Lecture 6: Sex Determination and Dosage Compensation

Question 1

Sex-limited inheritance

Answer 1

• Autosomal genes affect trait
• Trait can be only expressed in one sex
  E.g: cock feathering in chickens

Question 2

Sex-influenced inheritance

Answer 2

• Autosomal genes affect trait
• Trait is expressed to a lesser degree in one sex
  E.g: baldness

Question 3

Dosage compensation

Answer 3

• The different methods different species undergo to overcome the fact that females have twice as many X chromosomes and genes as males so the same amount of X chromosomal genes is activated in both sexes
• In humans, females inactivate one X, but which X is inactivated can depend on the tissue, creating a mosaic. This X inactivation causes a “Barr body”
• X inactivation follow the N-1 rule where N is the number of X chromosomes you have, so you could be female and have three X chromosomes and two will be inactivated, or you could be male and have two X chromosomes and one will be inactivated.