Cell Cycle and Cell Division Important Questions

Cell Cycle and Cell Division Important Questions helps in the preparation of the final exams as well as competitive examinations. The important questions covered in the article discusses the concepts of cell division, cell cycle, and mitosis. 

Cell cycle or cell division is defined as the series of events that take place in cells which is followed by its maturity and subsequent division. Cell division is a very important process that takes place in living organisms.Cell cycle is termed as the sequence of events a cell passes through, as it divides and produces new cells. The two phases in which a cell cycle is divided are interphase and the M phase, or Mitosis. A cell spends the majority of its time in interphase, it grows, duplicates its chromosomes, and prepares for the division.

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Cell Cycle and Cell Division Important Questions

Very Short Answer Questions [1 Marks Question]

Ques: What is the stage of cell division in which paired homologous chromosomes get short and thick?

Ans: Pachytene is a stage of cell division during which paired homologous chromosomes become shorter and thicker. The pachytene stage starts with the completion of synapsis. 

Ques: Which human body part can be used to depict the stages of mitosis?

Ans: All cells in the human body are somatic cells, with the exception of germinal cells. For regeneration and growth, somatic cells divide by mitosis, which can be used to demonstrate mitosis.

Ques: Does meiosis occur in a variety of plant and animal tissues?

Ans: Yes, meiosis occurs in plants and animals. Meiosis occurs in the sex cells or germ cells of female and male reproductive organs in animals and plants, resulting in the production of female and male gametes for sexual reproduction.

Ques: Which cell among eukaryotes and prokaryotes has the shorter cell division time?

Ans: In comparison to eukaryotic cells, prokaryotic cells have a shorter cell cycle. The cell division process of prokaryotes is less complicated and is a faster process than the cell division in eukaryotes.

Ques: The asters of the spindle are formed by which animal cell structure?

Ans: The centrosome is the component of an animal cell that generates the spindle's asters. The centrosome is present only in the animal cell.

Ques: Where does meiosis occur?

Ans: Meiosis happens during gametogenesis. It takes place in reproductive cells and germ cells. It occurs in germ cells as they need to grow and develop complex organ structures of it's parents that results in cell division 

Ques: During nuclear divisions like mitosis, what happens to the DNA of plastids and mitochondria?

Ans: Chloroplasts and mitochondria carry extrachromosomal DNA and do not participate in nuclear division. Mitosis involves just nuclear DNA.

Ques: At what point during meiosis does genetic material cross over?

Ans: Pachytene is the stage of meiosis during which genetic material is crossed across. During the phase, there is chromosome exchange between maternal and paternal homologous chromosomes by crossing over.

Ques: Which cell division is concerned with cancer?

Ans: Cancer is concerned with mitosis, a type of cell division.The uncontrolled division of cells allows tumors to grow and spread cancer.

Ques: Define kinetochores.

Ans: The centromeres' surface has a small disc-shaped structure called a kinetochore.During mitosis and meiosis,Kinetochores link the chromosome to microtubule polymers from the mitotic spindle.

Ques: Define interkinesis.

Ans: Interkinesis is termed as the stage between two meiotic divisions. DNA replication doesn't occur during interkinesis. Many organisms do not have the interkinesis process. 

Ques: What stains are used for coloring chromosomes?

Ans: To colour chromosomes, stains such as Gentian violet, Giemsa stain, and Safranin are often used.

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Short Answer Questions [2 Marks Question]

Ques: Apart from spindle formation, what role do centrioles play?

Ans: The two centrioles in the centrosome are arranged in a cartwheel pattern, perpendicular to each other. They form the basal body of cilia and flagella of animal/plant cells, in addition to the spindle fibre development seen in animal cell division. They also aid in the development of microtubules and the sperm tail.

Ques: Mitotic division is the division of a cell with 32 chromosomes. What will the cell's chromosomal number (N) be during metaphase? What will the cell's DNA content be during anaphase?

