Diversity in sex development | AQA A-Level Psychology Revision

Revision Notes
Aug 5
17 min read

Updated: 6 hours ago

For 7182 specification, first teach in September 2025

AQA A-Level Psychology | Free Revision Notes

Estimated study time: 55 minutes

Diversity in sex development refers to variations in chromosomes, hormones or the body’s response to hormones that affect sexual development. These Diversity in sex development A-Level Psychology revision notes cover androgen insensitivity syndrome, Klinefelter’s syndrome and Turner syndrome. The conditions demonstrate why biological sex cannot always be predicted from an XXXXXX or XYXYXY chromosome pattern alone. This lesson brings together sex chromosome patterns and hormonal influences on development. AQA requires knowledge of all three named conditions.

Learning Objectives 🎯

By the end of this revision page, you should be able to:

Define diversity in sex development.
Describe androgen insensitivity syndrome.
Describe Klinefelter’s syndrome and its XXYXXYXXY chromosome pattern.
Describe Turner syndrome and its X0X0X0 chromosome pattern.
Compare the chromosomal and hormonal processes involved in the three conditions.
Explain how these conditions contribute to a more complete understanding of biological sex.

Revision Notes 📚

Diversity in sex development A-Level Psychology revision overview

Diversity in sex development, often abbreviated to DSD, refers to variations in biological characteristics involved in sexual development.

These characteristics may include:

Sex chromosomes.
Genes affecting sexual development.
Gonads, such as testes or ovaries.
Hormone production.
The body’s sensitivity to hormones.
Internal or external sexual characteristics.

The three examples named in the AQA specification are:

Androgen insensitivity syndrome
Klinefelter’s syndrome
Turner syndrome

These conditions show that biological sex development involves an interaction between several biological processes.

Chromosomes influence development, but chromosomes do not act alone.

Specification focus

The AQA specification names the three conditions but does not prescribe a fixed checklist of every possible characteristic. Revision should therefore prioritise:

The chromosome pattern involved.
The hormonal or developmental mechanism.
The typical direction of sexual development.
The main associated characteristics.
What the condition demonstrates about biological sex.

Typical biological sex development

Before studying DSD, it is useful to recall the typical developmental pathways.

Typical XYXYXY development

The person has an XYXYXY chromosome pattern.
The YYY chromosome normally contains the SRY gene.
The SRY gene initiates the development of testes.
The testes produce androgens, including testosterone.
Body tissues respond to the androgens.
Typically male sexual characteristics develop.

Typical XXXXXX development

The person has an XXXXXX chromosome pattern.
There is normally no YYY chromosome or SRY gene.
Ovaries develop.
Oestrogen contributes to typically female sexual development.
Typically female sexual characteristics develop.

DSD may occur when:

A sex chromosome is additional or absent.
Gonads develop differently.
Hormone production differs.
Body tissues do not respond typically to a hormone.

Biological sex has several components

Biological sex is not represented by one single characteristic.

Component	What it concerns
Chromosomal pattern	Sex chromosomes such as XXXXXX, XYXYXY, XXYXXYXXY or X0X0X0
Genetic activity	Genes such as SRY that influence gonadal development
Gonadal development	Development of testes or ovaries
Hormone production	Production of androgens or oestrogen
Hormone sensitivity	Whether body tissues respond to the hormones produced
Sexual anatomy	Internal and external sexual characteristics

In typical development, these components usually follow one of two common pathways. DSD demonstrates that they do not always align in the expected way.

Androgen insensitivity syndrome

What is androgen insensitivity syndrome?

Androgen insensitivity syndrome, abbreviated to AIS, occurs when a person with an XYXYXY chromosome pattern is partly or completely unable to respond to androgens.

Androgens are hormones involved in typically male sexual development. Testosterone is an important example.

A person with AIS usually has:

An XYXYXY chromosome pattern.
A YYY chromosome containing the SRY gene.
Testes that produce androgens.
Body tissues that respond partly or not at all to those androgens.

The central problem is not necessarily that androgens are absent. The body is insensitive to their effects.

The biological process in AIS

The process can be followed step by step.

