Page 49 - Biology - XII

(c) Each chromosome has distinct chromatids only attached at centromeres.
(d) The chromosome number is half the original number. (Each group of chromosome is half (n) of
the original number 2n).

Telophase I. This stage is identifi ed by—
(a) The chromosomes at the poles uncoil.

(b) The chromosomes are surrounded by a nuclear membrane. Thus, two daughter nuclei are formed.
(c) Nucleolus reappears within the nucleus.
(A cell membrane may be formed/Cytoplasm division may be followed.)

The daughter nuclei are formed and cytoplasm is divided into two by cell furrow formation. This
results in two daughter cells. Now called as Secondary spermatocytes.
Secondary spermatocytes show the following stages.

Prophase II. This stage is simple and does not include subdivisions 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 distinct.

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 chromosome 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) The daughter cells are formed by cell furrow formation.

(e) The end products are called spermatids. These cells undergo further changes and give rise to
spermatozoa with tail.

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