Q: How does cytokinesis in plant cells differ from that in animal cells?

\$\textbf{Solution:}\$\$\bullet\$ Cytokinesis occurs in mitosis and meiosis for both plant and animal cells. The ultimate objective is to divide the parent cell into daughter cells.\$\bullet\$ Cytokinesis in animal cells occurs by furrowing of the cytoplasm.\$\bullet\$ Furrow starts at the periphery and then moves inward, dividing the cell into two parts.\$\bullet\$ In plant cells, cytokinesis is initiated with the formation of a cell plate in the middle of the cell.\$\bullet\$ Cell plate formation starts at the center of the cell and grows outward, toward the lateral walls.

Q: Identify the correct order of phases for the cell cycle?I. G\$_2\$ phase- growth and preparation for mitosisII. MitosisIII. G\$_1\$phase- cell growthIV. S phase - DNA copiedV. Cytokinesis

The correct order of phases of cell cycle: Interphase (G₁, S, and G₂ phases), mitotic phase (mitosis and cytokinesis), and G₀ phase.G\$_1\$ phase also called the first gap phase, the cell grows larger and makes more of its ribosomes, organelles, and proteins. This phase ensures that division will produce functional daughter cells, ones that are the right size and have all the parts they need. S phase. In order to divide, a cell also needs to make a copy of its genetic material, allowing it to give one full set to each of its two daughter cells. To accomplish this, the cell moves from G\$_1\$ into a phase called S phase, during which it synthesizes a complete copy of the DNA in its nucleus. Once DNA synthesis is complete, the cell enters a second gap phase, called G\$_2\$ phase. During this period, the cell grows more, makes additional proteins and organelles, and begins to reorganize its contents in preparation for mitosis, the separation of the copied DNA into two equal sets. G2 phase ends when mitosis begins. Interphase alternates with mitotic (M) phase. During M phase, the cell divides its copied nuclear DNA and cytoplasm to form two new cells. M phase is further divided into two phases: mitosis and cytokinesis. In mitosis, the nuclear DNA of the cell condenses into visible chromosomes and is pulled apart by the mitotic spindle, a specialized structure made out of microtubules. Mitosis takes place in four stages: prophase metaphase, anaphase, and telophase. In cytokinesis, the cytoplasm of the cell is split in two, making two new cells. Cytokinesis usually begins just as mitosis is ending, with a little overlap. So, the correct answer is option A.

Question 1

List the main differences between mitosis and meiosis?

Accepted Answer

Answer-Mitosis Meiosis1) This division takes place in somatic cells and as a result of this division, growth occurs.  1) This takes place usually in reproductive cells and as a result of this character one generation pass into the other.2) Completed in one stage. 2) Completed in two stages.3) Prophase is smaller (as compared to prophase of Meiosis). 3) Prophase longer than prophase of mitosis and divided into five substages. 4) Crossing over does not take place. 4) Crossing over takes place in which the exchange of segments of chromatids occurs. 5) Synapsis does not take place at metaphase. 5) Synapsis between homologous chromosomes takes place (bivalent stage). 6) At metaphase, the centromere is towards the equatorial plate and ends of chromosomes towards poles. Centromere divides. 6) At metaphase I, the centromere is towards poles and ends of chromosomes towards the equatorial plate. Centromere does not divide. 7) Chromatids are long and thin.7) Chromatids are shorter and thick  8) Cytokinesis follows karyokinesis. 8) After Telophase I, cytokinesis does not take place always (may occur).

Question 2

Explain the stages of prophase I of meiosis.

Accepted Answer

The prophase I of meiosis occurs in the following stages:1. Leptotene- This phase is the start of prophase-I. It is marked by the condensation of the chromosomes.2. Zygotene- In this phase the homologous chromosomes start pairing up, called the synapsis. The synaptonemal complex starts building up. This complex is required to hold the homologous chromosomes at a place close to each other. Bivalent chromosomes are visible at this stage.3. Pachytene- In this stage, this non-sister chromatids of homologous chromosomes exchange their parts, the process is called the crossing over. The attachment point of the crossing-over of the non-sister chromatids is called chiasma.4. Diplotene- The crossing-over process is completed by this stage. The homologous chromosomes remain attched at the point of chiasma.5. Diakinesis- The homologous chromosomes start to separate and synaptonemal complex disappears. The nuclear membrane also disappears.

Question 3

What is the significance of meiosis?

Accepted Answer

Meiosis is a type of cell division that reduces the number of chromosomes in the parent cell by half and produces four gamete cells.The significance of meiosis is in-Formation of gametes &#8722; Meiosis form gametes that are essential for sexual reproduction.Genetic information &#8722; Meiosis switches on the genetic information for the development of gametes.Crossing over &#8722; It introduces new combination of traits or variations.Mutation &#8722; Mutations take place due to irregularities of meiotic division.

Question 4

How does cytokinesis in plant cells differ from that in animal cells?

