Summary: Chapter 3 -Sex Differences In Behavior: Sex Determination And Differentiation

Read the summary and the most important questions on Chapter 3 -Sex differences in behavior: sex determination and differentiation

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• What is sex determination?

  When the ovum is fertilized by a sperm containing either an X or a Y chromosome.

• What are the main differences between boys and girls?

  1. Girls have better verbal abilities and they engage more in nursing behavior.
  2. Boys are more likely to suffer from dyslexia, they are better at visual and spatial tasks, they are more aggressive and they engage more in rough-and-tumble play. 

• What is the Turner syndrome?

  • Characterized by a congenital (aangeboren) lack of, or damage to, the 2nd X or the Y chromosome (=XO). 
    
  • They are born as girls but the gonads don't develop completely because the ovaries don't produce steroid hormones.
    
  • The girls must be treated with sex steroid hormones to induce puberty.

• What is androgen insensitivity syndrome (AIS) and what 2 types are there?

  • Complete androgen insensitivity syndrome (CAIS). Genetic XY males with CAIS don't have functional androgen receptors and their testes produce MIH. These males look like females but have a 'blind' vagina and they are infertile.
  • Partial androgen insensitivity syndrome (PAIS). Partially non-functional androgen receptors. XY individuals have partially, but not fully, masculinized external genitalia. 

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• Explain gender identity and sexual orientation.

  • Gender identity: reflects the sex, or gender, that individuals feel themselves to be.
    
  • Sexual orientation: straight, gay, bi, etc.

• What is parthenogenesis? Explain how it works and its disadvantages.

  Parthenogenesis is the process of asexual reproduction in vertebrate animals.
  

  • There is only one sex: female.
    
  • They produce genetically identical eggs that develop into female offspring that are all 100% genetically identical to their mother. 

  
  Disadvantages:
  

  • They provide little variation on which evolution can act.
  • Pathogens may become specialized to exploit a single genotype. 

• Explain the organizational/activational hypothesis in short.

  It is a hypothesis on how hormones guide behavior that suggests that behavioral sex differences result from:
  

  1. Differential exposure to hormones that act early in development to organize the neural circuit underlying sexually dimorphic behavior.
  2. Differential exposure to sex steroid hormones later in life that activate the neural circuit previously organized.  
     

• What is the germinal ridge?

  Each individual embryonic mammal (XX or XY), has a thickened ridge of tissue on the ventromedial surface of each protokidney called the germinal ridge. It will develop in either the ovary or the testis.

• What is the SRY gene?

  SRY gene is the sex determining region of the Y gene and it determines male or female sex .
  

  • It encodes the testes determination factor. When protein products of this gene are produced, the middle of the germinal ridge develops and a testis forms.
  • If SRY gene is not expressed, the outer part of the germinal ridge develops and an ovary is formed. 
    

• What are the Müllerian and Wolffian duct systems?

  • Müllerian duct system develops into the female accessory sex organs: the fallopian tubes, uterus and cervix.
    
  • Wolffian duct system develops into the male accessory sex organs, which connect the testes to the outside environment through the penis. Later-developing components include seminal vesicles and vas deferens.