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libby Moxey
03/12/2025
Psychology
Atypical sex development notes
105
•
3 Dec 2025
•
Ever wondered what happens when biological sex development doesn't follow... Show more
Your biology textbooks tell you that XX chromosomes mean female and XY chromosomes mean male, but it's actually more complex than that. The real game-changer is the SRY gene, typically found on the Y chromosome, which acts like a biological switch determining male development.
Here's where it gets interesting: even someone with XY chromosomes will develop as female if they don't have the SRY gene. This shows that chromosomes alone don't determine everything - it's the specific genes and hormones that matter most.
Testosterone drives male development whilst oestrogen guides female development. When these hormonal processes go differently than expected, we see atypical sex development patterns that teach us loads about how biology influences gender identity.
Quick Check: Remember that the SRY gene is the key player, not just the chromosome pattern!
The Batista Boys from the Dominican Republic provide one of psychology's most fascinating examples of atypical development. These children had XY chromosomes but were missing dihydrotestosterone during prenatal development, causing them to appear female at birth.
Plot twist: when puberty hit, a surge of testosterone caused these children to develop male characteristics. Most remarkably, they naturally switched their gender identity to match their biological changes, living the rest of their lives as males.
This case study suggests there's real fluidity to gender identity and that biological factors play a crucial role. When their hormones changed their physical appearance, their sense of self changed too, supporting the idea that sex and gender are closely interrelated.
Key Insight: The Batista Boys show that gender identity can adapt when biological sex characteristics change dramatically.
Klinefelter's syndrome affects biological males who have an extra X chromosome, giving them XXY instead of the typical XY pattern. This creates a unique set of physical and psychological characteristics that impact daily life.
Physically, men with Klinefelter's often have reduced body hair, breast development, and coordination problems. Psychologically, they tend to struggle with language skills and reading, often appearing shy and passive with less interest in sexual activity.
The case of Ken Scott illustrates how late diagnosis can be problematic. He wasn't diagnosed until age 36, missing out on crucial early support. Research by Herlihy et al (2011) found that early diagnosis and treatment lead to much better outcomes for managing the syndrome.
Remember: Early intervention makes a massive difference for people with Klinefelter's syndrome.
Turner's syndrome occurs when biological females are missing one X chromosome, leaving them with just a single X. This creates quite different challenges compared to Klinefelter's syndrome.
Women with Turner's syndrome typically don't menstruate or develop breasts naturally, and often struggle with infertility. However, they usually have strong reading abilities, though spatial and mathematical tasks can be more challenging.
Psychologists study these conditions because they provide natural experiments about how chromosomal differences affect gender expression and behaviour. By comparing people with atypical development to typical patterns, researchers can better understand the relationship between biology and gender identity.
Exam Tip: Focus on how these conditions help psychologists understand the role of chromosomes in gender development - that's what examiners love to see!
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
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The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Ever wondered what happens when biological sex development doesn't follow the typical XX or XY pattern? Atypical sex development shows us how chromosomes and hormones can create fascinating variations in human development, challenging our understanding of sex and gender.
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Your biology textbooks tell you that XX chromosomes mean female and XY chromosomes mean male, but it's actually more complex than that. The real game-changer is the SRY gene, typically found on the Y chromosome, which acts like a biological switch determining male development.
Here's where it gets interesting: even someone with XY chromosomes will develop as female if they don't have the SRY gene. This shows that chromosomes alone don't determine everything - it's the specific genes and hormones that matter most.
Testosterone drives male development whilst oestrogen guides female development. When these hormonal processes go differently than expected, we see atypical sex development patterns that teach us loads about how biology influences gender identity.
Quick Check: Remember that the SRY gene is the key player, not just the chromosome pattern!
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The Batista Boys from the Dominican Republic provide one of psychology's most fascinating examples of atypical development. These children had XY chromosomes but were missing dihydrotestosterone during prenatal development, causing them to appear female at birth.
Plot twist: when puberty hit, a surge of testosterone caused these children to develop male characteristics. Most remarkably, they naturally switched their gender identity to match their biological changes, living the rest of their lives as males.
This case study suggests there's real fluidity to gender identity and that biological factors play a crucial role. When their hormones changed their physical appearance, their sense of self changed too, supporting the idea that sex and gender are closely interrelated.
Key Insight: The Batista Boys show that gender identity can adapt when biological sex characteristics change dramatically.
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Klinefelter's syndrome affects biological males who have an extra X chromosome, giving them XXY instead of the typical XY pattern. This creates a unique set of physical and psychological characteristics that impact daily life.
Physically, men with Klinefelter's often have reduced body hair, breast development, and coordination problems. Psychologically, they tend to struggle with language skills and reading, often appearing shy and passive with less interest in sexual activity.
The case of Ken Scott illustrates how late diagnosis can be problematic. He wasn't diagnosed until age 36, missing out on crucial early support. Research by Herlihy et al (2011) found that early diagnosis and treatment lead to much better outcomes for managing the syndrome.
Remember: Early intervention makes a massive difference for people with Klinefelter's syndrome.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Turner's syndrome occurs when biological females are missing one X chromosome, leaving them with just a single X. This creates quite different challenges compared to Klinefelter's syndrome.
Women with Turner's syndrome typically don't menstruate or develop breasts naturally, and often struggle with infertility. However, they usually have strong reading abilities, though spatial and mathematical tasks can be more challenging.
Psychologists study these conditions because they provide natural experiments about how chromosomal differences affect gender expression and behaviour. By comparing people with atypical development to typical patterns, researchers can better understand the relationship between biology and gender identity.
Exam Tip: Focus on how these conditions help psychologists understand the role of chromosomes in gender development - that's what examiners love to see!
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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Quotes from every main character
English LiteratureApp Store
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Sociology
Psychology