the role of chromosomes and hormones

  • The role of chromosomes
  • Male development
  • female development
  • the role of hormones
  • everyone has 23 sets of chromosomes - 1 half from mother & 1 half from father
  • chromosomes carry our DNA which is made up of our genes (which determines our characteristics)
  • the 23rd pair are what determines your sex - specifically inherited from your father
  • in the first 6-8 weeks all foetuses have the same undeveloped sex organs
  • the original system can develop into both male/female sex organs
  • it is the presence/absence of a single gene (the Sex Determining Region Y or SRY gene) which will dictate the future development of the foetus as male/female.
  • every foetus develops as a female unless instructed otherwise
  • the Y chromosome contains instructions for the body to produce androgens (male sex hormones)
  • these cause the embryo to develop along the 'male path'
  • SRY gene produce a protein: Testes Determining Factor (TDF)
  • TDF influences the development of the gonads, they become testes
  • the testes produce androgens such as testosterone
  • testosterone triggers the development of external male organs, i.e., penis
  • the absence of male hormone will result in the development of the Mullerian system into female sex organs
  • most gender development comes from the influence of hormones on prenatal:
  • brain development
  • development of reproductive organs
  • puberty: pituitary glands (triggered by hypothalamus) causes gonads to produce a bursts of hormonal activity, which triggers development of secondary sexual characteristics
  • once testes and ovaries develop they begin to release their own sex hormones:
  • male hormones are known as androgens - the most widely known of which is testosterone
  • females hormones are mostly oestrogen & oxytocin
  • Testosterone
  • male hormone, but is present in small quantities in women.
  • if genetic male produce no/little testosterone during foetal development then no male sex organs appear. if genetic female produces high levels of testosterone during foetal development, male sex organs may appear
  • high levels of testosterone (evolution) are also linked to aggression because it's adaptive.
  • aggression towards rivals allows males to compete for opportunity to mate with a fertile female.
  • Oestrogen
  • determines female sexual characteristics and menstruation.
  • alongside physical changes, oestrogen may make women more emotional and irritable during their menstrual cycle
  • in extreme case, PMS has be used successfully as a defence in cases of shoplifting & even murder
  • referred to as Premenstrual tension (PMT) or Premenstrual syndrome (PMS).
  • Oxytocin
  • Women typically produce more oxytocin that men, particularly as a result of giving birth
  • hormone stimulates lactation, making it possible for mothers to breastfeed their children.
  • it also reduces the stress hormone cortisol and facilitates bonding, for this reason it has been referred to as the 'love hormone'.
  • oxytocin released in huge amounts during labour and after childbirth & makes new mothers feel 'in love' with their babies
  • Evaluation

click to edit

click to edit

click to edit