Ans: The somatic cells of entities undergo mitosis. Both the parent and daughter cells have the same number of chromosomes, which does not vary during anaphase or metaphase. During the interphase or synthetic phase, however, the amount of DNA doubles. The division occurs during anaphase, although the number of chromosomes does not alter.

Ques: Meiosis occurs in which tissues of animals and plants?

Ans: Only the tissues that create gametes go through meiosis. Meiosis occurs in animals within the reproductive cells or germ cells of the body, which includes the testes and ovaries. The Androecium (male reproductive) and Gynoecium (female reproductive) portions of the plant undergo meiosis.

Ques: If the average duplication time of E. Coli cells is 20 minutes, how long will it take two E. Coli cells to become 32 cells?

Ans: It will take 1 hour and 20 minutes to complete. There are four subsequent cell divisions, each of which produces 16 cells and takes a total of 20 minutes. As a result, the total time is equal to 20 x 4 = 80 minutes, or one hour and twenty minutes. As a result, one cell can produce 16 cells in 80 minutes and two cells can produce 32 cells in 1 hour and 20 minutes.

Ques: Why is meiosis referred to as reductional division, whereas mitosis is referred to as equational division?

Ans: The number of chromosomes is reduced to half during meiosis, which is known as reductional division. In sexually reproducing species, gametes are generated in the germ cell. The number of chromosomes in mitosis remains constant after division, therefore it is referred to as equational division.

Ques: What role does chromosomal replication play during interphase?

Ans: Interphase is a period of time between cell divisions. It is regarded as the resting stage of a nucleus since it shows no morphological changes; but, physiologically, it is an active stage in the life of a cell as the cell prepares for division and other biochemical changes.

Ques: What effect does duration have on an organism's cell cycle?

Ans: The length of time depends on the cell type as well as external elements including temperature, food, and oxygen. In different species, the G, S, G, and M phases take different time, for example 20 minutes for bacterial cells, 10 hours for intestinal epithelial cells, 20 hours for onion root tip cells, and so on, depending on the environmental conditions. This demonstrates that the time required for each phase has been pre-programmed into each organism's cells.

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Short Answer Questions [3 Marks Question]

Ques: Explain Synaptonemal complex and Metaphase plate

Ans: Synaptonemal Complex: These are zipped structures that form between homologous chromosomes during the prophase of first meiosis. The continual rearrangements of chromatin throughout the meiotic prophase, such as pouring, recombination, condensation, and homologous chromosome malfunction, are linked to this disassembly and assembly. The quantity and distribution of reciprocal exchanges between homologous chromosomes are controlled by these. They transform into functional chiasmata as they cross over.

Metaphase plate: In metaphase, the centromeres of the chromosomes congregate on the metaphase plate, which is an imaginary line that runs parallel to the two centrosome poles. The opposite kinetochore microtubules are responsible for the alignment. The sister chromatids, in particular, are related to the package of four to eight spindle fibres on this plate.

Ques: What is P-oxidation?

Ans: During digestion, fats are broken down into glycerol and fatty acids. At the triose phosphate stage, glycerol enters the glycolytic pathway. Fatty acids are oxidized when two-carbon fragments of acetyl A are split off from the fatty acid chain at a time, shortening the long fatty acid molecule by two carbon atoms at a time. This leads to fatty acid oxidation that is incomplete.

Ques: Explain telophase as the reverse of prophase.

Ans: Prophase begins with the condensation of chromosomal material. The chromosomal material untangles during the chromatin condensation process. When the chromosomes reach the respective poles during the final stage of mitosis, telophase, they de-condense and lose their individuality. 

The cells at the end of prophase lack Golgi complexes, nucleolus, endoplasmic reticulum and the nuclear envelope, when examined under a microscope. At the telephone stage, the nuclear envelope gathers around the chromosome cluster. The nucleolus reform, the Golgi complex, and the ER.

