discovered. I want a "The scripture say X and because of this this we expect Y to happen at location Z" type of prediction and then show us where Y actually happened like it was predicted at location Z. This is what a model in science is used for. To make testable predictions that can be independently verified. Not to try to baselessly co-opt discoveries in science to try to illegitimately bolster the creationist position in the minds of the ignorant.

Robert Byers · 20 February 2014

wayneefrancis said:
Robert Byers said: Actually this fits a creationist model. god only created souls. being male or female is entirely of the material world. Its the great division in biology. A common design result from a common plan. Therefore our souls are not male or female. Yet we are profoundly, people, male or female. beyond the free will. So it shows profound triggers must push profound conclusions in our thinking soon after birth. darwin said women were intellectually biologically inferior to men. yet investigation at such early stages of fetus development show its impossible for the brain thing to already have developed for male or female. so its impossible for a intellectual difference based on genes since the genes are still up in the air about what sex its going to be. Darwin was wrong and probably unlikely with the ladies.
I seem to recall the bible saying that god created Adam and Eve. You can't just ignore major tenants of the bible and claim various scientific discoveries as a fit to the creationist model. There is no creationist model. Scientific models change when new information comes around scientist recognize that the old model was faulty. The models are most often recognized as faulty from the start and scientist strive to find better models. Compare this the the "models" creationist claim where they won't really commit to anything and when new discoveries are made they wave their hands and claim the "creationist model" fit this discovery the whole time and hope no one actually thinks more then .1 of a second about the actual statement. Name one prediction that was made from a "creationist model" that later came to be discovered as true. I'm not asking for a reinterpretation of some passage that can be loosely and often obscurely fit into something we have discovered. I want a "The scripture say X and because of this this we expect Y to happen at location Z" type of prediction and then show us where Y actually happened like it was predicted at location Z. This is what a model in science is used for. To make testable predictions that can be independently verified. Not to try to baselessly co-opt discoveries in science to try to illegitimately bolster the creationist position in the minds of the ignorant.

My example on sex selection here fits with the bible. All conclusions from the bible are true and so will prove true upon investigation where possible. much advancement could be made in science if biblical presumptions were accepted. I think the concept of the soul being only affected by the material world by way of the memory could lead to healing in many subjects.

DS · 21 February 2014

Your example on sex selection here has nothing to do with with the bible.
No scientific conclusions from the bible are true and so will never prove true upon investigation where possible.
much advancement has never been made in science using biblical presumptions were accepted.
you think the concept of the soul being only affected by the material world by way of the memory could lead to healing in many subjects but it has not and will not cause it's all just a bunch of made up malarchy
free yourself from the yolk of biblical presumptions and have the courage to examine the world as it actually is, otherwise you will reap what you don't sow

eric · 21 February 2014

Robert Byers said: much advancement could be made in science if biblical presumptions were accepted.

There ARE scientists that accept your presumptions (Behe and Dembski, for example). They have not advanced science at all, after 20+ years and god knows how much money they've been given. Why should anyone else use these presumptions when the people who use them now fail to make any discoveries? You seem to think that you're making a claim about the future (i.e., if only scientists would start doing this, scientific advancement would take off like a rocket). But people ARE doing what you suggest, right now, today, and when they do what you suggest, they fail to produce any scientific advances. Your hypothesis is wrong.

Just Bob · 21 February 2014

eric said:
Robert Byers said: much advancement could be made in science if biblical presumptions were accepted.
There ARE scientists that accept your presumptions (Behe and Dembski, for example). They have not advanced science at all, after 20+ years and god knows how much money they've been given. Why should anyone else use these presumptions when the people who use them now fail to make any discoveries? You seem to think that you're making a claim about the future (i.e., if only scientists would start doing this, scientific advancement would take off like a rocket). But people ARE doing what you suggest, right now, today, and when they do what you suggest, they fail to produce any scientific advances. Your hypothesis is wrong.

And a fair dinkum bunch of them give up on the 'biblical presumptions' when they discover they don't work, lead nowhere, and are just plain wrong. Robert, I've asked you (and other creationists) before, and never got an answer: Specifically WHAT advancements in science do you think we could make using a YEC model that we can't using the current 'materialistic' method? Any new cures? Miracle crops? A proof or disproof of string theory? Anything?

Henry J · 21 February 2014

Robert, I’ve asked you (and other creationists) before, and never got an answer: Specifically WHAT advancements in science do you think we could make using a YEC model that we can’t using the current ‘materialistic’ method? Any new cures? Miracle crops? A proof or disproof of string theory? Anything?

Cold fusion? Perpetual motion? Completely clean energy? Single stage to orbit? FTL travel? Climate stabilization?

eric · 21 February 2014

Just Bob said: WHAT advancements in science do you think we could make using a YEC model that we can't using the current 'materialistic' method? Any new cures? Miracle crops? A proof or disproof of string theory? Anything?