23. Sex and sexual traits. Determination and differentiation of the sex. Flashcards

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Secondary sex characteristics - these changes begin at puberty

  • differences in sexual behaviour
  • body hair distribution
  • male - facial hair, deepening of voice
  • female - growth of breasts

Androgens control the development of secondary sex characteristics in males

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2
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Determination of sex - factors that push development in male or female direction:

  • X and Y chromosomes are sex defining
  • under the influence of inherited or external factors
  • Programmed determination: before fertilisation, during egg production
  • Epigamic - through environmental conditions (temperature, moisture) e.g. turtles
  • Singamic - chromosomally determined, due to heterochromosome
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3
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Criteria for sex:

  • chromosomal
  • gonadic (ovaries, testes)
  • passport
  • hormonal
  • anatomic
  • psycho-emotional
  • social
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4
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At 7th week of development - gonad differentiation, the presence of SRY gene in the Y chromosome encodes a protein that causes expression of the genes for testicular development.

Without SRY gene - gonads differentiate into ovaries Gp box gene - ovaries testosterone is produced until differentiation finishes and stops with puberty oestrogen is only produced at puberty

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5
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Hypothalamus, pituitary gland and adrenal glands -produce hormones Sex determining hormones are secreted by the ovaries and testes Leydig cells produce testosterone

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