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

Question 1

h

Answer 1

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

Question 2

h

Answer 2

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

Question 3

h

Answer 3

Criteria for sex:

• chromosomal
• gonadic (ovaries, testes)
• passport
• hormonal
• anatomic
• psycho-emotional
• social

Question 4

h

Answer 4

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

Question 5

g

Answer 5

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