NationStates Jolt Archive

I was pondering the existence of people who's physical appearance (naturally) doesn't reflect their chromosomal sex, as in XY females and XX males. As a result of that, I had to wonder if it's possible to get identical twins, who while sharing the same sex chromosomally, would end up with physically different sexes.

So, any thoughts?

(I could probably figure this out on my own by doing more research, but I'm lazy and what's the fun in that?)

I was pondering the existence of people who's physical appearance (naturally) doesn't reflect their chromosomal sex, as in XY females and XX males. As a result of that, I had to wonder if it's possible to get identical twins, who while sharing the same sex chromosomally, would end up with physically different sexes.
No. Identical twins are always maternal twins, and twins with different sexes cannot be "identical."

Identical twins, identical looks. Without surgery, at least.

Identical twins, identical looks.
bullshit

I was pondering the existence of people who's physical appearance (naturally) doesn't reflect their chromosomal sex, as in XY females and XX males. As a result of that, I had to wonder if it's possible to get identical twins, who while sharing the same sex chromosomally, would end up with physically different sexes.

So, any thoughts?

(I could probably figure this out on my own by doing more research, but I'm lazy and what's the fun in that?)
from what I understand it's not possible. I remember hearing a story about a set of identical twins who were implicated in a murder (well one of them was) only they couldn't really figure out which one did it because thier DNA was the same, so they couldn't charge either of them.

I have heard cases of people getting bone marrow transplants and ending up with two completely seperate sets of DNA at the same time (but that is off topic) like thier saliva and hair has one DNA profile but thier blood has another. ;)

from what I understand it's not possible. I remember hearing a story about a set of identical twins who were implicated in a murder (well one of them was) only they couldn't really figure out which one did it because thier DNA was the same, so they couldn't charge either of them.

so they couldn't even find fingerprints? :rolleyes:

so they couldn't even find fingerprints? :rolleyes:
I didn't get an entire copy of the case file, I only know what I read in the article. I would assume that they didn't have fingerprints or if they did they weren't good enough to match, or they were in one of the states that fingerprint evidence isn't admissable ect.

bullshit
Identical DNA, identical genes and gene expressions. Yes, there may be very slight differences, such as one might have a mole where the other doesn't, but in the case in question, where Kiwi-Kiwi asked about IDENTICAL twins showing DIFFERENT gender-type physical attributes, identical twins have the same gender-type attributes, and are therefore identical.

I didn't get an entire copy of the case file, I only know what I read in the article. I would assume that they didn't have fingerprints or if they did they weren't good enough to match, or they were in one of the states that fingerprint evidence isn't admissable ect.

There exist states that allow DNA evidence but not fingerprinting ? Why ?

There exist states that allow DNA evidence but not fingerprinting ? Why ?
Fingerprinting isn't scientific, there are no standards that are applied uniformly, some do a 3 point match, some an 8 point, there have been cases where one technologist thinks a partial print matches and others do not. It's not like DNA or a blood test that can be repeated every time with the same result.

I was pondering the existence of people who's physical appearance (naturally) doesn't reflect their chromosomal sex, as in XY females and XX males. As a result of that, I had to wonder if it's possible to get identical twins, who while sharing the same sex chromosomally, would end up with physically different sexes.

So, any thoughts?

(I could probably figure this out on my own by doing more research, but I'm lazy and what's the fun in that?)
If anyone has a Y chromosome in their genome then, regardless of how many X chromosomes they have, they will either be male or dead. Males who are 'XX' as you put it are most likely Kleinfelter Syndrome people, who are actually XXY (or variations upon the dual X) and show some female physical attributes e.g. breast formation, high cheekbones, feminine pubic hairline etc.

As for Hermaphroditism - strangely, the gender is not directly determined by the sex chromosomes. Hermaphrodites can be XX, XY, mosaic or Turner Syndrome. In every case except mosaic, the gender is assigned according to karotype. Even more strangely, the gender phenotype can be determined by an autosomal chromosome e.g. through Androgen Insensitivity Syndrome, where androgens are not stimulative to any or some tissue, sometimes leading to a female phenotype with a male genotype.

If anyone has a Y chromosome in their genome then, regardless of how many X chromosomes they have, they will either be male or dead. Males who are 'XX' as you put it are most likely Kleinfelter Syndrome people, who are actually XXY (or variations upon the dual X) and show some female physical attributes e.g. breast formation, high cheekbones, feminine pubic hairline etc.

