All Free Biology MCQs with Answers

• A. An animal cell in telophase
• B. An animal cell undergoing cytokinesis
• C. A plant cell in metaphase
• D. A plant cell undergoing cytokinesis

Explanation: The formation of a cell plate across the middle of a cell and the re-formation of nuclei at opposite ends of the cell indicate that this is a plant cell undergoing cytokinesis after mitosis. In plant cells, cytokinesis involves the formation of a cell plate, which is made of vesicles containing cell wall material. The cell plate gradually expands outward from the center of the cell towards the cell walls, eventually dividing the cytoplasm into two daughter cells.

• A. The fibers of the mitotic spindle
• B. Anaphase
• C. Formation of the centrioles
• D. The S phase of the cell cycle

Explanation: Taxol, an anticancer drug, disrupts microtubule formation by binding to microtubules and stabilizing them, preventing their depolymerization. This stabilization of microtubules interferes with the normal dynamics of mitosis, particularly during anaphase. Taxol affects anaphase by interfering with the normal function of microtubules, thereby disrupting chromosome segregation and cell division.

• A. Kinetochores
• B. Golgi-derived vesicles
• C. Actin and myosin
• D. Centrioles and basal bodies

Explanation: Golgi-derived vesicles are primarily responsible for cytokinesis in plant cells. These vesicles contain cell wall materials such as cellulose, hemicellulose, and pectin, which are deposited at the cell plate during cytokinesis to form the new cell wall that separates the daughter cells.

• A. Telophase
• B. Prophase
• C. Metaphase
• D. Anaphase

Explanation: Chromosomes first become visible during the prophase stage of mitosis. In prophase, the chromatin condenses and coils tightly, forming distinct, visible structures called chromosomes. This condensation makes it easier for the cell to organize and separate the genetic material during cell division.

• A. From G1 of interphase through metaphase
• B. From metaphase through telophase
• C. From anaphase through telophase
• D. From G2 of interphase through metaphase

Explanation: During the phases of mitosis from G2 of interphase through metaphase, chromosomes are composed of two chromatids. This occurs after DNA replication during the S phase of interphase, where each chromosome is duplicated to form two sister chromatids held together by a centromere. These chromatids remain attached until they separate during anaphase of mitosis.

• A. Seedless plants
• B. Dinoflagellates
• C. Diatoms
• D. (B) and (C) only
• E. (A), (B) and (C)

Explanation: In seedless plants, which are a group of eukaryotic organisms, the nuclear envelope typically remains intact during mitosis. This is a characteristic feature of plants, including both seedless and seed-producing plants. Unlike in many animal cells where the nuclear envelope breaks down during mitosis, plant cells often undergo a process called closed mitosis, where the nuclear envelope remains intact throughout the process.

• A. G0
• B. G1
• C. S
• D. G2

Explanation: If the nucleus has 6 picograms of DNA, it suggests that it is in the G2 phase of the cell cycle. This is because during the S phase of interphase, DNA replication occurs, resulting in the doubling of DNA content. Therefore, in the G2 phase, just before mitosis begins, the DNA content is at its peak, having undergone replication.

• A. 8; 16
• B. 16; 8
• C. 16; 16
• D. 12; 16

Explanation: If a group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 8 picograms of DNA per nucleus, then at the end of the S phase, each nucleus would have 16 picograms of DNA. This is because during the S phase, DNA replication occurs, doubling the amount of DNA in each nucleus.At the end of the G2 phase, just before mitosis begins, the DNA content remains the same as at the end of the S phase. Therefore, each nucleus would still have 16 picograms of DNA. During the G2 phase, there is no additional DNA replication; instead, the cell prepares for mitosis.

• A. Meiosis
• B. Mitosis
• C. Replication
• D. Cytokinesis alone

Explanation: The somatic cells derived from a single-celled zygote divide primarily by mitosis. Mitosis is the process of cell division that produces two daughter cells with identical genetic material to the parent cell. It is responsible for growth, development, tissue repair, and asexual reproduction in multicellular organisms.

• A. Telophase
• B. Prophase
• C. Anaphase
• D. Metaphase

Explanation: The description provided indicates that the replicated chromosomes are aligned along the center (equator) of the cell. This alignment suggests that these cells are in the metaphase stage of mitosis. During metaphase, replicated chromosomes, consisting of two sister chromatids held together at the centromere, align along the metaphase plate (equatorial plate) of the cell.