The Biological The Biological explanation of explanation of

gendergender

Lesson ObjectivesLesson Objectives

By the end of this lesson you willBy the end of this lesson you will

understand:understand:

1.1. Typical sex chromosome patternsTypical sex chromosome patterns

2.2. Atypical sex chromosome patternsAtypical sex chromosome patterns

3.3. Dabbs et al (1995)Dabbs et al (1995)

Biological explanationsBiological explanations

Biopsychologists assume that all Biopsychologists assume that all gender differences are totally gender differences are totally

attributed to chromosomal attributed to chromosomal differences, differences in brain differences, differences in brain

structure & function and differences structure & function and differences in hormonal activity.in hormonal activity.

Biological explanationsBiological explanations• The normal humanThe normal humanbody contains 23 pairs body contains 23 pairs of chromosomes. of chromosomes.

• Each pair of Each pair of chromosomes chromosomes carries genes that carries genes that control different control different characteristics. characteristics.

• Biological sex is Biological sex is determined by the determined by the 23rd pair. So females 23rd pair. So females have the have the genotype genotype

XX XX and males the and males the genotype XY. genotype XY.

Atypical sex-chromosomesAtypical sex-chromosomes

• Any combination of sex Any combination of sex chromosomes other than XX or XY is chromosomes other than XX or XY is seen as atypical.seen as atypical.

• Klinefelter’s and Turner’s syndrome Klinefelter’s and Turner’s syndrome are examples of conditions which are examples of conditions which result from atypical sex chromosome result from atypical sex chromosome conditions.conditions.

Klinefelter SyndromeKlinefelter Syndrome

Turner syndromeTurner syndrome

Atypcial ChromosomesAtypcial ChromosomesKlinefelter Syndrome Klinefelter Syndrome

(XXY)(XXY)Caused by the presence of an Caused by the presence of an extra X chromosomeextra X chromosome

Biological male with a physical Biological male with a physical appearance of maleappearance of male

Affects between 1 in 500 and 1 in Affects between 1 in 500 and 1 in 1000 males1000 males

Psychological effects: poor Psychological effects: poor language skills – which affects language skills – which affects reading ability, passive reading ability, passive temperamenttemperament

Physical effects: less body hair Physical effects: less body hair than normal male, than normal male, underdeveloped genitals, long underdeveloped genitals, long legs in relation to torso, infertilelegs in relation to torso, infertile

Turner Syndrome (XO)Turner Syndrome (XO)Caused by the absence of an X Caused by the absence of an X chromosomechromosome

Biological female with the female Biological female with the female external appearanceexternal appearance

Affects 1 in 2500Affects 1 in 2500

Psychological effects; higher than Psychological effects; higher than average reading ability; lower average reading ability; lower than average spatial ability, visual than average spatial ability, visual memory and mathematical skills; memory and mathematical skills; difficulty is social adjustmentdifficulty is social adjustment

Physical effects; ovaries fail to Physical effects; ovaries fail to develop, short squat body with develop, short squat body with webbed neck webbed neck

Atypical ChromosomesAtypical Chromosomes

• What does studying people with What does studying people with atypical sex chromosome patterns atypical sex chromosome patterns allow us to conclude what about allow us to conclude what about gender?gender?

Atypical ChromosomesAtypical Chromosomes

It provides evidence that our biological makeup It provides evidence that our biological makeup is responsible for gender-related behaviour.is responsible for gender-related behaviour.

For example, by comparing someone with For example, by comparing someone with typical chromosomes to someone with typical chromosomes to someone with

atypical chromosomes you can make clear atypical chromosomes you can make clear comparisons what aspects of their comparisons what aspects of their behaviour have a genetic cause.behaviour have a genetic cause.

Studies to support:Studies to support:Imperato mc Ginley et al (1979)Imperato mc Ginley et al (1979)

Money and Erhardt (1972)Money and Erhardt (1972)

Chromosomes Chromosomes

Q.Q. Give the typical sex chromosome Give the typical sex chromosome pattern for the following:pattern for the following:

a malea male

a female a female

(2 marks)(2 marks)

Exam questionsExam questions

Q. Identify one atypical sex Q. Identify one atypical sex chromosome pattern and outline how chromosome pattern and outline how it might affect an individual. it might affect an individual.

(3 marks)(3 marks)

Past papersPast papers

Victoria is five years old and she is different from other girls of her Victoria is five years old and she is different from other girls of her age. age.

She is smaller in height and has a webbed neck. At school, her She is smaller in height and has a webbed neck. At school, her teachers have commented that she has good verbal skills but her teachers have commented that she has good verbal skills but her mathematical skills are poor. Medical tests have revealed that Victoria mathematical skills are poor. Medical tests have revealed that Victoria has a sex chromosome pattern XO.has a sex chromosome pattern XO.

Q.Q. Name the atypical sex chromosome syndrome described above. Name the atypical sex chromosome syndrome described above. (1 mark)(1 mark)

Q.Q. Identify how Victoria’s sex chromosome pattern differs from Identify how Victoria’s sex chromosome pattern differs from that of most girls. that of most girls. (1 mark)(1 mark)

Q.Q. Explain how studying people like Victoria can contribute to our Explain how studying people like Victoria can contribute to our understanding Of gender. understanding Of gender. (2 marks)(2 marks)

SummarySummary

• What three things have you learned What three things have you learned today….today….

Q Name one sex hormone and give an Q Name one sex hormone and give an example of how this hormone might example of how this hormone might affect a affect a person’s behaviour.person’s behaviour. (2 marks) (2 marks)

Discuss biological explanations of gender Discuss biological explanations of gender development. Refer to at least one study development. Refer to at least one study in your answer.in your answer. (10 marks) (10 marks)