The person has an XYXYXY chromosome pattern.
The SRY gene initiates testicular development.
The testes produce androgens.
Receptors in body tissues do not respond typically to those androgens.
Typically male external sexual development is reduced or does not occur.

This can be summarised as:

XYXYXY chromosomes + testes + androgens + androgen insensitivity = development that differs from the typical XYXYXY pathway

Complete androgen insensitivity

In complete androgen insensitivity syndrome, body tissues do not respond to androgens.

The person usually:

Has an XYXYXY chromosome pattern.
Has testes, which may be located internally.
Develops typically female external sexual characteristics.
Is usually assigned female at birth.
Does not develop a uterus in the typical way.
Does not menstruate.
Is infertile.

The person may not learn that they have an XYXYXY chromosome pattern until puberty, particularly if medical investigation begins because menstruation has not started.

Partial androgen insensitivity

In partial forms of AIS, body tissues respond to androgens to a limited extent.

Sexual development may therefore include a mixture of characteristics typically associated with male and female development.

The key examination point is that androgen sensitivity can vary. It is not simply a choice between complete sensitivity and complete insensitivity.

AIS and hormone receptors

Hormones affect only tissues with functioning receptors that respond to them.

A hormone can be present in the bloodstream but have a reduced effect when:

The relevant receptor does not function typically.
The tissue cannot detect the hormone.
The biological response is incomplete.

AIS therefore demonstrates that hormone action depends on both:

hormone production + hormone sensitivity

This is a crucial distinction.

Applying AIS to a scenario

Consider the following scenario:

Genetic testing shows that Taylor has an XYXYXY chromosome pattern. Taylor has internal testes that produce androgens but developed typically female external sexual characteristics because body tissues did not respond to the hormones.

A developed explanation would state that:

Taylor has an XYXYXY chromosome pattern.
The SRY gene initiated testicular development.
The testes produced androgens.
Taylor’s tissues were insensitive to those androgens.
Typical male external development therefore did not occur.
The pattern is consistent with androgen insensitivity syndrome.

What AIS shows about biological sex

AIS demonstrates that an XYXYXY chromosome pattern is not sufficient by itself to produce typical male external development.

Typical development also depends on:

The SRY gene functioning.
Testes developing.
Androgens being produced.
Body tissues responding to the androgens.

AIS therefore challenges an overly simple statement such as:

“Everyone with XYXYXY chromosomes develops typical male characteristics.”

A more accurate statement is:

“An XYXYXY chromosome pattern normally initiates male development, but the outcome also depends on hormone production and hormone sensitivity.”

Klinefelter’s syndrome

What is Klinefelter’s syndrome?

Klinefelter’s syndrome occurs when a person has an additional XXX chromosome.

The chromosome pattern is:

XXYXXYXXY

The person has:

Two XXX chromosomes.
One YYY chromosome.

A person with Klinefelter’s syndrome normally develops as male because the YYY chromosome usually contains the SRY gene.

AQA mark schemes identify XXYXXYXXY as an atypical chromosome pattern associated with male development.

The biological process in Klinefelter’s syndrome

The process can be understood as follows:

The person has an XXYXXYXXY chromosome pattern.
The YYY chromosome normally contains the SRY gene.
The SRY gene initiates the development of testes.
The person therefore develops in a typically male direction.
The additional XXX chromosome affects testicular and hormonal development.
Testosterone levels may be lower than in typical XYXYXY development.

The presence of two XXX chromosomes does not mean that the person develops as female.

The YYY chromosome and SRY gene remain highly influential.

Characteristics associated with Klinefelter’s syndrome

Possible physical characteristics include:

Greater than average height.
Small testes.
Lower testosterone production.
Reduced facial or body hair.
Limited development of some typically male secondary sexual characteristics.
Possible breast development.
Infertility.

Possible cognitive or behavioural characteristics identified in AQA materials include:

Difficulties with reading or writing.
A tendency towards emotional upset.
Passivity.

These are possible associations rather than characteristics experienced identically by every person. The AQA mark scheme highlights increased height, small testes, reduced facial hair and some reading or writing difficulties.

Klinefelter’s syndrome and testosterone

The testes may not function in the typical way, so testosterone production can be reduced.

