Sex Determination In Mammals

Sex Determination in Mammals

Central Idea

• The process by which an individual's sex is determined in mammals

Main Branches

1. Genetic Sex Determination
2. Environmental Sex Determination

Genetic Sex Determination

• The sex of an individual is determined by the presence or absence of certain sex chromosomes
• Two main types of sex chromosomes:
  • XX: Female
  • XY: Male
• Other sex chromosome systems:
  • X0: Female (only one X chromosome)
  • ZW: Female (ZW) or Male (ZZ) in birds and some reptiles

Sub-branches

• SRY gene on Y chromosome: triggers male development
• X-inactivation: process by which one X chromosome is inactivated in females to prevent double gene dosage

Environmental Sex Determination

• The sex of an individual is determined by environmental factors
• Common in reptiles and some fish
• Examples of environmental factors:
  • Temperature
  • Social cues
  • Chemical cues

Sub-branches

• Temperature-dependent sex determination (TSD): sex determined by temperature during critical period of development
• Hormonal sex reversal: exposure to hormones can cause an individual to develop as the opposite sex

Sex Determination in Mammals

Central Idea

• The process of determining the sex of a mammal

Main Branches

1. Genetic Sex Determination
2. Environmental Sex Determination

Genetic Sex Determination

• Determined by the presence or absence of sex chromosomes
• Two types of sex chromosomes: X and Y
• XX = Female, XY = Male

Sub-branches

• Sex-linked traits
• Sex chromosome abnormalities

Environmental Sex Determination

• Determined by environmental factors
• Temperature-dependent sex determination (TSD)
• Social cues and behavior

Sub-branches

• TSD in reptiles and some fish
• Social cues and behavior in primates and some rodents

Conclusion

• Sex determination in mammals can be genetic or environmental, and understanding the mechanisms behind it can provide insight into the evolution and diversity of sex determination systems.