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Anne Arendt

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Heath Ogden

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Utah Code 68-3-S12.5 (effective May 1, 2024) defines male and female based on their biological reproductive systems. Male is described as “the characteristic of an individual whose biological reproductive system is of the general type that functions to fertilize the ova of a female.” Female is defined as “the characteristic of an individual whose biological reproductive system is of the general type that functions in a way that could produce ova.” It also notes that sex consists of multiple factors: sex and reproductive organ anatomy; chromosomal makeup; and endogenous hormone profiles. Utah Code 26B-8-S101 (effective Sept. 1, 2024) introduces a definition of intersex people based on chromosomal differences. Still, the distinction between male and female is not as straightforward as these laws suggest, nor is societal identification of gender, which is different from biological sex.

X and Y chromosomes explained

Biological sex is often oversimplified in education as determined solely by the presence of an X and Y chromosome (male) or two X chromosomes (female). While this explanation seems clear, it fails to reflect the complexity of chromosomal, hormonal and genetic sex.

Both the X and Y chromosomes carry genes influencing sex development, including traits and genitalia that may not align with traditional definitions. The X chromosome houses hundreds of genes, while the smaller Y chromosome contains fewer, including the SRY gene, which typically triggers male-associated development during embryogenesis. However, the Y chromosome also has other genes important for biological functions, adding to its complexity.

Sex is determined by the 23rd chromosome pair, but the XX/XY framework is only a general guide and doesn’t account for the full range of human variations. Intersex people often have differences in chromosomes, anatomy or hormones, challenging binary definitions. For instance, Klinefelter syndrome (XXY) and Turner syndrome (XO) involve atypical chromosomal arrangements, while androgen insensitivity syndrome (AIS) can result in people with XY chromosomes developing female traits due to differences in hormone sensitivity. These examples show that sex chromosomes are not always reliable predictors of physical traits or biological sex.

Prevalence of intersex conditions is around 1%-2% of the population!

Many people have X and Y chromosome variations, also called anomalies, abnormalities or aneuploidies. For example, Klinefelter syndrome results in an XXY configuration rather than the typical XY (male). The journal Ultrasound in Obstetrics and Gynecology estimates Klinefelter syndrome occurs in about 1 in 380 live male births. Below are conservative estimates of frequencies for these conditions from the Focus Foundation, although they also note that they believe under 25% are diagnosed:

X and Y chromosome variations in people assigned male at birth:

• 47,XXY (Klinefelter syndrome) 1 out of 650 live births.
• 47,XYY (Jacob’s syndrome) 1 out of 1,000 live births.
• 48,XXYY 1 out of 18,000 live births.

X chromosome variations in people assigned female at birth:

• 45,X (Turner syndrome) 1 in about 2,250 live births [National Library of Medicine].
• 47,XXX (trisomy X or triple X) 1 in about 950 live births [Cleveland Clinic].

These figures show that intersex variations are more common than many might think, even if not always identified or diagnosed.

Implications and interpretations

Chromosomal variations represent just one part of a broader spectrum of physical sex characteristics, including differences in reproductive or sexual anatomy. Disorders of sex development (DSDs) refer to congenital conditions where the development of chromosomal, gonadal or anatomical sex is atypical. These variations are part of the broader concept of intersex.

According to Intersex: MedlinePlus Medical Encyclopedia, intersex people are born with genetic, hormonal or physical characteristics that do not align with typical male or female definitions. Intersex people have diverse bodies and identities, often identifying as male, female or neither. Hormonal differences, while interconnected with chromosomal variations, further illustrate the complexity of intersex conditions by influencing how biological sex characteristics develop.

While chromosomal differences provide a biological foundation, hormonal influences are equally significant. Hormones like testosterone and estrogen regulate the development of secondary sex characteristics and reproductive anatomy. Differences in hormone levels or sensitivities, such as those observed in conditions like androgen insensitivity syndrome (AIS), contribute to the diversity of intersex traits. For example, 46/XY complete gonadal dysgenesis (women who are genetically men) illustrates hormonal and genetic variation, with documented cases of people with this condition even becoming pregnant and giving birth. These examples highlight that the binary model of sex, based solely on chromosomes or anatomy, is overly simplistic.

Defining male or female sex is rarely straightforward. Adding gender — encompassing identity, expression and lived experience — and sexual preferences further complicates matters. Binary classifications of sex and gender fail to capture the full diversity of human biology and experience. Recognizing this spectrum and approaching it with understanding is key. While binary configurations may be common, they are not definitive, and kindness in understanding this diversity is essential.

Anne Arendt is the associate dean of student affairs in the College of Engineering and Technology and a professor of technology management at Utah Valley University.

Heath Ogden is the department chair and a professor of biology in the College of Science at UVU.