Oogenesis is the process of producing the female gamete

Last updated: 6/29/2023

Oogenesis is the process of producing the female gamete reproductive cell by meiosis reductive division The purpose of oogenesis is to reduce the chromosome number in the gamete from dip loid 2n the total number of 46 chromosomes to haploid n half the total chromosome number of 23 chromosomes Therefore at fertilization the diploid number is restored with half the genetic information from each parent before Oogenesis consists of two mitotic divisions meiosis I and meiosis II and begins in the ovary birth with diploid stem cells called oogonia They soon divide to form millions of germ cells most of which degenerate Some of the surviving ones develop into the primary oocyte 2n The primary oocyte begins the first meiotic division and then stops in prophase I Here it remains until puberty At puberty several primary oocytes divide each month to form two unequal haploid n cells The larger one the secondary oocyte contains most of the cytoplasm and will become the ovum The smaller one is called the first polar body and will eventually degenerate The secondary oocyte begins meiosis II but stops just before ovulation release from the ovary It will not complete meiosis II unless it is fertilized At that time it will complete the second meiotic division and form an ovum and second polar body When the sperm nucleus n unites with the ovum nucleus n a zygote 2n is formed Exercise 5 Oogenesis Label the cells of oogenesis in Figure 13 6 by writing its number in the blank before its name Before birth Each month from puberty to menopause If fertilization occurs Begins Meiosis I and stops in Prophase I 3 Completes Meiosis I 6 Ovulation Completes Meiosis II 20 2 5 7 8 Word Bank first polar body oogonium ovum primary oocyte second polar body secondary oocyte sperm cell zygote