MEIOSIS

 

General Cell Structures

[Hypothetical cell, 2n = 6]

 

1          cell membrane (plasma membrane)

2          cytoplasm

3          nucleus

4          nucleolus

5          centrioles

6          aster

7          chromatin threads (condensed)

8          spindle in process of formation

9          spindle fiber

10        chromosome

11        chromatid (2 arms)

12        centromere

 

Cell Structures Unique to Meiosis

13        primary spermatocyte (prophase I)

13a      early metaphase I

13b      anaphase I (sister chromatids do not      separate)

14        secondary spermatocyte

            (early prophase II)

14a      secondary spermatocyte

            (anaphase II)

15        spermatids

16        spermatozoa (sperm)

17        primary oocyte (prophase I)

17a      metaphase I

18        secondary oocyte (forming)

19        first polar body (forming)

20        ootid (secondary oocyte)

            in anaphase II

21        second polar bodies (one in process of

            dividing, two complete;  NOTE: 

            penetration of sperm is usually what

            triggers completion of meiosis II)

22        ovum (egg)

23        diploid cell (after fertilization, preparing

            for first mitotic division or cleavage)