logo
Please note!
This fact brief was originally published as an experiment to test the concepts behind fact briefs.
Readers should be aware that while there is still a lot of useful information in fact briefs like this one, not all of them reflect Gigafact's current methods and standards for fact briefs. If you come across any that you feel are out of date, don't hesitate to contact us at support@gigafact.org.
Brief Publisher Logo
FACT BRIEF

Can sex at birth always be identified through chromosomes alone?

By Lisa Freedland
Copy link
email
Copy featured image
email
NO

Research has concluded that the chromosome test historically used to determine sex-at-birth (in which embryos with XX chromosomes are identified as girls and embryos with XY chromosomes are identified as boys) isn't always accurate. Certain regulatory sequences in DNA enhance the development of an embryo's sex organs, making some sex tests more complicated.

A study in the journal Nature Communications concluded that so-called genetic “enhancers” control the development of testes and ovaries. Typically, the SRY gene and the Sox9 gene, both found on the Y chromosome, interact to develop testes. High Sox9 levels are needed for normal testis development. The research identified some cases where XX embryos had additional Sox9 copies and developed testes. Some XY embryos that had fewer Sox9 levels developed ovaries instead of testes.

This fact brief is responsive to conversations such as this one.
Sources
Science Daily: Geneticists make a new discovery about how a baby's sex is determined
Nature: Human sex reversal is caused by duplication or deletion of core enhancers
Science: Sex reversal following deletion of a single distal enhancer of Sox9
ABOUT THE CONTRIBUTOR
Gigafact
Between 2020 and 2022, under close editorial supervision, Gigafact contracted a group of freelance writers and editors to test the concepts for fact briefs and provide inputs to our software development process. We call this effort Gigafact Foundry. Over the course of these two years, Gigafact Foundry writers published over 1500 fact briefs in response to claims they found online. Their important work forms the basis of Gigafact formats and editorial guidelines, and is available to the public on Gigafact.org. Readers should be aware that while there is still a lot of relevant information to be found, not all fact briefs produced by Gigafact Foundry reflect Gigafact's current methods and standards for fact briefs. If you come across any that you feel are out of date and need to be looked at with fresh eyes, don't hesitate to contact us at support@gigafact.org.
FACT BRIEF BY
Brief Publisher Logo
Latest fact briefs
facebook
twitter
email
email
About fact briefs published on Gigafact
Fact briefs are short, credibly sourced summaries that offer “yes/no” answers in response to claims found online. They rely on publicly available, often primary source data and documents. Fact briefs are created by contributors to Gigafact —a nonprofit project looking to expand participation in fact-checking and protect the democratic process. See all fact briefs here.