Cell Cycle and Cell Division MCQ Quiz - Objective Question with Answer for Cell Cycle and Cell Division - Download Free PDF

The correct answer is To separate the chromosomes

Explanation:

• Mitosis is the process of cell division in eukaryotic cells that results in two genetically identical daughter cells. This process is crucial for growth, repair, and asexual reproduction in multicellular organisms.
• Spindle fibers are protein structures formed during cell division. They originate from the centrosomes (or spindle pole bodies in some organisms) and play a critical role in ensuring the chromosomes are properly aligned and separated.
• The spindle fibers attach to the centromeres of the chromosomes through structures called kinetochores. This attachment is essential for the correct segregation of chromosomes during mitosis.
• During metaphase, spindle fibers align the chromosomes along the metaphase plate (the center of the cell). This ensures that each daughter cell will receive an identical set of chromosomes.
• In anaphase, spindle fibers pull the sister chromatids apart by shortening, ensuring that one copy of each chromosome moves to opposite poles of the cell. This separation is important for maintaining the correct chromosome number in daughter cells.

The correct answer is a - 3, b - 2, c - 4, d - 1

Explanation:

• Zygotene: 
  • Zygotene is the second stage in the Prophase-I of Meiosis that takes place after the completion of the leptotene.
  • Zygotene is distinguished by the synapsis, or pairing, of homologous chromosomes to form a bivalent chromosome.
  • In this phase, Homologous chromosomes pair up. This pairing is done in such a way that the genes for the same character on both chromosomes are exactly opposite to each other. This association process is known as synapsis.

• Anaphase: Anaphase is characterized by the splitting of the centromere, which allows the chromatids (or chromosomes during Anaphase I and II of meiosis) to move toward opposite poles.

• Pachytene: 

  • This is the stage immediately following zygotene in which the chromosomes become twisted spirally around each other and cannot be distinguished separately.
  • Crossing-over occurs during meiosis at the pachytene stage when homologous chromosomes are completely paired.
• Metaphase: During Metaphase, chromosomes align at the spindle equator to ensure that each new cell will receive one copy of each chromosome.

The correct answer is The formation of synaptonemal complex is seen during diakinesis stage

Explanation:

Leptotene, Zygotene, Pachytene, Diplotene and Diakinesis are the various stage of Prophase I is the longest stage of the meiotic division.

• Leptotene: The chromosomes begin to condense and become visible under a microscope. Compaction of chromosomes continues throughout this phase. 
• Zygotene: Homologous chromosomes pair up through a process called synapsis, and the formation of the synaptonemal complex begins. (Statement 1 is incorrect because the synaptonemal complex formation occurs during zygotene, not diakinesis)
• Pachytene: Crossing over, the exchange of genetic material between homologous chromosomes, occurs during this phase.
• Diplotene: The synaptonemal complex disintegrates, and the homologous chromosomes begin to separate but remain connected at chiasmata, where crossing over occurred.
• Diakinesis: The final phase of prophase I, where the chromosomes are fully condensed and the chiasmata move towards the ends of the chromosomes (terminalisation). 

Therefore, the incorrect statement is the formation of synaptonemal complex is seen during diakinesis stage.

Additional Information 

The correct answer is Homologous chromosomes separate in Anaphase I but Centromeres split in Anaphase II

Explanation:

• Anaphase I: During Anaphase I of meiosis, homologous chromosomes are pulled apart to opposite poles of the cell. Sister chromatids remain associated at their centromeres.The centromeres do not split during this stage; instead, the entire chromosome (consisting of two sister chromatids) is moved to opposite poles. (Homologous chromosomes separate)
• Anaphase II: During Anaphase II of meiosis, the centromeres split, and the sister chromatids (which were previously part of the same chromosome) are pulled apart to opposite poles of the cell. (Centromeres split)

Therefore, Anaphase I is characterized by the separation of homologous chromosomes, while Anaphase II is characterized by the splitting of centromeres, which allows the sister chromatids to separate.