Ques: Define homologous chromosomes? During meiosis, what happens to homologous chromosomes?

Ans: Homologous chromosomes are defined as pairs of chromosomes that share genes that control the same set of traits.

The chromosomes in leptotene are thread-shaped and coiled during the heterotypic division of meiosis. Homologous chromosomes begin to pair during zygotene. Chromosomes thicken while also shortening in pachytene. The absence of attraction force between the two homologous chromosomes characterizes diplotene. The uncoiling of homologous chromosomes separates them, but they remain attached to the chiasmata. The homologous chromosome is completely separated during diakinesis.

It is possible for parts to be exchanged between chromatids of homologous chromosomes. Following the separation of the centromere, centromeres of homologous bivalent compounds repel each other during Anaphase I. In telophase-I, homologous chromosomes begin to move apart, and chromosomes reach poles and shorten.

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Long Answer Questions [5 Marks Question]

Ques: What is the significance of meiosis?

Ans: The process by which sexually reproducing organisms produce their sex cells, sperm, and eggs is known as meiosis. A specialised cell known as a germ cell splits into four new sex cells during meiosis, each with half the number of chromosomes as the original germ cell.

The significance of meiosis is as mentioned below - 

• Meiosis is responsible for the formation of gametes, which are necessary for sexual reproduction.
• Meiosis is the process by which genetic information is switched on for the development of gametes.
• Chromosome number maintenance In sexually reproducing organisms, meiosis keeps the number of chromosomes constant.
• Chromosome Assortment- In meiosis, paternal and maternal chromosomes assort separately. It causes reshuffling of chromosomes and the traits controlled by them.
• It introduces new combinations of traits or variations by crossing over.
• Mutations occur as a result of irregularities in the meiotic division.

Ques: Describe the steps involved in aerobic glycolysis.

Ans: The conversion of glucose to pyruvic acid is known as glycolysis, and it includes the steps mentioned below.

• Phosphorylation is the process of transferring phosphate from ATP to glucose, resulting in glucose – 6 phosphate. Hexokinase, an enzyme that consumes one molecule of ATP, is present.
• Isomerisation, Internal molecular rearrangement occurs, resulting in fructose 6 phosphates. Hexose phosphate isomerase is the enzyme.
• The fructose – 6-phosphate is phosphorylated a second time to produce fructose 1,6 diphosphate. One ATP molecule is used up. Phosphofructokinase is the enzyme in question.
• 3-phosphoglyceraldehyde (PGAL) and dihydroxyacetone phosphate are triose phosphates (DHAP). The enzyme phosphorised isomerase maintains the balance between the two isomers.
• Phosphorylation and oxidative dehydrogenation, To generate 1,3 diphosphoglyceric acid, PGAL undergoes simultaneous phosphorylation and oxidative dehydrogenation.
• ATP production, 1,3 diphosphoglyceric acid forms ATP and 3-phosphoric acid by transferring its phosphate to ADP via a high-energy link. One molecule of triose yields one molecule of ATP.

Ques: What are the different phases of meiosis II division?

Ans: The following are the stages of meiosis II.

• Prophase II: Meiosis II begins soon after cytokinesis, usually before the chromosomes have fully extended. The chromosomes condense followed by the dissolution of the nuclear membrane and disappearance of the Golgi apparatus and ER complex.
• Metaphase II-The chromosomes align at the equator during this stage. Chromosomes are connected to centriole poles at the kinetochores of sister chromatids with the help of microtubules.
• Anaphase-II begins with the centromeres of each chromosome splitting at the same time, allowing them to move to opposite poles of the cell.
• Telophase-II: Meiosis comes to an end with telophase-II, in which two groups of chromosomes are once again encased by the nuclear envelope, followed by cytokinesis, which results in the formation of four haploid daughter cells.

Ques: Differentiate between mitosis and meiosis.

Ans: The differences between mitosis and meiosis are:

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