Cell Cycle and Cell Division MCQ Quiz in मल्याळम - Objective Question with Answer for Cell Cycle and Cell Division - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

Concept:

• Chromosomes are rod-shaped, dark-stained bodies that can be seen under a light microscope during the metaphase stage of cell division.
• Chromosomes contain DNA in a highly coiled state.
• They carry genetic information in the form of genes and play an important role in heredity.
• The number of chromosomes present in an organism is constant for a particular species.
• Along with the chromosome number, the size and shape of individual chromosomes are also constant for a particular species.

Important Points​

• Chromosomes are visible under a microscope during the metaphase stage of cell division.
• During the metaphase stage of the cell division, chromosome condensation is completed and thus can be observed clearly under the light microscope.
• In the metaphase stage of the cell division, the following structural features of a chromosome can be observed under the light microscope:

1. Chromatid
2. Chromonema
3. Chromomeres
4. Centromere
5. Nucleolar organizer
6. Telomere
7. Satellite

• At the metaphase stage, a chromosome is made up of two sister chromatids.
• The two sister chromatids are held together by the centromere.
• The chromosomes at the metaphase stage lie at the equatorial plane with one chromatid connected by its kinetochore to spindle fibers at one pole.
• Whereas, the other chromatid is connected to the spindle fibers of the opposite pole by its kinetochore.

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So, the correct answer is option 1.

The correct answer is the force of repulsion between the divided kinetochores

Explanation:

• A kinetochore is a plate-like structure by which microtubules of the spindle attach to the centromere of a chromosome during nuclear division.
• The centromere of each chromosome divides into two, so that each chromatid comes to have its own centromere. The two chromatids now start repelling each other and separate completely to become daughter chromosomes.
• The daughter or new chromosomes move towards the poles of spindle along the path of their chromosomes fibres or tractile fibrils.

Concept: 

• Meiosis is defined as a specialized form of cell division that produces reproductive cells, such as plant and fungal spores and sperm and egg cells.
• In meiosis, the number of chromosomes reduces in the parent cell by half and produces four gamete cells.

​​Explanation:

Option 1: 

• After meiosis I, the resultant daughter cells have twice the amount of DNA in comparison to haploid gametes.
• Therefore, this is the incorrect option.

Option 2: ​

• After meiosis I, the resultant daughter cells have twice the amount of DNA in comparison to haploid gametes.
• Therefore, this is the incorrect option.

Option 3: ​

• In the S phase (Synthesis Phase) DNA is replicated, occurring between the G₁ phase and the G₂ phase.
• Since accurate duplication of the genome is critical to successful cell division, the processes that occur during S-phase are tightly regulated and widely conserved.
• Therefore, this is the incorrect option.

Option 4: ​

• Meiosis produces four daughter cells from one single parent cell. Each daughter cell is haploid because it has half the number of chromosomes as the original parent cell. Haploid cells have a single set of chromosomes or DNA.
• By the end of meiosis I, the resulting reproductive cells have half the number of chromosomes with duplicate DNA in the form of sister chromatids.
• These reproductive cells again undergo meiosis II to form haploid gametes having a single set of DNA. Hence, after meiosis I, the resultant daughter cells have twice the amount of DNA in comparison to haploid gametes.
• Therefore, this is the correct option.

So, the correct answer is option 4.

The correct answer is Anaphase - II

Explanation:

Meiosis is a specialized type of cell division that reduces the chromosome number by half, resulting in four haploid cells. It consists of two successive divisions: meiosis I and meiosis II.

• Meiosis I
  • Prophase I: Homologous chromosomes pair up and exchange segments in a process called crossing over.
  • Metaphase I: Paired homologous chromosomes align along the metaphase plate.
  • Anaphase I: Homologous chromosomes separate and move to opposite poles. 
  • Telophase I and Cytokinesis: The cell divides into two haploid cells with duplicated chromosomes (each chromosome still consists of two sister chromatids).
• Meiosis II (Similar to mitosis, but without chromosome replication)
  • Prophase II: Chromosomes condense, spindle apparatus forms in each new cell.
  • Metaphase II: Chromosomes align at the metaphase plate in each cell.
  • Anaphase II: The centromeres split, and sister chromatids (now individual chromosomes) are pulled to opposite poles of each cell.
  • Telophase II and Cytokinesis: Nuclear membranes reform around the chromosomes, and the cells divide, resulting in four haploid daughter cells.
• During Anaphase II, the sister chromatids are finally separated at the centromere and are pulled to opposite spindle poles in each of the two cells produced by meiosis I.
• By the end of Anaphase II, each cell has a complete set of individual chromosomes (formerly sister chromatids) positioned at opposite poles. This sets the stage for the completion of cell division in Telophase II.

The correct answer is E.coli

Explanation:

Mitosis is a type of cell division that occurs in eukaryotic cells, which includes stages such as prophase, metaphase, anaphase, and telophase. These stages ensure that the replicated chromosomes are equally distributed to the two daughter cells.

• E.coli is a bacterium (prokaryote). E.coli divides through a process called binary fission, which is simpler and does not involve the complex stages of mitosis.
  • In binary fission, the bacterial chromosome is replicated, and the cell grows until it can divide into two new cells.
  • The DNA is directly attached to the cell membrane, and as the cell grows, the two copies of the chromosome are separated without the need for a spindle apparatus or other mitotic structures.

Other options:

• Cosmarium: Eukaryotic green alga. Cosmarium undergoes mitosis to divide its cells.
• Saccharomyces (Yeast): Eukaryotic fungus. Yeast cells undergo mitosis during asexual reproduction.
• Chlorella: Eukaryotic green alga. Chlorella undergoes mitosis to divide its cells.

