Cytokinesis	Karyokinesis
It is the cell division of cytoplasm that occurs during the M phase of the cell cycle.	It is the separation of daughter chromosomes corresponding to M phase of cell cycle

Question - 3 : - Describe the events taking place during interphase.

Answer - 3 : -

Events taking place during interphase are as follows:

G1 phase (Gap 1) – During this stage, the cell is metabolically active. It grows and prepares the DNA to replicate.
S phase (Synthesis) – During this stage, the synthesis of DNA takes place. The DNA quantity doubles whereas the number of chromosomes remains unchanged
G2 phase (Gap 2) – During this phase, the cell advances to grow and prepare itself for division. It is during this stage that the RNA and proteins that are required for mitosis are generated.

Question - 4 : - What is Go (quiescent phase) of cell cycle?

Answer - 4 : -

In adult animals some cells will not exhibit the cell division, and many other cells occasionally divide when there is need to replace cells that have lost because of injury or cell death. These cells exit the G1 phase to enter inactive stage of the cell cycle called G0 phase. Cells in G0 phase do not proliferate unless called on to do so. Hence, the cells in this phase tend to become inactive, stop dividing and become specialized through the differentiation process.

Question - 5 : - Why is mitosis called equational division?

Answer - 5 : -

Mitosis is called equational division because the number of chromosomes in the parent and progeny cells is the same.

Question - 6 : -
Name the stage of cell cycle at which one of the following events occur:

(i) Chromosomes are moved to spindle equator.
(ii) Centromere splits and chromatids separate.
(iii) Pairing between homologous chromosomes takes place.
(iv) Crossing over between homologous chromosomes takes place.

Answer - 6 : -

i) Chromosomes are moved to the spindle equator in the Metaphase.

ii) Centrosomes split and chromatids separate in the Anaphase

iii) Pairing between homologous chromosomes takes place in the Zygotene stage of prophase 1 in meiosis

iv) Crossing over between homologous chromosomes takes place during the Pachytene stage of prophase 1in meiosis

Question - 7 : -
Describe the following:

(a) synapsis (b) bivalent (c) chiasmata

Draw a diagram to illustrate your answer.

Answer - 7 : -

a) Synapsis – Homologous chromosomes pair together during Zygotene of prophase-I of meiosis. This pairing is called synapsis.

b) Bivalent or tetrad is the pair of complex formed by a pair of synapsed homologous chromosome during the zygotene of prophase I of meiosis.

c) Chiasmata

During diplotene, the paired chromosomes form an X-shaped structure known as chiasmata. At chiasmata, the crossing over between two non-sister chromatids takes place.

Question - 8 : - How does cytokinesis in plant cells differ from that in animal cells?

Answer - 8 : -

Plant cytokinesis	Animals cytokinesis
Occurs by cell plate formation	Takes place by cleavage
Cell plate moves to the centre and extends towards the exterior	Cleavage begins at the periphery and advances inwards
The fusion of vesicles originates in cell plate formation	Cleavge starts with contraction of a peripheral ring of microfilaments
Midbody is not formed	Midbody is formed with dense material in the middle of the cell.

Question - 9 : - Find examples where the four daughter cells from meiosis are equal in size and where they are found unequal in size.

Answer - 9 : -

During formation of male gametes in human beings (sperms), four daughter cell formed during meiosis are equal in size. The formation of female gamete (ovum) during meiosis results in formation of four daughter cells, unequal in size. The unequal daughter cells are – one big mature ovum and 3 small polar bodies.

Question - 10 : - Distinguish anaphase of mitosis from anaphase I of meiosis.

Answer - 10 : -

Anaphase of mitosis	Anaphase I of meiosis
Anaphase is the stage during which the centromere splits and the chromatids separate. The chromosomes move apart, toward the opposite poles. These chromosomes are genetically identical.	During anaphase I, the homologous chromosomes separate, while the chromatids remain attached at their centromeres.Hence, in anaphase I, the chromosomes of each bivalent pair separate, while the sister chromatids remain together.

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Chapter 10 Cell Cycle and Cell Division Solutions

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