CBSE Questions for Class 11 Medical Biology Cell Cycle And Cell Division Quiz 2 - MCQExams.com

Metaphase is the best stage to count the total number of chromosomes in any species and to establish a detailed study of the morphology of the chromosomes. As mitotic cells are easy to obtain, morphological studies are generally based on mitotic metaphase chromosomes. In this stage, the centrioles are at opposite poles of the cell. The homologous chromosome pairs (the bivalents), are tightly coiled and condensed and become arranged on a plane called the metaphase plate or equatorial plate. This plate is equidistant from the poles. Discontinuous fibres radiate out from the two poles and get connected to kinetochores at the surface of the centromere. A kinetochore is complex protein structure and a point where microtubules attach themselves to the chromosome. When the chromosomes get arranged at the metaphase plate, smaller chromosomes get directed towards the centre while the larger ones are peripheral in position on the equator. The centromeres of all the chromosomes lie on the equator forming an apparent plate called metaphasic or equatorial plate while arms are directed towards the poles.

The correct answer is option C.

• Meiosis is the division where the cell after dividing produces 4 daughter cells where the genetic material is halved as compared to the mother cells.
• Meiosis is divided into meiosis 1 and meiosis 2. In every meiosis the nucleus is divided once.
• And after the meiosis 1 the nucleus is divided once and the chromosomes are halved during this meiosis.
• In the meiosis 2 the chromosomes are not divided but the nucleus is divided once
• This way 4 nucleus are formed after one meiosis and the chromosomes are halved.
• Meiosis takes place in the formation of gametes where the genetic material is required to be halves for the formation of haploid gametes.
• Therefore the answer option 'two nuclear divisions with chromosomes dividing only once' is correct.
  

• Cytokinesis is the formation of cell after the cell division.
• The cell division is made up of 4 phases which are prophase, metaphase, anaphase and telophase.
• The lase phase i.e. the telophase is where the genetic material of the dividing cells is pulled to their respective poles by the spindle fiber and the nuclear membrane starts to reappear.
• The constriction of the plasma membrane also starts which is the part of the cytokinesis process and this process overlaps with the telophase which is the last one in the cell cycle.
• as this process overlaps the telophase sometimes in plants or animals also where 2 cells are observed with proper cell wall and nucleus but are still attached to each other as the telophase and the cytokinesis are overlapping each other.
  
• Therefore the answer option 'Telophase' is correct.
  

• In meiosis, the number of chromosomes gets halved. 
• In anaphase I of meiosis I, the chromosomes move towards the spindle poles along the path of their tactile fibrils. 
• The two groups of chromosomes are produced with each group having half the number of chromosomes present in the parent nucleus.
• In mitosis and amitosis (cell division), the number remains the same.
• In fertilization, there is a fusion of two cells results in the combining of genetic material in a cell (or formation of zygote).

• Goblet cells are simple columnar epithelial cells that secrete mucous.
• Goblet cells are found scattered among the epithelial lining of organs, such as the intestinal and respiratory tracts. They are found inside the trachea, bronchi, and larger bronchioles in the respiratory tract, small intestines, the large intestine, and conjunctiva in the upper eyelid.
  
• Hence Goblet cell is found in mucus-secreting cells.
• So, the correct answer is 'Goblet cells'.

• The division of cytoplasm is termed as cytokinesis. It happens in the final stage of mitosis which is a form of asexual cellular division.
• Mitosis has four different stages known as prophase, metaphase, anaphase, and telophase. Cytokinesis is a stage at which the cell furrow is being cut to form two identical daughter cells from the parent cell.
• Whereas, karyokinesis refers to the cell nucleus division during mitosis. It is usually followed by cytokinesis. Crossing over is a term used to refer to the exchange of genetic material between two homologous chromosomes.

Correct option: B.
Explanation:

• It is given that the diploid chromosome number is 8 (2n).
• It contains 16 chromatids.
• Meiosis I starts with the diploid (2n) cells and ends with the haploid (n) daughter cells.
• Since, before meiosis I, the cell contains 16 (2n) chromatids, the number of chromatids in each daughter cell after meiosis I will be 8 (n).

• Meiosis occurs in germ cells which form gametes. Germ cells are diploid cells which undergo meiosis to form haploid cells.
• Meiosis leads to independent assortment of maternal and paternal chromosomes, hence, it helps in bringing haplophase.
• When male and female gametes fuse, a diploid zygote is formed restoring the chromosome number to that of the species.

• 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.

• Mitosis is a process of cell division through which the cells in our body divide into two daughter cells. It is seen in eukaryotic cells such as animal and plant cells. In humans, mitosis occurs in somatic cells and helps in the growth and also repairs any genetic damage that has occurred. 
• Meiosis occurs in the reproductive cells to give 4 daughter cells which are haploid (1 set of chromosomes) where mitotic daughter cells are diploid (2 sets of chromosomes) matching with the parent cell. Thus, meiosis helps in reproduction, but not in the growth of an organism.  
• Cell cycle includes a series of events that occur in the cell division such as from DNA replication to cytoplasm division for the production of two daughter cells. 

• Prophase of meiosis is long and complex. Prophase I or prophase of first meiotic division is comprised of Leptotene, zygotene, pachytene, diplotene, and diakinesis.
• It is during prophase I, that crossing over occurs between homologous chromosomes.
  Hence, option B is correct.