101. Which statement about chromosome number in mitosis is correct?
ⓐ. It becomes doubled permanently in each daughter cell
ⓑ. It becomes half in one daughter cell and full in the other
ⓒ. It remains the same as that of the parent cell
ⓓ. It changes randomly depending on the tissue
Correct Answer: It remains the same as that of the parent cell
Explanation: One of the defining features of mitosis is that chromosome number is maintained from parent cell to daughter cells. The chromosomes are distributed equally during division so that each daughter nucleus receives the same complement. This constancy is essential for preserving normal body functions and tissue identity. If chromosome number changed randomly, stable growth and maintenance would not be possible. Because mitosis is equational, it ensures chromosomal continuity across cell generations. Therefore, the chromosome number remains the same as that of the parent cell.
102. Replacement of worn-out cells in tissues such as skin is mainly achieved by:
ⓐ. synapsis and crossing over
ⓑ. mitotic cell division
ⓒ. reductional division
ⓓ. chromosome pairing
Correct Answer: mitotic cell division
Explanation: Many tissues of the body lose cells regularly and must replace them to remain functional. Mitosis provides this replacement by forming new cells of the same general type as those that were lost. Because the daughter cells retain the same chromosome number and similar genetic makeup, tissue continuity is preserved. This makes mitosis essential in renewing surface and lining tissues. The process therefore helps maintain the normal structure and function of such tissues over time. Hence, replacement of worn-out cells is mainly achieved by mitotic cell division.
103. The occurrence of mitosis in unicellular eukaryotes mainly helps in:
ⓐ. producing chromosomal variation through pairing
ⓑ. maintaining the cell in a permanent $G_0$ stage
ⓒ. converting the nucleus into cytoplasm
ⓓ. asexual reproduction and increase in number
Correct Answer: asexual reproduction and increase in number
Explanation: In unicellular eukaryotes, one cell itself represents the entire organism, so mitotic division directly increases the number of individuals. This makes mitosis a means of asexual reproduction in such organisms. Since the daughter cells receive similar genetic information, the process produces new individuals efficiently while maintaining continuity. This role is different from its function in multicellular organisms, where mitosis mainly supports growth and repair. The principle of equal nuclear division, however, remains the same. Therefore, in unicellular eukaryotes, mitosis mainly helps in asexual reproduction and increase in number.
104. Which statement best summarizes the overall role of mitosis in multicellular organisms?
ⓐ. It mainly creates new gene combinations for variation
ⓑ. It supports growth, cell replacement, and maintenance of tissues
ⓒ. It reduces chromosome number before fusion of gametes
ⓓ. It produces four haploid cells from one parent cell
Correct Answer: It supports growth, cell replacement, and maintenance of tissues
Explanation: Mitosis is essential in multicellular organisms because it provides new cells wherever the body needs them. During growth, it increases cell number; during tissue maintenance, it replaces worn-out cells; and during repair, it restores damaged areas. Because the chromosome number remains unchanged, the newly formed cells can continue the same functions as the original tissue cells. This makes mitosis a process of continuity and stability. Its overall biological role is therefore strongly tied to normal body development and upkeep. Hence, the best summary is that mitosis supports growth, cell replacement, and maintenance of tissues.
105. A child’s height increases over time mainly because many body cells repeatedly undergo mitosis, which:
ⓐ. halves the chromosome number in growing tissues
ⓑ. adds new cells while maintaining cellular continuity
ⓒ. produces gametes needed for body enlargement
ⓓ. creates variation through chromosome pairing
Correct Answer: adds new cells while maintaining cellular continuity
Explanation: Growth in a child depends on an increase in the number of body cells, and mitosis provides that increase in an orderly way. During mitosis, new daughter cells are formed without changing the chromosome number of the parent cell. This helps tissues enlarge while preserving their basic cellular nature. Because the new cells remain similar to the original ones, normal structure and function can be maintained during growth. The process therefore supports increase in body size without disturbing tissue identity. That is why mitosis adds new cells while maintaining cellular continuity.