The correct answer is a- iv, b- iii, c- ii, d- i

Explanation:

• Prophase: During prophase, chromosomes are seen to be composed of two chromatids attached together at the centromere. 
• Metaphase: During metaphase, spindle fibers attach to kinetochores of chromosomes and align the chromosomes at the metaphase plate. 
• Anaphase: During anaphase, centromeres split and chromatids separate, with each chromatid moving towards opposite poles of the cell. 
• Telophase: During telophase, chromosomes cluster at opposite spindle poles and the cell prepares to divide into two daughter cells. 

The correct answer is i - b, ii - a, iii - c, iv - d

Key Points

• The cell physically expands, duplicates organelles, and creates the molecular building blocks it will require in subsequent stages during G1phase, also known as the first gap phase.
• The cell creates a full copy of the DNA in its nucleus during the S phase. Moreover, it makes duplicates of the centrosome, a structure that organises microtubules. During M phase, the centrosomes aid in the separation of DNA.
• The second gap phase, also known as the G2 phase, is a time of increased cell growth, protein and organelle production, and content reorganisation in preparation for mitosis.
• The cell's nuclear DNA condenses into its visible chromosomes during mitosis and is separated by the mitotic spindle, a specialised microtubule-based structure.

Additional Information

•  Stages of the cell cycle
  • ​A cell must grow, replicate its genetic material (DNA), and physically split into two daughter cells before it may divide.
  • The cell cycle is a structured, predictable series of actions that cells take to complete these goals.
  • Because the two daughter cells can restart the entire process from the beginning after each cycle, the cell cycle is a cycle rather than a linear pathway.

Concept-

• Mitotic produced genetically identical cells, which are similar to the mother cells.
• Mitotic is also called equational division.
• Mitotic cell division is divided into the following four stages-
  • (a) Prophase  (b) Metaphase  (c) Anaphase  (d) Telophase

Explanation-

• At the beginning of the final stage of mitosis, i.e., telophase, the chromosomes that have reached their respective poles decondense and lose their individuality.
• The individual chromosomes can no longer be seen and chromatin material tends to collect in a mass in the two poles.
• This is the stage which shows the following key events-
  • Chromosomes cluster at opposite spindle poles and their identity is lost as discrete elements.

Hence in telophase, chromosome lost their identity.

Additional Information

• Mitosis or the equational division is usually restricted to the diploid cells only.
• Mitosis usually results in the production of diploid daughter cells with identical genetic complement.
• The growth of multicellular organisms is due to mitosis.
• A very significant contribution to mitosis is cell repair.

Concept:

• Cell cycle refers to the series of changes that occur in a newly formed cell. It involves a cell's growth and division to form two daughter cells.

• The cell cycle comprises two stages - the Interphase and M phase.
• 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.
• Interphase can be divided into 4 steps: Gap 1 (G1), S (synthesis) phase, and Gap 2 (G2).

Important Points

• G₁ Phase - 
  • In a human cell, the G1  phase of the cell cycle lasts for approximately 11-12 hours.
  • During the G1 phase, the cell is metabolically active and continuously grows but does not replicate its DNA.
• S Phase - 
  • In a human cell, the S phase of the cell cycle lasts for about 8 hours.
  • S or synthesis phase marks the period during which DNA synthesis or replication takes place.
• G₂ Phase - 
  • The G2  phase of the cell cycle lasts for about 4 hours.
  • During the G2 phase, proteins are synthesized in preparation for mitosis while cell growth continues. 
• M Phase
  • The M phase of the cell cycle lasts for about 1 hour in a human cell.
  • It is the phase of the cell cycle where cell division takes place.
• The​ cell cycle in a human cell comprising of the Interphase and M phase lasts for a total time of 24 hours.

So the correct answer is option 1 (24 hours).

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.

​

The correct answer is Number of chromosomes remains the same in Mitosis.Key Points

• The number of chromosomes remains the same in Mitosis is TRUE about the process of Mitosis.

 Mitosis:

• It is a process where a single cell divides into two identical daughter cells (cell division).
• The major purpose of mitosis is for growth and to replace worn-out cells.
• In cell biology, mitosis is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei.
• Mitosis has four sequential stages:
  • Prophase.
  • Metaphase.
  • Anaphase.
  • Telophase.
• ​​Cytokinesis is the final physical cell division that follows telophase.

