Lecture 12.3

• Egg development is called oogenesis.
• Oogenesis is asymmetrical, the four produced haploids are not identical.
• Primary oocytes enter meiosis 1 during female embryonic development.
• Sperm development in humans is called spermatogenesis.
• Spermatogenesis is symmetrical and instantaneous.
• Down syndrome is a nondisjunction of trisomy 21.