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.

• 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.

Astral body are formed of microtubules. Astral bodies are produced by centriole during cell division and attach with centromere of the chromosome.

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.

Human nerve cells do not divide after birth. The neural system is the control system of the body which consists of highly specialized cells called neurons. Nerve cell does not divide because they do not have centrioles, so they cannot undergo mitosis and divide to form new 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.

In plant cell, mitosis cell division is generally controlled by cytokinin hormone. Auxinis also required for cell division in plant.

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.

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.

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.

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

During mitosis, Endoplasmic Reticulum (ER) and nucleolus begin to disappear at early prophase and these are not observed in late prophase. 

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

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.

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.

At metaphase stage, the 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.

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

Egg yolk contains lampbrush chromosome where two homologous chromosomes with several chiasmata with several loop in chromatic region is found.

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

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

Colchicine is an alkaloid used in plant breeding for doubling of chromosomeby inhibiting cytokinesis. It is also called as mitotic poison.

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