Lower testosterone may contribute to:

Reduced facial and body hair.
Less pronounced development of some secondary sexual characteristics.
Reduced fertility.

This illustrates an important interaction:

chromosome variation → gonadal development → hormone production → physical characteristics

The additional chromosome affects development partly through its influence on the testes and hormone levels.

Applying Klinefelter’s syndrome to a scenario

Consider the following scenario:

A person is taller than average, has small testes and produces less testosterone than is typical for males. Genetic testing identifies two XXX chromosomes and one YYY chromosome.

A strong application would explain that:

The chromosome pattern is XXYXXYXXY.
This is associated with Klinefelter’s syndrome.
The YYY chromosome normally contains the SRY gene.
The person therefore develops as male.
The additional XXX affects testicular development and testosterone production.
This can help explain the person’s physical characteristics.

What Klinefelter’s syndrome shows about biological sex

Klinefelter’s syndrome demonstrates that:

Two XXX chromosomes do not automatically produce female development.
The presence of the YYY chromosome and SRY gene normally initiates male development.
Additional chromosomes can influence the degree to which sexual characteristics develop.
Chromosomal sex and physical development are related but not identical concepts.

It also shows that a chromosome pattern can influence development indirectly through hormone production.

Turner syndrome

What is Turner syndrome?

Turner syndrome occurs when a person has one XXX chromosome and no second sex chromosome.

The pattern may be written as:

X0X0X0

It is also commonly written as XOXOXO. The second symbol represents the absence of a sex chromosome rather than the letter OOO.

A person with Turner syndrome develops as female.

AQA mark schemes identify Turner syndrome as a female developmental pattern involving a missing XXX chromosome.

The biological process in Turner syndrome

The process can be understood as follows:

The person has one XXX chromosome.
There is no YYY chromosome.
There is normally no SRY gene.
Testicular development is not initiated.
The person develops in a female direction.
The absence of the second sex chromosome affects ovarian development and oestrogen production.

Turner syndrome therefore shows that one XXX chromosome can support female development, although the second sex chromosome is important for typical ovarian and reproductive development.

Characteristics associated with Turner syndrome

Possible physical characteristics include:

Shorter than average stature.
Ovaries that do not develop typically.
Reduced oestrogen production.
Limited breast development without hormone treatment.
Limited development of some secondary sexual characteristics.
Infertility.

Possible cognitive characteristics identified in AQA material include relatively strong:

Language skills.
Reading skills.

Again, characteristics vary between individuals. AQA’s 2022 mark scheme identifies shorter stature, limited breast development, infertility and relatively good language or reading skills as possible features.

Turner syndrome and oestrogen

Ovarian development is often limited, which can reduce the production of oestrogen.

Lower oestrogen can affect:

Pubertal development.
Secondary sexual characteristics.
Menstruation.
Fertility.

Turner syndrome therefore illustrates how a chromosomal variation can influence biological sex through its effect on gonads and hormones.

Applying Turner syndrome to a scenario

Consider the following scenario:

Genetic testing shows that Morgan has one XXX chromosome and no second sex chromosome. Morgan developed as female but has underdeveloped ovaries, low oestrogen and limited pubertal development.

A developed application would explain that:

The chromosome pattern is X0X0X0.
This is associated with Turner syndrome.
There is no YYY chromosome or SRY gene.
Male development is therefore not initiated.
The missing second sex chromosome affects ovarian development.
Reduced ovarian functioning leads to lower oestrogen and limited secondary sexual development.

What Turner syndrome shows about biological sex

Turner syndrome demonstrates that:

Two XXX chromosomes are not required for development in a female direction.
The absence of a YYY chromosome normally means that male development is not initiated.
The second sex chromosome is nevertheless important for typical ovarian and reproductive development.
Chromosome number can affect hormone production and sexual characteristics.