106. Which situation is the best example of the normal role of mitosis in tissue maintenance?
ⓐ. formation of sperm cells in the testes
ⓑ. pairing of homologous chromosomes in a nucleus
ⓒ. replacement of worn-out lining cells in the intestine
ⓓ. reduction of chromosome number before fertilization
Correct Answer: replacement of worn-out lining cells in the intestine
Explanation: Tissue maintenance requires old, damaged, or worn-out cells to be replaced by new cells of the same kind. Mitosis is the process that makes this possible in ordinary body tissues. The intestinal lining is a good example because its cells are frequently lost and must be renewed continuously. Since mitosis preserves chromosome number and general cellular identity, it is well suited for such replacement. The process is therefore directly related to maintaining tissue integrity. This makes replacement of worn-out intestinal lining cells the best example of the normal role of mitosis.
107. Assertion (A): Mitosis is suitable for growth and repair in multicellular organisms.
Reason (R): Mitosis generally produces daughter cells that retain the parental chromosome number.
ⓐ. Both A and R are true, and R is the correct explanation of A.
ⓑ. Both A and R are true, but R is not the correct explanation of A.
ⓒ. A is true, but R is false.
ⓓ. A is false, but R is true.
Correct Answer: Both A and R are true, and R is the correct explanation of A.
Explanation: The assertion is correct because growth and repair require new cells that can function like the original cells of the tissue. The reason is also true because mitosis maintains the chromosome number from parent cell to daughter cells. This chromosomal continuity helps preserve the general genetic constitution of the tissue. As a result, the daughter cells are suitable for replacing lost cells and contributing to growth. The reason therefore directly explains why mitosis is appropriate for these biological roles. Hence, both statements are true and the reason correctly explains the assertion.
108. A student says, “Mitosis is useful only during early growth and has no role in adult organisms.” Which response is most accurate?
ⓐ. The statement is correct because adults no longer form new somatic cells
ⓑ. The statement is correct because mitosis is limited to embryonic tissues
ⓒ. The statement is wrong because adult tissues also use mitosis for renewal and repair
ⓓ. The statement is wrong because mitosis occurs only in reproductive organs
Correct Answer: The statement is wrong because adult tissues also use mitosis for renewal and repair
Explanation: Mitosis is not restricted to early developmental stages. In adult organisms, many tissues still require new cells to replace worn-out ones and to repair damage after injury. This ongoing renewal depends on mitotic division in appropriate cell populations. Since mitosis maintains tissue continuity, it remains important even after growth slows. Its role in adults is therefore closely linked with maintenance and healing rather than only body enlargement. For that reason, the correct response is that adult tissues also use mitosis for renewal and repair.
109. Which of the following is a non-example of the primary biological role of mitosis?
ⓐ. healing of a cut surface by formation of similar cells
ⓑ. increase in cell number during normal body growth
ⓒ. renewal of cells lost from a tissue surface
ⓓ. production of haploid gametes for sexual reproduction
Correct Answer: production of haploid gametes for sexual reproduction
Explanation: The primary roles of mitosis include growth, tissue maintenance, and repair through the production of similar daughter cells. These functions depend on preservation of chromosome number and continuity of tissue identity. Production of haploid gametes is different because it involves reduction in chromosome number for sexual reproduction. That outcome does not represent the main biological purpose of mitosis in the body. Therefore, it stands apart from the usual roles of mitotic division. This makes production of haploid gametes the non-example here.
110. In a unicellular eukaryote, mitosis is especially important because it directly:
ⓐ. separates homologous chromosomes for variation
ⓑ. creates tissues from groups of somatic cells
ⓒ. forms new individuals by cell multiplication
ⓓ. reduces chromosome number before fusion
Correct Answer: forms new individuals by cell multiplication
Explanation: In a unicellular eukaryote, one cell itself is the whole organism, so cell division has the effect of producing another organism. Mitosis therefore functions directly in reproduction rather than only in tissue growth. Because the daughter cells receive similar genetic material, the species can multiply efficiently while maintaining continuity. This role differs from its function in multicellular organisms, where the process mainly supports growth and maintenance of tissues. The principle of equal division, however, remains the same. Hence, mitosis in unicellular eukaryotes directly forms new individuals by cell multiplication.