Accepted Answer

$\textbf{Solution:}$$\bullet$ Cytokinesis occurs in mitosis and meiosis for both plant and animal cells. The ultimate objective is to divide the parent cell into daughter cells.$\bullet$ Cytokinesis in animal cells occurs by furrowing of the cytoplasm.$\bullet$ Furrow starts at the periphery and then moves inward, dividing the cell into two parts.$\bullet$ In plant cells, cytokinesis is initiated with the formation of a cell plate in the middle of the cell.$\bullet$ Cell plate formation starts at the center of the cell and grows outward, toward the lateral walls.

Question 5

The correct sequence of different phases of mitosis is

Accepted Answer

Mitosis consists of four basic phases: prophase, metaphase, anaphase, and telophase.  These phases occur in this strict sequential order, and cytokinesis - the process of dividing the cell contents to make two new cells - starts in anaphase or telophase. The mitotic phase is a relatively short period of the cell cycle. It alternates with the much longer interphase, where the cell prepares itself for the process of cell division. Interphase is divided into three phases: G1 (first gap), S (synthesis), and G2 (second gap). Hence the correct answer is option D.

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.

Accepted Answer

(i) Metaphase(ii) Anaphase(iii) Zygotene of meiosis I(iv) Pachytene of meiosis I

Question 7

Arrange the following events of meiosis in correct sequence (a) Crossing over (b) Synapsis (c) Terminalisation of chiasmata (d) Disappearance of nucleolus.

Accepted Answer

Correct Answer: (B) b, a, c, dExplanation:During Meiosis I the first step is synapsis to form the synaptonemal complex.After that crossing over between the homologous chromosome takes place.Then after crossing over terminalisation of chiasmata happens.After that, the nucleolus gets disappeared.Hence, option (B) is the correct sequence of meiosis.

Question 8

Write the differences between mitosis and meiosis.

Accepted Answer

S.No Mitosis Meiosis 1It takes place in both Haploid cells and diploid cellsIt takes place only in diploid cells. 2It takes place in all body cells or vegetative cells or somatic.It takes place in reproductive cells or germinal cells. 3Nucleus divides onceNucleus divides twice to produce 4 nuclei. 4Daughter cells are identical to mother cellsDaughter cells are not identical. 5 Chromosomes do not pairHomologous chromosomes (similar) pair to form bivalent ones. 6Chiasmata is absent, Also there is no crossing overChiasmata present. Crossing over between non-sister chromatids occurs. 7The chromosome number in the daughter cell is unchanged.Chromosome number is reduced to half of the parent cell.  8The entire cell division is short comparatively.The duration of cell division is very large as it involves many steps. 9It helps for the growth of the body and in lower forms like bacteria, to multiply organism numbers.It helps in gamete formation for sexual reproduction.

Question 9

The four daughter cells produced at the end of meiosis are?

Accepted Answer

During meiosis, one cell divides twice to form four different daughter cells. These cells have only half the number of chromosomes of the parent. That is, they are haploid.Meiosis produces gametes (eggs in females and sperm in the male). The four daughter cells produced are genetically dissimilar to the parent cell because the parent cell is always diploid while daughter cells are haploid in nature.So the correct option is C

Question 10

Identify the correct order of phases for the cell cycle?I. G$_2$ phase- growth and preparation for mitosisII. MitosisIII. G$_1$phase- cell growthIV. S phase - DNA copiedV. Cytokinesis

Accepted Answer

The correct order of phases of cell cycle: Interphase (G&#8321;, S, and G&#8322; phases), mitotic phase (mitosis and cytokinesis), and G&#8320; phase.G$_1$ phase also called the first gap phase, the cell grows larger and makes more of its ribosomes, organelles, and proteins. This phase ensures that division will produce functional daughter cells, ones that are the right size and have all the parts they need.&#10;&#10;S phase. In order to divide, a cell also needs to make a copy of its genetic material, allowing it to give one full set to each of its two daughter cells. To accomplish this, the cell moves from G$_1$ into a phase called S phase, during which it synthesizes a complete copy of the DNA in its nucleus.&#10;&#10;Once DNA synthesis is complete, the cell enters a second gap phase, called G$_2$ phase. During this period, the cell grows more, makes additional proteins and organelles, and begins to reorganize its contents in preparation for mitosis, the separation of the copied DNA into two equal sets. G2 phase ends when mitosis begins.&#10;&#10;Interphase alternates with mitotic (M) phase. During M phase, the cell divides its copied nuclear DNA and cytoplasm to form two new cells. M phase is further divided into two phases: mitosis and cytokinesis.&#10;&#10;In mitosis, the nuclear DNA of the cell condenses into visible chromosomes and is pulled apart by the mitotic spindle, a specialized structure made out of microtubules. Mitosis takes place in four stages: prophase metaphase, anaphase, and telophase. &#10;&#10;In cytokinesis, the cytoplasm of the cell is split in two, making two new cells. Cytokinesis usually begins just as mitosis is ending, with a little overlap. So, the correct answer is option A.