Comparing the three conditions

Feature	Androgen insensitivity syndrome	Klinefelter’s syndrome	Turner syndrome
Typical chromosome pattern	XYXYXY	XXYXXYXXY	X0X0X0
YYY chromosome present?	Yes	Yes	No
SRY gene normally present?	Yes	Yes	No
Testes develop?	Usually yes	Yes, but development may be affected	No
Main biological difference	Tissues do not respond typically to androgens	Additional XXX affects testes and testosterone	Missing second sex chromosome affects ovaries and oestrogen
Typical developmental direction	Female external development in complete AIS	Male	Female
Main lesson	Hormone sensitivity matters	A YYY chromosome remains influential despite two XXX chromosomes	One XXX can support female development, but ovarian development is affected

A comparison by biological level

The three conditions affect different points in the developmental pathway.

AIS affects hormone response

Chromosomes: usually XYXYXY.
Gonads: testes develop.
Hormones: androgens are produced.
Difference: body tissues do not respond typically.

Klinefelter’s syndrome affects chromosome number and hormone production

Chromosomes: XXYXXYXXY.
Gonads: testes develop.
Hormones: testosterone may be lower.
Difference: an additional XXX affects development.

Turner syndrome affects chromosome number and ovarian development

Chromosomes: X0X0X0.
Gonads: ovaries do not develop typically.
Hormones: oestrogen may be lower.
Difference: the second sex chromosome is absent.

Memory structure

A useful revision pattern is:

AIS: XYXYXY, but androgens cannot act typically.
Klinefelter’s: XXYXXYXXY, male development with an additional XXX.
Turner: X0X0X0, female development with a missing sex chromosome.

📌 Exam tip: Learn more than the chromosome patterns. A strong answer links each pattern to gonads, hormones and physical development.

How DSD contributes to understanding biological sex

Biological sex is not determined by chromosomes alone

The three conditions show that chromosome pattern is one part of biological sex development.

AIS provides the clearest example:

The person has XYXYXY chromosomes.
The SRY gene initiates testicular development.
Androgens are produced.
Typical male external development does not occur because tissues cannot respond.

A chromosome-only account cannot explain this outcome.

Hormone sensitivity is as important as hormone presence

It is not enough for a hormone to be present.

For a hormone to have its typical effect:

The hormone must be produced.
It must reach the relevant body tissues.
The tissues must contain functioning receptors.
The tissues must respond to the hormone.

AIS demonstrates what happens when the final stage is disrupted.

The YYY chromosome has an important but not absolute role

Klinefelter’s syndrome demonstrates the importance of the YYY chromosome.

Although a person has two XXX chromosomes:

The YYY chromosome normally carries the SRY gene.
Testes develop.
Male development is initiated.

However, AIS shows that the YYY chromosome does not guarantee every typically male characteristic.

The YYY chromosome initiates a pathway whose later stages must also function.

The number of XXX chromosomes affects development

Turner syndrome and Klinefelter’s syndrome show that variations in the number of XXX chromosomes have biological effects.

A missing XXX affects ovarian and reproductive development.
An additional XXX affects testicular and hormonal development.

The XXX chromosome therefore contributes to more than simply identifying an individual as typically female or male.

Biological sex is multidimensional

DSD supports a multidimensional view of biological sex.

A person may be described in relation to:

Chromosomes.
Gonads.
Hormone levels.
Hormone sensitivity.
Internal anatomy.
External anatomy.

These dimensions usually align in typical XXXXXX and XYXYXY development, but DSD demonstrates that they can vary independently.

This does not mean chromosomes or hormones are unimportant. It means biological sex emerges from their interaction.

DSD challenges an overly simple binary account

Most people develop through typical XXXXXX or XYXYXY pathways.

However, DSD shows that not every person fits a simple rule in which:

XXXXXX always produces one fixed set of characteristics.
XYXYXY always produces another fixed set.

Biological sex remains grounded in biological characteristics, but those characteristics show natural variation.

A scientifically accurate account must recognise typical patterns without treating them as the only possible patterns.

Biological sex and gender identity remain distinct

DSD concerns biological development.

It does not automatically determine:

A person’s gender identity.
Whether they identify as binary or non-binary.
Their masculinity or femininity.
Their interests or personality.
Their preferred gender role.

The distinction between biological characteristics and identity is developed in binary, non-binary and gender-fluid identities.

A person’s chromosome pattern should not be used to make unsupported assumptions about how they understand or describe their gender.

