Departamento de Ciencias Biomédicas Básicas de la Facultad de Ciencias Biomédicas y de la Salud de la Universidad Europea de Madrid.

Is your favourite sportsman a sportswoman?

Biología CelularBC
Biología MolecularBM
Fisiología del ejercicioFE


Many of you reading this may not understand or even be aware of the huge controversy that occurs on a daily basis in sport today in regards to sex and gender. In many sports today tests have to be carried out before every major sporting event to test the sex of each athlete, in order for them to compete in a gender exclusive sporting fixture. This is commonly known as the “sex test”.

In athletics, a world of high stakes and high notoriety, its history is littered with cheats, forgoing honor and pride for the glory of victory. Unsurprisingly, men competing as women have been an issue in the Olympic Games. The first mandatory sex test was issued by the IAAF in 1950. Initially the test was a simple physical exam but was later replaced by a more dignifies method, cheek swabs to test for chromosomes XX and XY. However, gender isn’t as black and white as XX is a female and XY is a male. This has provided many ethical and thought provoking issues throughout the years.

The modern method of sex testing is looking at hormone levels. Hormone testing is believed to be more suitable than chromosome testing because the test doesn’t make any ‘determination of sex’ but instead looks at any unfair advantages from hormonal characteristics, such as increased muscle mass. There have been many cases of female athletes having hyperandrogenism. This is a medical condition identified by above normal levels of sex hormones, in this case testosterone. In 2014, Indian 100m and 200m athlete Dutee Chand failed a hormone test with testosterone levels that are normally only found in men. However, she was cleared to race by a landmark ruling and the validity of these gender tests was called into question (1).

The human body has 22 autosomal chromosomes, and these genetically code for pretty much most genetic features one might develop and inherit. The human body has an extra pair of chromosomes on top of this called the sex chromosomes, so normally each person has 46 chromosomes. When looking at the determination of sex, we look at the 2 types of possible sex chromosomes, X and Y. The grouping of these potential types of sex chromosomes will determine whether you are male, coded by XY chromosomes, or female, coded by XX.

All human life on this earth is a result of a sperm and an egg, but these actually differentiate from all other cells of the human body because in fact they only have one chromosome each, so these cells are called gametes. The male gamete, commonly known as a spermatozoon meets with the female’s gamete (egg), the egg fuses with it and forms a zygote. What actually determines the sex, is the fact that all the gametes that the female’s egg possess are X chromosomes, the only one changing variable is the fact that the male testes produces 50% gametes with X chromosome and 50% with Y chromosome. Depending on whether the first sperm to penetrate the glycoprotein layer of the egg is either X or Y, will result in the sex of the child (2).

The Barr body test is way of testing whether there are multiple X chromosomes in a cell i.e. when someone may be female. When a person has more than one X chromosome, one of them is active, whilst the other one is inactivated and condensed into something called “The Barr Body” (Figure 1). When a cell is in interphase, it can be stained in order to reveal the Barr Body. A woman who is XX will show one Barr Body, whilst a man who is XY will not show one at all. 

Nucleus of a female amniotic fluid cell showing the Barr Body
Figure 1. Nucleus of a female amniotic fluid cell showing the Barr Body. Left: Both X-chromosome territories are detected by FISH. Shown is a single optical section made with a confocal microscope. Right: Same nucleus stained with DAPI and recorded with a CCD camera. The Barr body is indicated by the arrow, it identifies the inactive X (Xi). 

In terms of sports, an athlete would be testing using the Barr Body Test, and if they did not show a Barr Body, then they would not qualify as a woman. The problem with this is that it assumes that all women must be XX and therefore only show one Barr Body, whilst all men are assumed to be XY and therefore will not show a Barr Body at all. You will see later on why this may not be the case. Another issue with the Barr Body test is that there is a condition called Mosaicism, in which all cells in a body may not all show the same genetic characteristics and therefore the results may not actually be the case! With this condition Mosaicism some cells in this person’s body will be XX, but other cells collected from the same body are XY! The only reason a person will appear to be a man or a woman depends on the proportion between the XY and XX cells (3).

It’s Not Their Fault!

Some women are perfectly eligible to compete in a specific sporting event, even though they tested negative for The Barr Body!  How you ask? Some women can be born with Turner’s Syndrome, this effectively means that they have only 45 chromosomes, and not 46 as you would expect (Figure 2). They are considered to be XO instead of XX, so they would actually test negative for a Barr Body because the one X chromosome they have is activated. Athletes who may have this condition are female, and would have no advantage in any sport.

Not surprisingly, it works the other way, and certain syndromes actually mean that men could compete in women’s sporting events! Klinefelter Syndrome means the person has 47 chromosomes, and whilst they do have 2 X chromosomes, they also have an extra Y chromosome meaning they are XXY (Figure 2). This means that even though they seem male and have male features due to their Y chromosome, they would still be allowed to compete as a woman according to the Barr Body test! (4).

Human karyotype
Figure 2. Human karyotype. Left:Turner Xyndrome (45, XO). Right: Klinefelter syndrome (47, XXY).

The issue of gender in athletics shines a light on the often arbitrary labels we assign to people. As we have seen, many of the tests and parameters that we use to determine gender aren’t valid in cases where genetic mutations disturb the normal makeup of what we perceive as man or woman, be it genetically or phenotypically. This is an issue that hasn’t reached an agreed conclusion and there is a lot of room for improvement in terms of testing and ethical standpoints.


1.    Clinical Trial Alert. Nephrology Times. 2009; 2(9):21-22.
2.    Science L. Chromosomes: Definition & Structure [Internet]. Live Science. 2017 [cited 28 May 2017]. Available from:
3.    Barr Body Testing [Internet]. Controversies in Biology and Society. 2017 [cited 28 May 2017]. Available from:
4.    Qinjie T, Fangfang H, Yuanzheng Z, Qinsheng G. Gender verification in athletes with disorders of sex development. Gynecological Endocrinology. 2009; 25(2):117-121.


Oliver Verghese, Neil Kohli, Rohin Patel, Youssef Tawil, Ludovica Oreglia. Estudiantes de 1º de Odontología. UEM. Curso 2016-2017. utiliza cookies propias y de terceros para su funcionamiento. Para más información sobre las cookies utilizadas consulta nuestra