As for Hermaphroditism - strangely, the gender is not directly determined by the sex chromosomes. Hermaphrodites can be XX, XY, mosaic or Turner Syndrome. In every case except mosaic, the gender is assigned according to karotype. Even more strangely, the gender phenotype can be determined by an autosomal chromosome e.g. through Androgen Insensitivity Syndrome, where androgens are not stimulative to any or some tissue, sometimes leading to a female phenotype with a male genotype.
can you re-explain that? My cold medicine isn't letting me understand without major googling.

If anyone has a Y chromosome in their genome then, regardless of how many X chromosomes they have, they will either be male or dead.
Not true. It is perfectly possible that somebody is an XY female. It's called Androgen Insensitivity Syndrome.

I was pondering the existence of people who's physical appearance (naturally) doesn't reflect their chromosomal sex, as in XY females and XX males. As a result of that, I had to wonder if it's possible to get identical twins, who while sharing the same sex chromosomally, would end up with physically different sexes.

So, any thoughts?

(I could probably figure this out on my own by doing more research, but I'm lazy and what's the fun in that?)

All I know is that would be a couple of odd looking babies if they were identicle twins and opposite sexes.

Yes, yes ... but which one is the evil one?

can you re-explain that? My cold medicine isn't letting me understand without major googling.
Heh. I just re-read it and realised it was as if my lecture notes were written down poorly. OK.

I think the first bit is fairly obvious - if somebody has a Y-chromosome in the majority of cells in their body, they cannot be female. If they are XY, they are male. If they are XXY/XXXY/XXYY/XYY, they are male. If they are YO (only have a Y chromosome, no complimentary X), they will not survive.

These people may not be 'typical' males - multiple X chromosomes often result in feminine attributes such as breasts and the female pubic line, multiple Y chromosomes (coupled with only one X) will often show hypermale attributes (more competitive, stronger possibly, however reduced genital size is often prominent). All non-standard forms have a highly increased chance of mental retardation.

With hermaphrodites, there isn't a set karotype (chromosome layout) that defines their phenotypes (how they look/how their bodies work). You can be hermaphrodite with a standard sex chromosome layout (XX/XY), Turner Syndrome (only one X chromosome) or with a mosaic layout (where your body cells vary in their sex chromosome layout). Often, Kleinfelter Sydrome patients (male with multiple X chromosomes) can be mistaken for Hermaphrodites, but I don't think they fall into that category.

The Androgen Insensitivity Syndrome part - Androgens are the 'male' hormones e.g. those which are more prevalent in the formation of male characteristics. Among others, this group includes testosterone. If males have an allele/combination of alleles (which IIRC isn't on the sex chromosomes, but instead one of the autosomal, non-sex chromosomes) that either stops the formation of testosterone or prevents the detection of testosterone, then the person may form female genitalia and external characteristics regardless of the fact that they are male. Since testosterone is needed in formation of the ovaries, though, they will be sterile.

In relation to the first post - I would suggest it is very rare for identical twins to be opposite genders. The only idea I can think of is that one of the embryos suffersa very early mutation i.e. the loss of a Y chromosome in a proportion of their cells (i.e. mosaicism with XY individual leading to some of their cells being normal while some are XO) which may result in one individual being male and the other possibly a combination of male and Turner's syndrome.

Not true. It is perfectly possible that somebody is an XY female. It's called Androgen Insensitivity Syndrome.
They aren't female. Their phenotype is female, yes, but the fact that they have a Y chromosome is what defines them as male. The AIS genes are, I think, autosomal traits, hence they actually have nothing to do with gender.

EDIT: I am, of course, talking entirely from a mammalian biological perspective. If we are moving into the realm of ethics, it depends upon whether you define a trangendered person as male or female (depending upon original sex). By some people's definitions yes, CAIS and PAIS people could be defined as female. As a biochemist and geneticist, I define them as male, if only for the fact that I look at the nuclear level and its effects upon appearance and function.

can you re-explain that? My cold medicine isn't letting me understand without major googling.

Hermaphroditism/pseudo-hermaphroditism- Occurs when there are abnormalities in cell division. They may have both cells with 46 XY (male) chromosomes and cells with 46 XX (female) chromosomes.

Turners Syndrome- Turner syndrome results from 100% of cells lacking an X chromosome.