DSD and biological explanations of gender development

The three conditions may also inform chromosome-based and hormonal explanations.

They demonstrate that biological explanations should consider:

More than chromosome labels.
The interaction of genes and hormones.
Hormone receptors and sensitivity.
Variation between individuals.

An explanation that reduces gender development to XXXXXX or XYXYXY alone is therefore biologically incomplete.

DSD and reductionism

A biologically reductionist explanation attempts to explain a complex outcome using a single lower-level biological factor.

For example:

“An XYXYXY chromosome pattern inevitably produces typical male development.”

AIS shows why this is too reductionist. The explanation ignores androgen receptors and hormone sensitivity.

A less reductionist biological account considers the full pathway:

chromosomes → genes → gonads → hormones → hormone sensitivity → sexual characteristics

This issue can be explored further through levels of explanation in Psychology.

DSD and social sensitivity

Research and teaching about DSD are socially sensitive.

Descriptions may influence:

How individuals with DSD are perceived.
Medical and social decisions.
Expectations about identity and behaviour.
Attitudes towards variation in sexual development.

Psychologists should therefore:

Use accurate terminology.
Avoid presenting people as examination curiosities.
Avoid assuming that everyone has identical experiences.
Distinguish biological characteristics from identity.
Avoid using words such as “abnormal” when “variation” is more precise.

This connects with the consequences of socially sensitive research.

Applying DSD knowledge in examinations

Identifying the correct condition

Use these diagnostic questions.

Is the chromosome pattern XYXYXY, but the body does not respond to androgens?

This indicates androgen insensitivity syndrome.

Is the chromosome pattern XXYXXYXXY?

This indicates Klinefelter’s syndrome.

Is there one XXX chromosome and no second sex chromosome?

This indicates Turner syndrome.

Developing an answer

A weak answer states:

“The person has Klinefelter’s syndrome.”

A developed answer states:

“The person has an XXYXXYXXY chromosome pattern, which is associated with Klinefelter’s syndrome. The YYY chromosome normally contains the SRY gene, so testes develop and the person develops as male. However, the additional XXX can affect testicular functioning and reduce testosterone production.”

Application answer structure

Use:

chromosome pattern → biological mechanism → developmental outcome → condition

For AIS:

XYXYXY → testes and androgen production → tissues cannot respond → female external development in complete AIS

For Klinefelter’s syndrome:

XXYXXYXXY → SRY initiates testes → reduced testicular functioning or testosterone → male development with associated variations

For Turner syndrome:

X0X0X0 → no SRY → female development → limited ovarian functioning and oestrogen

Interpreting unfamiliar scenarios

A question may provide characteristics without naming the chromosome pattern.

Look for combinations such as:

Scenario clue	Likely condition
XYXYXY, androgens present, typically female external characteristics	AIS
Male, tall, small testes, reduced testosterone	Klinefelter’s syndrome
Female, shorter stature, underdeveloped ovaries, low oestrogen	Turner syndrome

Do not identify a condition from one characteristic alone. For example, being tall does not demonstrate Klinefelter’s syndrome without relevant chromosomal or developmental information.

Hints from the Examiner Reports 💡

The supplied examiner reports pre-date examination of AIS under the revised specification, so no direct AIS-specific performance guidance was identified.

Examiner hint: Use accurate chromosome notation. AQA mark schemes identify XXYXXYXXY with Klinefelter’s syndrome and XOXOXO, also written X0X0X0, with Turner syndrome. Reversing these patterns would undermine the entire explanation.

Examiner hint: Develop the biological process. Earlier AQA questions rewarded answers that linked chromosome pattern, the SRY gene, testes and hormone production rather than simply listing XXXXXX and XYXYXY.

Examiner hint: Do not drift into an unrelated essay about aggression or gender roles. In the 2022 chromosome-and-hormone question, knowledge was generally strong, but some students’ discussion focused on testosterone and aggression without shaping the material to the question.

Examiner hint: Use specialist terminology carefully. Useful terms include SRY, androgen, hormone sensitivity, XXYXXYXXY, X0X0X0, testes and ovaries.