111. Which statement best distinguishes the role of mitosis in multicellular organisms from its role in unicellular eukaryotes?
ⓐ. In multicellular organisms it supports body growth, while in unicellular eukaryotes it can act as reproduction
ⓑ. In multicellular organisms it reduces chromosome number, while in unicellular eukaryotes it doubles it
ⓒ. In multicellular organisms it is absent, while in unicellular eukaryotes it is compulsory
ⓓ. In multicellular organisms it forms gametes, while in unicellular eukaryotes it forms tissues
Correct Answer: In multicellular organisms it supports body growth, while in unicellular eukaryotes it can act as reproduction
Explanation: The same basic process of mitosis can serve different biological purposes depending on the type of organism. In multicellular organisms, mitosis mainly adds cells for growth, replacement, and repair of tissues. In unicellular eukaryotes, division of one cell effectively produces another organism, so mitosis functions as a mode of reproduction. This difference comes from whether the dividing cell is part of a tissue or is itself the whole organism. The mechanism remains similar, but the biological outcome differs. Therefore, the best distinction is growth in multicellular organisms versus reproduction in unicellular eukaryotes.
112. A sample of tissue shows active cell loss at the surface and continuous replacement from cells below. The most suitable conclusion is that mitosis there is helping to:
ⓐ. maintain chromosome reduction across the tissue
ⓑ. preserve the tissue by replacing lost cells
ⓒ. convert ordinary cells into gamete-producing cells
ⓓ. pair homologous chromosomes before division
Correct Answer: preserve the tissue by replacing lost cells
Explanation: When cells are regularly lost from a tissue surface, the tissue can remain functional only if new cells are produced to replace them. Mitosis provides this replacement by generating cells similar to the original tissue cells. Because the chromosome number is maintained, the new cells can continue the same structural and functional role. This is a classic example of tissue maintenance rather than reproduction or chromosome reduction. The process helps keep the tissue intact despite continuous cell loss. Therefore, the best conclusion is that mitosis is preserving the tissue by replacing lost cells.
113. Prophase of mitosis is best defined as the stage in which:
ⓐ. daughter nuclei are reorganized after chromosome separation
ⓑ. chromatids move toward opposite poles of the cell
ⓒ. chromatin condenses and the cell prepares for chromosome movement
ⓓ. cytoplasm divides to form two daughter cells
Correct Answer: chromatin condenses and the cell prepares for chromosome movement
Explanation: Prophase is the first visible stage of mitosis and marks the beginning of nuclear division. During this stage, the diffuse chromatin of interphase becomes shorter, thicker, and more distinct as chromosomes. At the same time, the cell begins organizing structures needed for later chromosome movement. This preparation includes changes in the nucleus and development of the spindle apparatus. Prophase is therefore a stage of structural reorganization rather than final separation. Its key importance lies in converting the resting genetic material into clearly visible chromosomes ready for mitosis.
114. The most characteristic change in chromosomal material during prophase is:
ⓐ. condensation of chromatin into visible chromosomes
ⓑ. reduction of chromosome number to half
ⓒ. pairing of homologous chromosomes
ⓓ. separation of sister chromatids
Correct Answer: condensation of chromatin into visible chromosomes
Explanation: At the start of mitosis, chromatin does not remain in its loose, extended form. During prophase, it condenses into clearly distinguishable chromosomes that can be handled accurately during division. This condensation is important because compact chromosomes are easier to move without tangling or damage. The change makes the genetic material visible under the microscope as discrete units. It is one of the most recognizable events of early mitosis. Therefore, the characteristic chromosomal change of prophase is condensation of chromatin into visible chromosomes.
115. In prophase, each visible chromosome usually consists of:
ⓐ. one chromatid without a centromere
ⓑ. four chromatids joined in pairs
ⓒ. one DNA strand attached to spindle fibres
ⓓ. two sister chromatids joined at the centromere
Correct Answer: two sister chromatids joined at the centromere
Explanation: By the time a cell enters mitosis, DNA replication has already taken place during S phase of interphase. As a result, each chromosome seen in prophase is made up of two identical sister chromatids. These chromatids remain attached to one another at a common centromere. This structure is important because the chromatids will later separate and move to opposite poles. Thus, the prophase chromosome is not a single unreplicated thread but a duplicated structure. Therefore, each visible chromosome in prophase consists of two sister chromatids joined at the centromere.
