Test: Cell Cycle & Cell Division - 2 - NEET MCQ

The root tip cells of onion were used to test the potentially genotoxic effects of Alprazolam. The test was carried out according to Fiskesjö protocol (4, 11-12) with some modifications. Common onion (Allium cepa L.) has eight pairs of relatively large chromosomes (2n = 16) that allows for the easy detection of CAs.

Topic in NCERT: Cell cycle and cell division

Line in NCERT: "you have studied mitosis in onion root tip cells. it has 16 chromosomes in each cell."

• The haploid phase of life cycle occurs when the total chromosome number inside the cell is reduced to half.
• It occurs by the process of meiosis.
• Fertilization restores the diploid phase of life cycle.

Topic in NCERT: Meiosis

Line in NCERT: "meiosis ensures the production of haploid phase in the life cycle of sexually reproducing organisms whereas fertilisation restores the diploid phase."

Small disc-shaped structures at the surface of the centromeres are called kinetochores. These structures serve as the sites of attachment of spindle fibres (formed by the spindle fibres) to the chromosomes.

Topic in NCERT: Metaphase

Line in NCERT: "small disc-shaped structures at the surface of the centromeres are called kinetochores."

During the G2 phase, proteins are synthesised in preparation for mitosis while cell growth continues.

Topic in NCERT: G2 phase (gap 2)

Line in NCERT: "in animal cells, during the g2 phase, proteins are synthesised in preparation for mitosis while cell growth continues."

If cytokinesis doesn't take place after karyokinesis, formation of daughter cells from the parent cell doesn't take place. The parent cell will have more than one nucleus, which are supposed to be present in daughter cells.

If it's a plant cell, cell plate formation doesn't take place.

If it's an animal cell, a furrow doesn't appear.

Cytokinesis means division of cytoplasm. So, the cytoplasmic division doesn't take place after the division of nucleus(karyokinesis).

Hence, the correct answer is Option D.

Topic in NCERT: M phase

Line in NCERT: "in some organisms karyokinesis is not followed by cytokinesis as a result of which multinucleate condition arises leading to the formation of syncytium."

Solution : 

The correct option is Option B,

c, a, d, b

During the anaphase II stage of meiosis, the following events take place in the following order:

1. Centromeres split and chromatids separate: During anaphase II, the centromere of each chromosome splits, and the two chromatids that were previously joined at the centromere move to opposite poles of the cell. This is the first event that occurs during anaphase II.

2. Metaphase plate splits: During anaphase II, the metaphase plate, which is the line along which the chromosomes are aligned during metaphase, splits into two halves. This is the second event that occurs during anaphase II.

3. Chromatids move to opposite poles: As the metaphase plate splits, the chromatids that were previously aligned along it move towards the poles of the cell. This is the third event that occurs during anaphase II.

4. Each chromosome moves away from the equatorial plane: As the chromatids move towards the poles, the chromosomes they make up also move away from the equatorial plane of the cell. This is the final event that occurs during anaphase II.

Therefore, the correct order of events is c, a, d, b.

Topic in NCERT: Anaphase

Line in NCERT: "at the onset of anaphase, each chromosome arranged at the metaphase plate is split simultaneously and the two daughter chromatids, now referred to as daughter chromosomes of the future daughter nuclei, begin their migration towards the two opposite poles."
"centromeres split and chromatids separate."
"chromatids move to opposite poles."

In diploid cells, each homologous pair consists of one paternal and one maternal chromosome. These chromosomes are not fused together. Instead, each homologous pair contains one chromosome inherited from each parent, forming pairs that are separate entities within the cell.

Topic in NCERT: Meiosis i

Line in NCERT: "meiosis involves pairing of homologous chromosomes and recombination between non-sister chromatids of homologous chromosomes."

The interphase, though called the resting phase, is the time during which the cell is preparing for divisionby undergoing both cell growth and DNA replication in an orderly manner.

Topic in NCERT: Interphase

Line in NCERT: "the interphase, though called the resting phase, is the time during which the cell is preparing for division by undergoing both cell growth and dna replication in an orderly manner."

Mitosis is also divided into four stages namely prophase, metaphase, anaphase and telophase.