Examiner hint: When discussing AIS, separate the stages clearly. The person can have XYXYXY chromosomes, develop testes and produce androgens while still not showing typical male external development because the tissues are insensitive.

Examiner hint: For a “describe” question, provide relevant characteristics and the biological mechanism. Do not add a lengthy evaluation unless the command word requires it.

Examiner hint: For an application question, use the details provided. Identify the chromosome pattern or hormonal clue, name the condition and explain the developmental outcome.

Examiner hint: Avoid unsupported assumptions about identity. The conditions concern diversity in biological development and do not tell you how a person identifies.

Common Mistakes ⚠️

Mistake: Saying AIS is caused by a lack of testosterone

Why this is incorrect:

A person with AIS may produce androgens. The central issue is that body tissues do not respond typically to them.

How to improve:

Distinguish hormone production from hormone sensitivity.

Mistake: Saying a person with AIS has an XXXXXX chromosome pattern

Why this is incorrect:

AIS usually involves an XYXYXY chromosome pattern.

How to improve:

Remember:

AIS = XYXYXY, but insensitive to androgens.

Mistake: Assuming XYXYXY always produces typically male external characteristics

Why this is incorrect:

Complete AIS shows that hormone receptors and tissue sensitivity are also required.

How to improve:

Explain the whole biological pathway rather than using chromosomes alone.

Mistake: Saying XXYXXYXXY produces female development

Why this is incorrect:

The YYY chromosome normally contains SRY, so a person with Klinefelter’s syndrome develops as male.

How to improve:

Look for the presence of the YYY chromosome before counting the number of XXX chromosomes.

Mistake: Confusing Klinefelter’s syndrome with Turner syndrome

Why this is incorrect:

Klinefelter’s syndrome involves an additional XXX, while Turner syndrome involves a missing sex chromosome.

How to improve:

Use:

Klinefelter’s = XXYXXYXXY.
Turner = X0X0X0.

Mistake: Saying Turner syndrome means no XXX chromosomes are present

Why this is incorrect:

A person with Turner syndrome has one XXX chromosome.

How to improve:

Explain that the second sex chromosome is absent.

Mistake: Saying Turner syndrome produces male development

Why this is incorrect:

There is no YYY chromosome or SRY gene, so male development is not initiated.

How to improve:

State that Turner syndrome is associated with female development and affected ovarian functioning.

Mistake: Treating every associated characteristic as universal

Why this is incorrect:

Individuals differ in the characteristics they experience and their degree of severity.

How to improve:

Use phrases such as:

“May include”.
“Is associated with”.
“Can affect”.

Mistake: Describing DSD as a gender identity

Why this is incorrect:

DSD concerns biological development. Gender identity concerns a person’s experience and understanding of their gender.

How to improve:

Keep biological sex and gender identity conceptually distinct.

Mistake: Listing characteristics without explaining their significance

Why this is incorrect:

The learning objective asks how the conditions contribute to understanding biological sex.

How to improve:

For each condition, add a sentence explaining what it demonstrates about chromosomes, hormones or hormone sensitivity.

Exam-Style Questions ✍️

Questions

1. Name the three examples of diversity in sex development included in the AQA specification.[3 marks]

2. What chromosome pattern is associated with each of the following?

a) Klinefelter’s syndromeb) Turner syndrome[2 marks]

3. Outline androgen insensitivity syndrome.[4 marks]

4. Explain one difference between androgen insensitivity syndrome and Klinefelter’s syndrome.[4 marks]

5. Genetic testing shows that Alex has an XYXYXY chromosome pattern. Alex has internal testes that produce androgens but has typically female external sexual characteristics.

Explain Alex’s development.[4 marks]

6. Jamie has an XXYXXYXXY chromosome pattern, small testes and lower than typical testosterone production.

Use your knowledge of diversity in sex development to explain Jamie’s characteristics.[4 marks]

7. Morgan has one XXX chromosome and no second sex chromosome. Morgan has developed as female but has underdeveloped ovaries and produces relatively little oestrogen.

