PSY/340 Biological Psychology
Instructor: Rebecca Wilson
June 12, 2010
Biological Foundations of Adult Sexual Development
How humans develop prenatally
Humans start out as a cell that is formed from the mother’s egg and the father’s sperm. The egg and sperm carry 23 single chromosomes each and when fertilization takes place the 23 chromosomes then become paired. “All genetically normal humans, regardless of their sex, share 22 pairs of chromosomes and only one pair is different” (Wickens, 2005, p. 204). The different pair is the sex chromosomes (X and Y). A female is (X, X) and a male is (X, Y). As the cell develops into a fetus there are several hormones involved. These hormones continue to work throughout the human body as we grow from an infant into an adult. The hormones effect our sexual development and sexuality. Affects of hormones on a fetus
As the fetus grows it will physically appear gender neutral, but at about 6 week gestation the Y chromosome, if present, will release a chemical called testis-determining factor which causes the internal male sex organs to start forming. If the Y chromosome is not present then this chemical is not released and the internal female sex organs will start to form. The male hormones that cause the external organs to develop are called androgens, without these we would all have female external sex organs (Spencer A. Rathus, 2005). Some of the different androgens are: testosterone, dihydrotestosterone (DHT), and Mullerian inhibiting substance (MIS). If any of these hormones are missing or do not release the amount they are suppose to at the time they are suppose to the fetus will have genetic sexual disorders such as: Klinefelter syndrome, congenital adrenal hyperplasia, pseudo-hermaphrodite, and testicular feminisation syndrome (Wickens, 2005). The lack of these hormones not only affects the physical appearance of the fetus, but also the...