Polar Bodies

Also during meiosis one primary oocyte gives rise to four daughter cells, each with 22 plus 1 X chromosomes (Fig. 1.4A). However, only one of these develops into a mature gamete, the oocyte; the other three, the polar bodies, receive little cytoplasm and degenerate during subsequent development. Similarly, one primary spermatocyte gives rise to four daughter cells, two with 22 plus 1

Mature Gamete

Figure 1.3 First and second meiotic divisions. A. Homologous chromosomes approach each other. B. Homologous chromosomes pair, and each member of the pair consists of two chromatids. C. Intimately paired homologous chromosomes interchange chromatid fragments (crossover). Note the chiasma. D. Double-structured chromosomes pull apart. E. Anaphase of the first meiotic division. F and G. During the second meiotic division, the double-structured chromosomes split at the centromere. At completion of division, chromosomes in each of the four daughter cells are different from each other.

Figure 1.3 First and second meiotic divisions. A. Homologous chromosomes approach each other. B. Homologous chromosomes pair, and each member of the pair consists of two chromatids. C. Intimately paired homologous chromosomes interchange chromatid fragments (crossover). Note the chiasma. D. Double-structured chromosomes pull apart. E. Anaphase of the first meiotic division. F and G. During the second meiotic division, the double-structured chromosomes split at the centromere. At completion of division, chromosomes in each of the four daughter cells are different from each other.

X chromosomes and two with 22 plus 1 Y chromosomes (Fig. 1.4B). However, in contrast to oocyte formation, all four develop into mature gametes.

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