Explain Morgan’s development.[4 marks]

8. Explain two ways in which diversity in sex development contributes to understanding biological sex.[6 marks]

9. Discuss what androgen insensitivity syndrome, Klinefelter’s syndrome and Turner syndrome tell psychologists about biological sex development.[8 marks]

Answers and Mark Scheme

Question 1

Award one mark for each:

Androgen insensitivity syndrome.
Klinefelter’s syndrome.
Turner syndrome.

Question 2

Award one mark for each:

a) Klinefelter’s syndrome: XXYXXYXXYb) Turner syndrome: X0X0X0 or XOXOXO

Question 3

Award up to four marks:

AIS usually occurs in a person with an XYXYXY chromosome pattern.
The SRY gene normally initiates testicular development.
The testes produce androgens.
Body tissues respond partly or not at all to the androgens.
In complete AIS, typically male external development does not occur and external development is typically female.

Question 4

Award up to four marks for a clear comparison.

Possible content:

AIS usually involves an XYXYXY chromosome pattern, whereas Klinefelter’s syndrome involves XXYXXYXXY.
In AIS, testes may produce androgens but tissues cannot respond typically.
In Klinefelter’s syndrome, the person develops as male but testicular functioning and testosterone production may be reduced.
AIS primarily demonstrates altered hormone sensitivity, while Klinefelter’s syndrome involves an additional chromosome affecting hormone production and development.

Question 5

Award up to four marks:

Alex’s XYXYXY pattern normally includes the SRY gene.
SRY initiated the development of testes.
The testes produced androgens.
Alex’s tissues were insensitive to the androgens.
Typical male external sexual development therefore did not occur.
The development is consistent with androgen insensitivity syndrome.

Question 6

Award up to four marks:

Jamie’s XXYXXYXXY pattern is associated with Klinefelter’s syndrome.
The YYY chromosome normally contains the SRY gene.
SRY initiates the development of testes and male sexual development.
The additional XXX can affect testicular functioning.
This may explain the small testes and reduced testosterone production.

Question 7

Award up to four marks:

Morgan’s chromosome pattern is X0X0X0.
This is associated with Turner syndrome.
There is no YYY chromosome or SRY gene, so male development is not initiated.
The person therefore develops as female.
The missing second sex chromosome affects ovarian development.
Reduced ovarian functioning explains the lower oestrogen production.

Question 8

Award up to three marks for each developed point.

Possible answers include:

AIS demonstrates that chromosomes alone do not determine external sexual development. An XYXYXY individual may develop typically female external characteristics if tissues cannot respond to androgens.
Klinefelter’s syndrome shows the importance of the YYY chromosome and SRY because a person develops as male despite having two XXX chromosomes.
Turner syndrome shows that one XXX chromosome can support female development, although the second sex chromosome is important for typical ovarian functioning.
The conditions show that chromosomes, gonads, hormones and hormone receptors interact.
They demonstrate that biological sex characteristics show greater variation than a strict XXXXXX/XYXYXY rule suggests.

Question 9

A strong answer should include:

Knowledge and understanding

The meaning of diversity in sex development.
XYXYXY chromosomes in AIS.
Testicular and androgen production in AIS.
Reduced or absent response to androgens.
Female external development in complete AIS.
XXYXXYXXY chromosomes in Klinefelter’s syndrome.
Male development due to the YYY chromosome and SRY.
Reduced testicular functioning or testosterone.
X0X0X0 chromosomes in Turner syndrome.
Female development in the absence of SRY.
Limited ovarian functioning or oestrogen production.

Discussion and explanation

AIS shows that hormone sensitivity matters as well as hormone production.
Klinefelter’s syndrome demonstrates the influence of the YYY chromosome even when two XXX chromosomes are present.
Turner syndrome shows that female development can occur with one XXX, although the second chromosome affects reproductive development.
Biological sex is multidimensional.
Chromosomes, genes, gonads, hormones, receptors and anatomy interact.
A chromosome-only account is biologically reductionist.
Typical XXXXXX and XYXYXY pathways remain common, but they do not describe every individual.
Biological sex characteristics should not be confused with gender identity.
Language and research concerning DSD should be handled sensitively.

Higher-level answers will compare the three conditions directly and explain what each one reveals about the biological pathway from chromosomes to sexual development.