Observations of chromosomal behaviour in living meiotic zygotes of Chlamydomonas reinhardtii (Chlorophyceae)

Figures & data

Fig. 1. Proportions of zygotes completing the first and second meiotic divisions, counted after exposing the zygotes to light. Dashed line: zygotes completing the first meiotic division. Solid line: zygotes completing the second meiotic division. Vertical line: standard deviation.

Figs 2–21. Fluorescence microscopy of chromosome behaviour during meiosis. Figs 2–9. Chromosome morphology in prophase I. Fig. 3. Leptotene. Fig. 4. Zygotene. Fig. 5. Pachytene. Figs 6–9. Diplotene and diakinesis at approximately 16 h. Figs. 10–21. Metaphase I to telophase II. Fig. 10. Metaphase I. Figs 11–14. Anaphase I. Fig. 15. Telophase I. Fig. 13. The side view shows chromosomes situated at the surface of the zygotes. Fig. 16. Prophase II. Fig. 17. Metaphase II. Figs 18, 19. Anaphase II. Fig. 20. Telophase II. Fig. 21. Formation of four daughter cells. Scale bar: 5 µm.

Figs 22–27. Enlargements of chromosomes at metaphase and anaphase. Figs 22–25. Chromosomes at meiosis I, as shown in fluorescent photomicrographs of enlarged portions of the nuclei in Figs 10–12, 14, respectively. Figs 26, 27. Chromosomes at meiosis II (enlarged portions of the nuclei in Figs 18, 19). Scale bar: 5 µm.

Figs 28–31. Fluorescence micrographs of chromosomes at meiotic diakinesis at different focal planes of the same zygote. Fig. 28. Low. Fig. 29. Middle. Fig. 30. Upper. Fig. 31. Composite image based on the superimposition of views Figs 28–30. Scale bar: 5 µm.

Figs 32–35. Fluorescent photomicrographs of spread chromosomes at diakinesis. Figs 32, 34. Total chromosomes spread on glass slide. Figs 33, 35. Chromosomes arranged in order of fluorescence intensity. Scale bar: 5 µm.

Table. 1.  Relative fluorescence intensity and estimation of DNA quantity of each chromosome.

Chromosome number	Image I	Image II	Image III	Image IV	Average	DNA quantities of each chromosome (Mb)
1	1.00	1.00	1.00	1.00	1.00 (0.00)	12.75
2	0.80	0.82	1.00	0.90	0.88 (0.09)	11.22
3	0.78	0.57	0.80	0.79	0.73 (0.11)	9.35
4	0.77	0.54	0.78	0.73	0.70 (0.11)	8.99
5	0.73	0.50	0.75	0.71	0.67 (0.12)	8.57
6	0.68	0.45	0.74	0.62	0.62 (0.12)	7.94
7	0.68	0.42	0.70	0.51	0.58 (0.14)	7.39
8	0.61	0.37	0.67	0.49	0.53 (0.13)	6.81
9	0.60	0.36	0.65	0.47	0.52 (0.13)	6.58
10	0.56	0.34	0.61	0.40	0.48 (0.13)	6.10
11	0.46	0.31	0.51	0.40	0.42 (0.09)	5.36
12	0.46	0.28	0.49	0.39	0.41 (0.09)	5.19
13	0.45	0.26	0.45	0.35	0.38 (0.09)	4.84
14	0.42	0.25	0.44	0.34	0.36 (0.09)	4.61
15	0.42	0.23	0.42	0.32	0.35 (0.09)	4.43
16	0.42	0.21	0.36	0.27	0.31 (0.09)	4.00
17	0.39	0.20	0.35	0.21	0.29 (0.10)	3.67
18	0.39	0.17	0.26	0.19	0.25 (0.10)	3.20
					Total genome	121.00
DNA content was estimated from the average fluorescence intensity of four images. Standard deviation is given in parenthesis.