Topic in NCERT: M phase

Line in NCERT: "though for convenience mitosis has been divided into four stages of nuclear division (karyokinesis), it is very essential to understand that cell division is a progressive process and very clear-cut lines cannot be drawn between various stages. karyokinesis involves following four stages: prophase, metaphase, anaphase, telophase."

During mitosis, the Endoplasmic Reticulum (ER) and nucleolus begin to disappear at late prophase. This is when the nuclear envelope also breaks down, marking the end of prophase.

Topic in NCERT: Cell cycle and cell division

Line in NCERT: "cells at the end of prophase, when viewed under the microscope, do not show golgi complexes, endoplasmic reticulum, nucleolus and the nuclear envelope."

Meiosis cell division results into number of chromosome reduce to half, recombination of genes and formation of spores and gametes.

Topic in NCERT: Significance of meiosis

Line in NCERT: "meiosis is the mechanism by which conservation of specific chromosome number of each species is achieved across generations in sexually reproducing organisms, even though the process, per se, paradoxically, results in reduction of chromosome number by half."

Polyploidy is the condition in which more than one set of chromosome is present in one cell. It is the property of increasing the number of chromosomes sets of the cell.

Topic in NCERT: Meiosis i

Line in NCERT: "meiosis involves pairing of homologous chromosomes and recombination between non-sister chromatids of homologous chromosomes."

Option 3: Diploid somatic cells.

During mitotic division, also known as cell division, the genetic material in a cell's nucleus is replicated and then the cell divides into two daughter cells. In animal cells, this process occurs in diploid somatic cells, which are cells that contain two copies of each chromosome (one from each parent). Haploid cells, on the other hand, only contain one copy of each chromosome. Haploid cells can be either germ cells, which are cells that give rise to gametes (sperm or eggs), or they can be cells that have undergone meiosis, a type of cell division that reduces the chromosome number by half.

Topic in NCERT: Mitosis

Line in NCERT: "in animals, mitotic cell division is only seen in the diploid somatic cells."

At metaphase stage, the chromosome is made up of two sister chromatids, which are held together by the centromere.

Topic in NCERT: Metaphase

Line in NCERT: "at this stage, metaphase chromosome is made up of two sister chromatids, which are held together by the centromere."

In animal cell, cytokinesis takes place by furrow deepening centripetally and formation of two daughter cells. This method of cytokinesis is known as cleavage cytokinesis.

Topic in NCERT: Cytokinesis

Line in NCERT: "in an animal cell, this is achieved by the appearance of a furrow in the plasma membrane. the furrow gradually deepens and ultimately joins in the centre dividing the cell cytoplasm into two."

In telophase I, the nuclear membrane and nucleolus reappear.Meiosis II is similar to mitosis.

Topic in NCERT: Telophase i

Line in NCERT: "telophase i: the nuclear membrane and nucleolus reappear, cytokinesis follows and this is called as dyad of cells (figure 10.3)."

The quiescent stage (G0) of the cell cycle. Cells in this stage remainmetabolically active but no longer proliferate unless called on to do so.

Topic in NCERT: Quiescent stage of the cell cycle

Line in NCERT: "these cells that do not divide further exit g₁ phase to enter an inactive stage called quiescent stage (g₀) of the cell cycle. cells in this stage remain metabolically active but no longer proliferate unless called on to do so depending on the requirement of the organism."

During prophase, the chromosomes condense, the nucleolus disappears, and the nuclear envelope breaks down.

Topic in NCERT: Cell cycle and cell division

Line in NCERT: "cells at the end of prophase, when viewed under the microscope, do not show golgi complexes, endoplasmic reticulum, nucleolus and the nuclear envelope."

Synapsis occur between two homologous chromosome during zygotene phase of prophase of meiosis I due to presence of synaptical complex between homologous chromosomes.

Topic in NCERT: Prophase i

Line in NCERT: "during this stage chromosomes start pairing together and this process of association is called synapsis. such paired chromosomes are called homologous chromosomes."

Spindle fibres attach to kinetochores of chromosomes during cell division. They help the chromosomes/chromatids to get separated to the two daughter cells, towards opposite poles.

Topic in NCERT: Metaphase

Line in NCERT: "spindle fibres attach to kinetochores of chromosomes."