Oogenesis

Maturation of Oocytes Begins Before Birth

Once primordial germ cells have arrived in the gonad of a genetic female, they differentiate into oogonia (Fig. 1.16, A and B). These cells undergo a number

Figure 1.15 Fluorescence in situ hybridization (FISH) using a probe for chromosome 21. Two interphase cells and a metaphase spread of chromosomes are shown; each has three domains, indicated by the probe, characteristic of trisomy 21 (Down syndrome).

Figure 1.15 Fluorescence in situ hybridization (FISH) using a probe for chromosome 21. Two interphase cells and a metaphase spread of chromosomes are shown; each has three domains, indicated by the probe, characteristic of trisomy 21 (Down syndrome).

Selection Oogonia

germ cell in prophase

Figure 1.16 Differentiation of primordial germ cells into oogonia begins shortly after their arrival in the ovary. By the third month of development, some oogonia give rise to primary oocytes that enter prophase of the first meiotic division. This prophase may last 40 or more years and finishes only when the cell begins its final maturation. During this period it carries 46 double-structured chromosomes.

germ cell in prophase

Figure 1.16 Differentiation of primordial germ cells into oogonia begins shortly after their arrival in the ovary. By the third month of development, some oogonia give rise to primary oocytes that enter prophase of the first meiotic division. This prophase may last 40 or more years and finishes only when the cell begins its final maturation. During this period it carries 46 double-structured chromosomes.

Surface epithelium of ovary

Flat epithelial cell

Primary oocyte in prophase

Oogonia

Primary oocytes in prophase of 1st meiotic division

Primary oocyte in prophase

Flat epithelial cell

Oogonia

Primary oocytes in prophase of 1st meiotic division

First Meiotic Division Oogenesis

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