116. The spindle apparatus begins to form mainly during:
ⓐ. interkinesis
ⓑ. prophase
ⓒ. telophase
ⓓ. cytokinesis
Correct Answer: prophase
Explanation: The spindle apparatus is essential for moving chromosomes during mitosis, and its formation begins in prophase. As the cell prepares for division, microtubular structures are organized so that chromosomes can later be aligned and separated properly. This event is part of the cell’s early preparation for accurate chromosome distribution. Without spindle formation, orderly movement of chromosomes would not be possible in later stages. The process therefore starts before alignment and separation occur. Hence, prophase is the stage during which the spindle apparatus begins to form.
117. Which event is most directly associated with metaphase of mitosis?
ⓐ. disappearance of nucleolus and breakdown of nuclear boundary
ⓑ. reappearance of the nuclear envelope around chromosomes
ⓒ. alignment of chromosomes at the equatorial plane
ⓓ. movement of chromatids toward opposite poles
Correct Answer: alignment of chromosomes at the equatorial plane
Explanation: Metaphase is the stage of mitosis in which chromosomes are arranged at the center of the cell. This central region is called the equatorial plane or metaphase plate. The alignment is important because it ensures that the sister chromatids are positioned for equal separation in the next stage. Metaphase is therefore known for order and arrangement rather than for condensation or final separation. The chromosomes become highly organized at this point. Thus, the most direct event associated with metaphase is alignment at the equatorial plane.
118. The equatorial plane in metaphase refers to:
ⓐ. the imaginary central plane where chromosomes align
ⓑ. the region where chromatids have already separated
ⓒ. the outer boundary of the spindle fibres
ⓓ. the place where cytokinesis begins
Correct Answer: the imaginary central plane where chromosomes align
Explanation: In metaphase, chromosomes do not remain scattered throughout the cell. Instead, they arrange themselves along an imaginary central line called the equatorial plane. This arrangement is important because it places all chromosomes in a balanced position before separation begins. The equatorial plane is therefore a spatial reference point in the middle of the dividing cell. It does not represent the area of cytokinesis or chromatid migration. Hence, it is best defined as the central plane where chromosomes align during metaphase.
119. Which statement best distinguishes prophase from metaphase?
ⓐ. In prophase chromatids separate, whereas in metaphase cytoplasm divides
ⓑ. In prophase nuclei reform, whereas in metaphase chromosomes condense
ⓒ. In prophase chromosomes move to poles, whereas in metaphase they become invisible
ⓓ. In prophase chromosomes condense, whereas in metaphase they align at the equator
Correct Answer: In prophase chromosomes condense, whereas in metaphase they align at the equator
Explanation: Prophase and metaphase are consecutive stages of mitosis, but they are recognized by different events. In prophase, the main feature is condensation of chromatin into visible chromosomes along with spindle preparation. In metaphase, the chromosomes are already condensed and now arrange themselves at the equatorial plane. This distinction helps in identifying the stage of a dividing cell under observation. Prophase emphasizes preparation and visibility, whereas metaphase emphasizes ordered alignment. Therefore, the best distinction is condensation in prophase and equatorial alignment in metaphase.
120. Chromosomes are most suitable for counting during metaphase because they are:
ⓐ. paired with homologous partners
ⓑ. highly condensed and clearly arranged
ⓒ. already split into daughter chromosomes
ⓓ. enclosed again within a reformed nucleus
Correct Answer: highly condensed and clearly arranged
Explanation: Metaphase is often considered the best stage for studying chromosome number because the chromosomes are at their maximum condensation and are distinctly visible. In addition, they are arranged neatly at the equatorial plane, which makes them easier to observe. This clarity allows cytologists to identify and count chromosomes more accurately. In other stages, chromosomes may be less organized or may already be moving apart. The ordered arrangement of metaphase provides the greatest visual advantage. Therefore, chromosomes are most suitable for counting during metaphase because they are highly condensed and clearly arranged.