Chromosomal mosaicism- Some cells may have 47 chromosomes (such as extra chromosome 21 or X chromosome in some, but not all cells). You can determine sex via karyotyping (chromosome analysis). The test is normally done 2-3 times to verify...

Autosomal chromosome (http://www.medterms.com/script/main/art.asp?articlekey=20693)- Any chromosome except for the sex chromosomes. Humans have 44 autosomal chromosomes, or autosomes.

Androgen Insensitivity Syndrome/AIS/ARS/CAIS (http://en.wikipedia.org/wiki/Androgen_insensitivity_syndrome)- Ex: A woman who physically looks female, with a 46XY karyotype and the presence of testes.

Heh. I just realised - I've never seen an NS thread so apt for my course :D

Androgen Insensitivity Syndrome/AIS/ARS/CAIS (http://en.wikipedia.org/wiki/Androgen_insensitivity_syndrome)- Ex: A woman who physically looks female, with a 46XY karyotype and the presence of testes.
I think that CAIS XY doesn't even exhibit testes.

I think that CAIS XY doesn't even exhibit testes.

I'm wrong, my brain is fried from studying for my last final (Neuroendo exam....) :)

Though a proper diagnosis of AIS/PAIS would be: 46XY karyotype, increased T, normal conversion of T to DHT, defective andro-binding of genital fibroblasts, increased LH, and PN elevations in LH and T, right? In CAIS it would be reduced LH correct?

I was pondering the existence of people who's physical appearance (naturally) doesn't reflect their chromosomal sex, as in XY females and XX males. As a result of that, I had to wonder if it's possible to get identical twins, who while sharing the same sex chromosomally, would end up with physically different sexes.

So, any thoughts?

(I could probably figure this out on my own by doing more research, but I'm lazy and what's the fun in that?)

Technically,the answer is yes. If a zygote was formed that was male, and then split into twins, one of the twins could develop Turner's Syndrome. This would occur if an improper division occurred so that most of the embryo's cells would become XO instead of XY. Thus, the twins would be monozygotic (identical/maternal), but one would be physically male and the other would appear physically female (although she may have undescended testis that would have to be removed later in life.)

I'm wrong, my brain is fried from studying for my last final (Neuroendo exam....) :)

Though a proper diagnosis of AIS/PAIS would be: 46XY karyotype, increased T, normal conversion of T to DHT, defective andro-binding of genital fibroblasts, increased LH, and PN elevations in LH and T, right? In CAIS it would be reduced LH correct?
Unfortunately when it comes to AIS, my own knowledge is limited to what I've researched in the last half an hour, with a little from lectures in no detail. From what I can make of the whole situation, AIS can take two different basic forms - a defect in conversion of cholesterol to testosterone or a defect in formation of testosterone receptors. I shall have a look through my text books, though, brb.

Unfortunately when it comes to AIS, my own knowledge is limited to what I've researched in the last half an hour, with a little from lectures in no detail. From what I can make of the whole situation, AIS can take two different basic forms - a defect in conversion of cholesterol to testosterone or a defect in formation of testosterone receptors. I shall have a look through my text books, though, brb.

I suppose I could also look through my texts, but since you're so willing to do it :)........

A lot of this was 1st year stuff, I just don't remember some of it, blah.

I was pondering the existence of people who's physical appearance (naturally) doesn't reflect their chromosomal sex, as in XY females and XX males. As a result of that, I had to wonder if it's possible to get identical twins, who while sharing the same sex chromosomally, would end up with physically different sexes.

So, any thoughts?

(I could probably figure this out on my own by doing more research, but I'm lazy and what's the fun in that?)


it can't be possible one would have a penis and the other wouldn't

I suppose I could also look through my texts, but since you're so willing to do it :)........

A lot of this was 1st year stuff, I just don't remember some of it, blah.
Bah. Stupid bloody text books. £180 worth of useless paper, IMO.

Translation: there was one mention of AIS in one text book. In one table.

it can't be possible one would have a penis and the other wouldn't
Summation of this thread - in XX/XY then yes, that's true. With the XY/XO possibility then it could happen.

Bah. Stupid bloody text books. £180 worth of useless paper, IMO.

Translation: there was one mention of AIS in one text book. In one table.

All I know is that there is: MAIS, PAIS, Reifenstein syndrome, CAIS :)

it can't be possible one would have a penis and the other wouldn't

Quite. That was kind of the point. Genetically identical (mostly identical?) twins with different apparent sexes.

