Role of chromosomes and hormones Flashcards
When are chromosomal patterns determined and on which pair of chromosomes
The chromosomal pattern of a male and female is determined at fertilisation and the genetic information on the 23rd pair of chromosomes determines biological sex.
What are hormones
Chemical messengers that are released into the bloodstream from glands that control and regulate the activity of certain cells and organs.
State the typical chromosomal structure for females and males
XX for females and XY for males.
State the 3 main hormones involved in sex and gender
Testosterone, oestrogen and oxytocin.
Explain how biological sex is determined
Chromosomes determine a baby’s sex at fertilisation – all normal egg cells carry an X chromosome, and sperm carry an X or Y chromosome. If the egg is fertilised by a Y chromosome carrying sperm, the child will be male and if the sperm carries an X chromosome, then the child will be female.
Explain the role of hormones prenatally
An individual’s chromosomal pattern alters the hormones released pre and postnatally; the hormones released prenatally influence which internal and external genitalia the foetus will develop. All embryos begin with gonads which, depending upon the hormones released, either turn into testes or ovaries; gonadal differentiation occurs around six weeks after fertilisation.
Describe how the production of testosterone determines sex
Oestrogen is produced by both XX and XY babies in the womb.
The Y chromosome carries the sex-determining region (SRY) gene which inhibits the release of oestrogen approximately 2 months after conception and initiates androgen (testosterone) production which triggers the development of male phenotypes and characteristics of a male. Testosterone also affects the development of secondary sexual characteristics during puberty which are triggered by sexual organ maturity.
Describe how the production of oestrogen determines sex
Oestrogen is produced by both XX and XY babies in the womb.
If there is no Y chromosome, then oestrogen production continues and initiates the development of female phenotypes and characteristics of a female. Oestrogen plays a critical role postnatally as it directs the menstrual cycle and triggers secondary sexual characteristic development.
What is oxytocin?
A hormone produced in the hypothalamus which controls key aspects of the reproductive system (testosterone inhibits its action in males) especially labour and breast-feeding in mothers, as well as nurturing / bonding behaviour in both sexes.
State the case study which supports the biological explanation for gender
David Reimer.
What are chromosomes?
Found in the nucleus of living cells which carry all the genetic information (DNA) for an organism. Humans have 46 arranged into 23 pairs.
What is testosterone?
A male hormone produced in the testes that controls the development of male sex organs prenatally and stimulates the development of secondary characteristics during puberty.
What is oestrogen?
A female hormone produced by the ovaries which determines sex organs prenatally and stimulates the development of secondary sex characteristics during puberty. Also directs the menstrual cycle.
Outline the case study of David Reimer
David Reimer was born as the elder of identical twin boys. When the twins were 7 months old, they were referred for circumcision to fix a urinary problem. Tragically, the operation on David was botched and David’s penis was burned beyond surgical repair. David’s parents sought advice from Dr. John Money, a psychologist who was developing a reputation as a pioneer in the field of sexual development and gender identity. Money and his team persuaded the baby’s parents that sex reassignment surgery would be in Reimer’s best interest. At the age of 22 months, David underwent the procedure in which his testes were surgically removed, and a rudimentary vulva was constructed by genital plastic surgery. David was reassigned to be raised as female. Over the next 10 years the twins visited Money regularly because their case provided a unique natural experiment, a normal XY male raised as a female with an identical twin brother as a control. By the age of 13 years, Reimer was experiencing suicidal depression and he told his parents he would take his own life if they made him see Money again. Finally at 14 Reimer’s parents told him the truth about his sex reassignment, following advice from Reimer’s endocrinologist and psychiatrist. Having been informed of his past by his father, Reimer decided to assume a male gender identity, calling himself David. He underwent treatment to reverse the reassignment, including testosterone injections, a double mastectomy, and phalloplasty operations.
3 Strengths for the role of chromosomes and hormones (1 COUNTER)
Support from individuals raised as a different gender to their sex:
David Reimer
Reiner and Gearhart (2004) studied 16 genetic males born with almost no penis. Two were raised as males and remained males; the remaining 14 were raised as females. 8 of these females reassigned themselves as males by the age of 16.
Research support for the role of testosterone:
The link between increased testosterone and sexual behaviour in mature males was seen in a study by Wang et al. (2000). Male hypogonadism is a condition caused by a man’s testes failing to produce normal levels of the male sex hormone. 227 hypogonadal men were given testosterone therapy for 180 days. Testosterone replacement improved sexual function, libido and mood, and significant increases in muscle strength were observed within the sample. This study shows that testosterone exerts a powerful and direct influence on male sexual arousal, as well as physical development, in adulthood.
COUNTER - however, other evidence on the effect of testosterone is less convincing. In a double-blind, placebo study, O’Connor et al. (2004) increased testosterone levels in healthy young men. There was no significant increase in aggression and ager, as well as the interactional (i.e. frequency of sexual intercourse) or non-interactional (i.e. sex drive) components of sexual behaviour in participants. This suggests that additional testosterone may have no effect on sexual or aggressive behaviour.
Real-life application:
Research into the role hormones in sex and gender has led to significant beneficial practical applications.
For example, administering oxytocin has proved beneficial during childbirth as it reduces haemorrhaging, decreasing mortality rates in mothers and infants. Oxytocin has also proved helpful in instigating labour and maintaining labour and the secretion of milk so mothers can breastfeed. Testosterone has proven useful for men with problems attaining and maintaining erections or with low libido. It has also proved useful in increasing libido in women who are post-menopausal or have had a hysterectomy. Whilst oestrogen supplements offer increased protection against the risk of strokes and protection against osteoporosis in post-menopausal women.
2 Limitations for the role of chromosomes and hormones
Reductionist view:
Ignores and underestimates alternative explanations for gender development.
The cognitive approach would draw attention to the influence that changing thought processes, such as schemas, have on gender development. Specifically, they would suggest that children look to the gendered behaviour of their in-group to make sense of the world and their place in it.
Furthermore, the biological account ignores the vital role of social factors in gender-related behaviour. Hofstede et al. (2010) claim that gender roles around the world are much more a consequence of social norms than biology. Countries that place individual competition and independence above the needs of the community are more masculine in their outlook. Consequently, traditional masculine traits will be more highly valued within these societies.
These alternative explanations challenge the biological explanations of gender behaviour which therefore suggest that gender is far more complex than its biological influences alone, and other factors may be more important in shaping gender behaviour and attitudes
Overemphasis on nature:
Evidence has shown that societal and cultural practices play an equally critical role in gender development. Imperato-McGinley et al. (1974) studied 4 children in the Batista family who were born with external female genetalia and raised as females. When they hit puberty the large increase in testosterone caused their male genetalia to appear. The “girls” accepted their new male identity without any difficulty. The ease of transition from male to female was due to acceptance of fluidity of gender within their community. This suggests that factors associated with nature can shape gender identity.
