Page 46 - Biology - XII

Prophase II. This stage is simple and does not include sub-divisions like prophase I.
This stage is identifi ed by—

(a) There are two daughter cells attached to each other.
(b) The chromosomes become distinct once again in two daughter nuclei at the poles.
(c) The nuclear membranes lose their identity and nucleolus start to disappear.
(d) Chromatids are distinctive.

Metaphase II. This stage is identifi ed by—
(a) The nuclear membrane, nucleolus have disappeared.
(b) The chromosome sets are free at the opposite poles.
(c) The chromosomes are at the equators of the two daughter cells.

(d) The chromosomes are attached to spindle fi bres.
(e) Thus, two sets of spindles are formed.
Anaphase II. This stage is identifi ed by—

(a) The centromere of each chromosomes divides.
(b) The chromatids of the chromosomes move apart.
(c) The chromosomes shift to opposite poles.
(d) They are in shapes of J, V, or U.

(e) Four sets of chromosomes appear in two daughter cells (two sets in each daughter cell).
Telophase II. This stage is identifi ed by—
(a) The chromosomes at poles form chromatin network.
(b) The nuclear membrane, nucleolus reappear.

(c) Four daughter nuclei are formed in the two daughter cells (two sets in each daughter cell).
(d) These daughter nuclei are separated by cell plate formation.
(e) The end products are called microspores or pollen grains.
These pollen grains are enclosed in a common callose wall. This state is called tetrad (compound
pollen grains).

SPOT - 2

Meiosis in Testis of Grasshopper—Schistocerca
Draw the fi gure and write comments in your practical record fi le.

Observations
1. Cells are of diff erent shapes and sizes.
2. Spermatocytes are primary (undergoing meiosis-I) and secondary (undergoing meiosis-II). They are
big in size.
3. Spermatids are small cells with deeply stained nucleus and little cytoplasm.

4. Spermatozoa are cells with small tails at one end.

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