To everyone else: Thanks for the information! I was thinking that it probably wasn't really possible, but I wanted to know for sure.

I suppose this means that in that story idea of mine, the twins are either going to be fraternal or the result of supernatural causes...

Quite. That was kind of the point. Genetically identical (mostly identical?) twins with different apparent sexes.
They would be genetically non-identical but still conform to the 'identical twins' definition (being the result of the fertilisation of one sperm and one egg). Also, Turner Syndrome people often suffer from mental retardation IIRC, plus the stunted growth and such.

All I know is that there is: MAIS, PAIS, Reifenstein syndrome, CAIS :)

PAIS is partial androgen insensitivity syndrome. Generally it is a defect in the androgen receptors that doesn't completely block their response, but mostly does. I'm not very familiar with the way it presents.

CAIS is complete androgen insensitivity syndrome. The receptors simply will not respond to androgens. Thus, in development, all the hormones that would normally be produced in a developing male will be produced, but will be ignored by the receptors. Since the default is female, the baby is born apparently female, despite the existence of an XY genotype.

I'm not familiar with the other two.

They would be genetically non-identical but still conform to the 'identical twins' definition (being the result of the fertilisation of one sperm and one egg). Also, Turner Syndrome people often suffer from mental retardation IIRC, plus the stunted growth and such.

Ah. I understand. I'm actually researching sex chromosome disorders for Biology right now, so I know a bit about Turner Syndrome.

Seriously though, thanks for the information. This was really something that's been annoying me for a while.

PAIS is partial androgen insensitivity syndrome. Generally it is a defect in the androgen receptors that doesn't completely block their response, but mostly does. I'm not very familiar with the way it presents.

CAIS is complete androgen insensitivity syndrome. The receptors simply will not respond to androgens. Thus, in development, all the hormones that would normally be produced in a developing male will be produced, but will be ignored by the receptors. Since the default is female, the baby is born apparently female, despite the existence of an XY genotype.

I'm not familiar with the other two.

Indeed, I had to study all this stuff 1st year, icky.

MAIS- Mild AIS (undervirilized male syndrome). Unambiguously male external genitalia. Undermasculinization. Runs in families.

Reifenstein syndrome- Partial AIS with ambiguous genitalia or predominantly male genitalia.

Heh. I just re-read it and realised it was as if my lecture notes were written down poorly. OK.

I think the first bit is fairly obvious - if somebody has a Y-chromosome in the majority of cells in their body, they cannot be female. If they are XY, they are male. If they are XXY/XXXY/XXYY/XYY, they are male. If they are YO (only have a Y chromosome, no complimentary X), they will not survive.

These people may not be 'typical' males - multiple X chromosomes often result in feminine attributes such as breasts and the female pubic line, multiple Y chromosomes (coupled with only one X) will often show hypermale attributes (more competitive, stronger possibly, however reduced genital size is often prominent). All non-standard forms have a highly increased chance of mental retardation.

With hermaphrodites, there isn't a set karotype (chromosome layout) that defines their phenotypes (how they look/how their bodies work). You can be hermaphrodite with a standard sex chromosome layout (XX/XY), Turner Syndrome (only one X chromosome) or with a mosaic layout (where your body cells vary in their sex chromosome layout). Often, Kleinfelter Sydrome patients (male with multiple X chromosomes) can be mistaken for Hermaphrodites, but I don't think they fall into that category.

The Androgen Insensitivity Syndrome part - Androgens are the 'male' hormones e.g. those which are more prevalent in the formation of male characteristics. Among others, this group includes testosterone. If males have an allele/combination of alleles (which IIRC isn't on the sex chromosomes, but instead one of the autosomal, non-sex chromosomes) that either stops the formation of testosterone or prevents the detection of testosterone, then the person may form female genitalia and external characteristics regardless of the fact that they are male. Since testosterone is needed in formation of the ovaries, though, they will be sterile.

In relation to the first post - I would suggest it is very rare for identical twins to be opposite genders. The only idea I can think of is that one of the embryos suffersa very early mutation i.e. the loss of a Y chromosome in a proportion of their cells (i.e. mosaicism with XY individual leading to some of their cells being normal while some are XO) which may result in one individual being male and the other possibly a combination of male and Turner's syndrome.

Thank you, that was much clearer. I understand now. Thanks for re-explaining:)

Yes, yes ... but which one is the evil one?
I am ;)