biological sex (cognito)

Biological sex:

describes whether an individual is male, female, or intersex, based on physical and genetic characteristics

how is gender different?

relates to social and cultural roles

how many pairs of chromosomes do humans have?

23

what pair of chromosomes determine biological sex?

23rd

Key characteristics of sex chromosomes:

• Females typically have XX sex chromosomes, meaning all eggs (ova) carry an X chromosome.

• Males typically have XY sex chromosomes, so sperm can carry either an X or a Y chromosome.

• The Y chromosome triggers male development; without it, female development occurs.

• Fertilisation by an X-carrying sperm results in an XX (female) offspring, while a Y-carrying sperm leads to XY (male) offspring. This process happens randomly.

• Gametes like sperm and ova each contain only one sex chromosome.

what do hormones play a key part in?

shaping physical development and sexual characteristics from the foetal stage onwards

what are androgens (testosterone) and oestrogens?

the primary hormones influencing sex development. both exist in males and females, but levels differ significantly: males produce more testosterone and females produce more oestrogen

what happens in early foetal development?

reproductive structures are initially identical in both sexes

what does a specific gene on the Y chromosome prompt?

the development of male genitalia and testosterone production. in its absence, female genitalia form and testosterone levels remain low

what is the specific gene on the Y chromosome?

The specific gene on the Y chromosome that triggers male development is the SRY (Sex-determining Region Y) gene. It causes the foetal gonads to develop into testes, which then begin producing testosterone.

not all individuals follow the typical XX or XY patterns…

some are born with chromosomal or hormonal variations that affect physical traits and fertility

Klinefelter's syndrome

Individuals have XXY sex chromosomes (an extra X chromosome in males).

Common characteristics:

• Sterility

• Reduced muscle mass

• Less facial or body hair

Turner's syndrome

Individuals have a single complete X chromosome, with the second X partially or fully absent (in females).

Typical features:

• Shorter stature

• Non-functioning ovaries leading to sterility

• Atypical puberty progression

Androgen insensitivity syndrome (AIS)

The foetus has XY chromosomes but shows reduced or no response to testosterone, altering typical male development.

Types of AIS:

• Partial AIS (PAIS) - Partial testosterone response, resulting in ambiguous or underdeveloped genitalia that may appear female or male.

• Complete AIS (CAIS) - No response to testosterone, leading to female external genitalia.

Individuals with AIS lack a uterus and ovaries, and puberty does not follow the standard pattern. These variations can influence how individuals are raised in terms of gender.

Students often confuse which atypical chromosome pattern affects which sex:

Remember the genetic trigger:

• Klinefelter's syndrome (XXY) - Affects males, because the presence of a Y chromosome triggers male development despite the extra X.

• Turner's syndrome - Affects females, because there is no Y chromosome present to prompt male development.

what does biological sex exist on a spectrum beyond?

beyond the traditional male female binary, encompassing intersex variations that challenge simplistic categorisations

what can viewing sex as strictly binary lead to?

stigma, discrimination, and mental health challenges for those who don’t fit the categories

what does recognising diversity promote?

inclusivity and reduces harm, highlighting the need for awareness in psychological and social contexts

key terms:

Biological sexAn individual's physical and genetic status as male, female, or intersex, typically determined by chromosomes and anatomy.

IntersexA general term for variations in sex characteristics that do not fit typical binary notions of male or female bodies.

AndrogensA group of hormones, including testosterone, that play a key role in male traits and reproductive activity.

OestrogensA group of hormones primarily responsible for the development and regulation of the female reproductive system.

Klinefelter's syndromeA chromosomal condition where a male is born with an extra X chromosome.

Turner's syndromeA chromosomal condition where a female is born with only one complete X chromosome.

Androgen insensitivity syndrome (AIS)A condition where an individual with XY chromosomes does not respond fully to testosterone, altering typical male development.

Testosterone 

Known as an androgen (male sex hormone). Biological males have 10 times the level of biological females and it is released when the SRY gene is detected on the Y chromosome. Production of testosterone during 7th week of gestation leads to the development of male sex organs (testes & penis). Levels in biological males rise during puberty and affect physical traits such as body and facial hair, muscle mass and height. In biological females, most testosterone in the ovaries is converted to oestrogen.

Oestrogen   

Although produced in both the testes and ovaries, oestrogen levels are much higher in biological females. Before birth, oestrogen promotes the development of the endocrine system in both males and females. Oestrogen Influences the development of secondary sex characteristics such as breast development and the menstrual cycle (ovulation). In biological males, it affects the development of male sex organs, erectile function and sperm cell production.

Oxytocin  

Known as the ‘cuddle’ or ‘love’ hormone, oxytocin is produced by biological males and females. Levels are higher in biological females and higher again during and after childbirth. This hormone prepares the female body for childbirth and lactation to aid breast feeding. It also reduces stress hormones such as cortisol in both biological males and females.