Additional Information

The correct answer is Chloroplasts are found only in plant cells, but not in animal cells 

Key PointsThe chloroplast

• The chloroplast is an organelle that contains the photosynthetic pigment chlorophyll that captures sunlight and converts it into useful energy, thereby, releasing oxygen from water. 
• Chloroplasts are found in all green plants and algae. Hence,Statement 3 is wrong
• They are the food producers of plants.
• These are found in the guard cells located in the leaves of the plants.
• They contain a high concentration of chlorophyll that traps sunlight.
• This cell organelle is not present in animal cells.

Explanation-

• RuBP enzyme is required for Photosynthesis.
• RuBP enzyme is the most abundant enzyme present in plants.
• It catalyzes the carboxylation reaction between carbon dioxide and Ribulose Bisphosphate.
• It is used in the Calvin cycle of Photosynthesis.
• Each molecule of carbon dioxide is attached to a five-carbon sugar called ribulose bisphosphate (RuBP).
• Rubisco is the most abundant protein found in chloroplasts.

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.

 ​

So, the correct answer is option 1.

Concept:

• Cell division is of three types:

1. Mitosis - Equational division, occurs in somatic (non-sex) cells
2. Meiosis - Reductional division, occurs in sex cells
3. Amitosis - Direct type of division, occurs in prokaryotes

• Meiosis is the division in which the parent cell divides to form four daughter cells.
• Meiosis can be further divided into two stages - Meiosis I and Meiosis II 
• Prophase I of Meiosis I has 5 sub-stages
• Leptotene, Zygotene, Pachytene, Diplotene, Diakinesis.

Explanation:

• Crossing over refers to the exchange of genetic material between the non-sister chromatids of homologous chromosomes
• Crossing over is also known as recombination
• It occurs in the pachytene stage of meiosis I 
• Crossing over is governed by the enzyme recombinase.

                                                  Diagram showing Crossing over 

Concept:

• Meiosis is the type of cell division that reduces the chromosome number by half resulting in the production of haploid daughter cells.
• Meiosis ensures the production of the haploid phase in the life cycle of sexually reproducing animals whereas fertilization restores the diploid phase.
• It takes place in the germ cells.
• Meiosis comes across during gametogenesis in plants and animals and leads to the formation of haploid gametes.
• Meiosis results in variations among the offspring, as maternal and paternal genes, get exchanged during crossing over.
• This cell division involves two sequential cycles of nuclear and cell division called meiosis I and meiosis II but only a single cycle of DNA replication.
• Meiotic events can be classified into the following phases-

• Meiosis I is initiated after the parental chromosomes have replicated to produce identical sister chromatids at the S phase.
• While meiosis II is initiated immediately after cytokinesis, usually before the chromosomes have fully elongated.
• Four haploid cells are formed at the end of meiosis.

Important Points

• Among the given meiotic events, the correct sequence is - 
  1. Procentric pairing of chromosomes
  2. Terminalisation of chiasmata
  3. Arrangement of bivalents in the plane of the equator of the cell
  4. Splitting of centromere and separation of sister chromatids
• During the zygotene stage of prophase I, chromosomes start pairing and this process of association is called synapsis.
• These paired chromosomes are called homologous chromosomes.
• Diakinesis is the final stage of meiotic prophase I and is marked by the terminalisation of chiasmata.
• Chiasmata is the contact point between two non-sister chromatids belonging to homologous chromosomes.
• These are X-shaped structures visible in the diplotene stage of prophase I.
• During metaphase I, the bivalent chromosomes are aligned in the plane of the equator of the cell.
• The microtubules from the opposite poles of the spindle attach to the pair of homologous chromosomes in the metaphase I.
• The anaphase II phase begins with the splitting of the centromere and the separation of sister chromatids.
• This allows sister chromatids to move toward opposite poles of the cells.

Hence, the correct answer is option 1 - (iii), (ii), (iv), (i).