2 Gender- chromosomes, hormones and atypical chromosomal patterns

Name the typical sex chromosome patterns in males and females.

Females- XX

Males- XY

Name the atypical chromosome patterns that can happen in males and females.

Males- XXY (Klinefelter’s)

Females- XO (Turner’s)

Name the hormones produced by the testes and ovaries.

Testosterone, oestrogen and progesterone.

What is the definition of a chromosome?

Found in the nucleus of living cells carrying information in the form of genes; the 23rd pair of chromosomes determines biological sex.

What is the definition of a hormone?

A chemical substance circulated in the blood that controls and regulates the activity of certain cells or organs.

What is testosterone?

A hormone from the androgen group that is produced mainly in the male testes (and in smaller amounts in the female ovaries), it is associated with aggression.

What is oestrogen?

The primary female hormone, playing an important role in the menstrual cycle and reproductive system. 

What is oxytocin?

A hormone which causes contraction of the uterus during labour and stimulates lactation.

What study provides evidence for a link between testosterone and aggressive behaviour?

Poll et al. showed that female rats who had been injected with testosterone became more physically and sexually aggressive.

Explain Dabbs study.

He found that in prison populations, the offenders with the highest levels of testosterone were more likely to have committed violent or sexually motivated crimes. 

Explain Van Goozen et al’s study.

She studied transgender individuals who were undergoing hormone treatment and being injected with hormones of the opposite sex. Transgender women (male-to-female) showed decreases in aggression and visuo-spatial skills whilst transgender men (female-to-male) showed the opposite. This research seems to suggest that sex hormones do exert some influence on gender-related behaviours.

What is the strength of the role of hormones and chromosomes on gender?

• Evidence in support → Reimer, Dabbs and Van Goozen

What are the limitations of the role of hormones and chromosomes on gender?

• Contradictory evidence → Tricker- 43 males were given either a weekly injection of testosterone or a placebo, there were no significant differences in aggression between the two groups. →  Slabbekoorn et al.- demonstrated that sex hormones had no consistent effect on gender-related behaviour. 

• Many of the studies were conducted on animals which limits their generalisability. 

• Objections to pre-menstrual syndrome- some people believe it is a social construct and not biological.

• Overemphasis on nature- social learning theory points to the importance of social context in the learning of our gender identity and gender role. 

• Oversimplifies a complex concept

Define atypical sex chromosome patterns.

Any sex chromosome pattern that deviates from the usual XX/XY formation and which tends to be associated with a distinct pattern of physical and psychological symptoms.

What is Klinefelter’s syndrome?

An atypical chromosome pattern, which affects between 1 in 500 and 1 in 1000 people, people with this condition are biological males, with the anatomical appearance of a male but have an additional X chromosome.

What is the chromosomal pattern of someone with Klinefelter’s syndrome?

XXY

What are the physical characteristics of someone with Klinefelter’s syndrome?

• Reduced body hair

• Breast development

• Long, gangly limbs

• Underdeveloped genitals

• Problems with co-ordination and general clumsiness

• More susceptible to health problems commonly found in females, such as breast cancer

What are the psychological characteristics of someone with Klinefelter’s syndrome?

• Poorly developed language skills

• Poorly developed reading ability

• Tend to be passive, shy and lack interest in sexual activity

• Tend not to respond well to stressful situations

• Exhibit problems with executive function such as memory and problem solving