The correct answer is Metaphase.

Explanation:

• Spindle fibers attach to the kinetochores of chromosomes during the process of cell division. This attachment is crucial for proper alignment and separation of chromosomes. The specific phase during which spindle fibers connect to kinetochores is Metaphase
• During metaphase, chromosomes align at the cell's equatorial plate, and the spindle fibers attach to the kinetochores of the sister chromatids, which allows for their subsequent segregation into the daughter cells during anaphase.

• At the metaphase stage, a chromosome is made up of two sister chromatids.
• The two sister chromatids are held together by the centromere.
• The chromosomes at the metaphase stage lie at the equatorial plane with one chromatid connected by its kinetochore to spindle fibers at one pole.
• Whereas, the other chromatid is connected to the spindle fibers of the opposite pole by its kinetochore.

The correct answer is Four chromatids and two centromeres

Concept:

• Cell division refers to the sequential events that lead to the parent cell dividing into two or more cells called daughter cells.
• There are two types of cell division- mitosis and meiosis.
• Mitosis is the vegetative division in which each daughter cell duplicates the parent cell.
• Meiosis is the reduction division in which the parent cell divides into four haploid daughter cells.
• Mitosis is observed in almost all somatic cells, while meiosis takes place only in germ cells.
• Meiosis divides into two types meiosis I and meiosis II.

Explanation:

During meiosis I, homologous chromosomes pair up and form structures called bivalents (also known as tetrads). 

• Homologous Chromosomes: Each bivalent is made up of two homologous chromosomes. Each chromosome has already replicated during the S phase prior to meiosis I, so it consists of two sister chromatids.
• Chromatids: Since each homologous chromosome has two sister chromatids, the bivalent includes a total of four chromatids (2 chromatids per homologous chromosome).
• Centromeres: Each chromosome has one centromere, so a pair of homologous chromosomes (or a bivalent) will have two centromeres in total.

The correct answer is Nuclear membrane.

• The nuclear envelope, also known as the nuclear membrane, is made up of two lipid bilayer membranes that in eukaryotic cells surrounds the nucleus, which encloses the genetic material.

Key Points

• ​The nuclear envelope is also called nuclear membrane. It is made up of two lipid bilayer membranes.
• The nuclear membrane is present in both the plant and animal cells.
• Cells carry out a multitude of functions such as protein building, conversion of molecules into energy and elimination of unnecessary products.
• This membrane guards the genetic material of the cells against the exterior of the nucleus where chemical reactions are taking place.
• Also, it carries several proteins which are crucial in the organization of DNA  and to control genes.​

Additional Information

• The plasma membrane forms the physical barrier between the cytoplasm and extracellular space, allowing for biochemical reactions necessary for life to occur
• Ribosomes, also called Palade granules, are macromolecular machines, found within all cells, that perform biological protein synthesis.
• The cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus.

​

Concept:

• Cell cycle refers to the series of changes that take place in a newly formed cell involving its growth and division.
• Cell division gives rise to new daughter cells.
• The cell cycle comprises two stages -  The M phase and the Interphase.
• The M Phase represents the phase when the actual cell division or mitosis occurs. It is a short dividing phase.
• Interphase represents the phase between two successive M phases. It is a long non-dividing growing phase.

Important Points

Interphase:

• Interphase generally can be divided into the following steps:  Gap 1 (G₁), S (synthesis) phase and Gap 2 (G₂).
• During the G₁ phase, the cell is metabolically active and continuously grows but does not replicate its DNA.
• This is followed by S or the synthesis phase. This phase marks the period during which DNA synthesis or replication takes place.
• Next during the G₂ phase, proteins are synthesized in preparation for mitosis while cell growth continues. 
• The interphase stage is followed by the M phase where the cells undergo cell division. This phase gives rise to new daughter cells.

​

• Thus from the above-given information, the regular sequence of the cell cycle is G1, S, G2, M.

Mitotic Phase (M Phase):

The mitotic phase includes mitosis and cytokinesis and is responsible for cell division.
Mitosis: Mitosis is the process by which the nucleus of the cell divides, resulting in the formation of two daughter nuclei that are genetically identical to the parent nucleus. Mitosis is further divided into several stages:

• Prophase: Chromatin condenses into visible chromosomes, and the nuclear envelope breaks down.
• Metaphase: Chromosomes align at the cell's equatorial plane (metaphase plate).
• Anaphase: Sister chromatids separate and move toward opposite poles of the cell.
• Telophase: Chromosomes decondense, and nuclear envelopes reform around the separated chromatids.

So the correct answer is option 3 (G1, S, G2, M).

 Additional Information

• Cells that do not divide further exit the G₁ phase to enter an inactive stage called the 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.

The correct answer is Animal cells form a furrow, while plant cells form a cell plate.

Explanation:

• Cell plate formation occurs during cytokinesis in plant cells. As the plant cell divides, a new cell membrane and cell wall are synthesized between the two daughter cells, creating a cell plate that eventually matures into the new cell wall. This process partitions the cytoplasm and separates the two daughter cells.

• In contrast, cleavage furrow formation occurs during cytokinesis in animal cells. As the animal cell divides, an indentation or "cleavage furrow" forms in the cell membrane, gradually deepening until the cell is pinched in two, splitting the cytoplasm and creating two daughter cells. Cleavage furrows are driven by the contraction of an actin-myosin ring around the equator of the dividing cell.

• Cell plate appears in the centre and grows outwards (centrifugal) by deposition of phragmoplast (vesicles) but cleavage furrow appears from the cell membrane and grows inwards (centripetal).