All Free Biology MCQs with Answers
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19844 questions · page 588 of 1985
5871. In the figure, mitosis is represented by which number?
- A. I
- B. II
- C. III
- D. IV
Explanation: In a typical representation of the cell cycle, mitosis is often represented by the number 4. This is because mitosis is the process of nuclear division that occurs during the M phase of the cell cycle, and in many diagrams or representations, the M phase is depicted as the fourth phase.
Correct answer: IV5872. Which number represents DNA synthesis in the figure above?
- A. I
- B. II
- C. III
- D. IV
Explanation: In a typical representation of the cell cycle, DNA synthesis (replication) occurs during the S phase, which is often represented by the number 2.
Correct answer: II5873. Which number represents the point in the cell cycle during which the chromosomes are replicated in the figure above?
- A. I
- B. II
- C. III
- D. IV
Explanation: In a typical representation of the cell cycle, DNA replication (chromosome duplication) occurs during the S phase, which is often represented by the number 2.
Correct answer: II5874. An enzyme that attaches a phosphate group to another molecule is called:
- A. Phosphatase
- B. Phosphorylase
- C. Kinase
- D. ATPase
Explanation: An enzyme that attaches a phosphate group to another molecule is called a kinase. Kinases are a large group of enzymes that play crucial roles in cell signaling, cell cycle regulation, metabolism, and many other cellular processes. They transfer phosphate groups from ATP to specific target molecules, often proteins, through a process known as phosphorylation.
Correct answer: Kinase5875. Which of the following are true concerning cells?
- A. They do not exhibit density-dependent inhibition when growing in culture
- B. When they stop dividing, they do so at random points in the cell cycle
- C. They are not subject to cell cycle controls
- D. None
Explanation: All statements provided are incorrect regarding cells.
Correct answer: None5876. Cells from an advanced malignant tumor most often have very abnormal chromosomes, and often an abnormal total number of chromosomes. Why might this occur?
- A. Cancer cells are no longer density dependent
- B. Cancer cells are no longer anchorage dependent
- C. Chromosomally abnormal cells can still go through cell cycle checkpoints
- D. Transformation introduces new chromosomes into cells
Explanation: Aneuploidy, characterized by an abnormal number of chromosomes, is a common feature of cancer cells. It can result from errors in chromosome segregation during cell division, leading to unequal distribution of chromosomes to daughter cells. Despite being chromosomally abnormal, cancer cells may still bypass cell cycle checkpoints due to dysregulation of cell cycle control mechanisms.
Correct answer: Chromosomally abnormal cells can still go through cell cycle checkpoints5877. Besides the ability of some cancer cells to over proliferate, what else could logically result in a tumor?
- A. Metastasis
- B. Changes in the order of cell cycle stages
- C. Lack of appropriate cell death
- D. Inability to form spindles
Explanation: In addition to over-proliferation, metastasis is indeed another logical consequence that could result from the development of a tumor. Metastasis is the process by which cancer cells spread from the primary site of the tumor to other parts of the body, where they establish secondary tumors.
Correct answer: Metastasis5878. Through a microscope, you can see a cell plate beginning to develop across the middle of a cell and nuclei re-forming on either side of the cell plate. This cell is most likely:
- A. An animal cell in the process of cytokinesis
- B. A plant cell in the process of cytokinesis
- C. An animal cell in the S phase of the cell cycle
- D. A bacterial cell dividing
Explanation: The description provided indicates cytokinesis, the process of dividing the cytoplasm of a cell, typically during telophase of mitosis or meiosis. The development of a cell plate across the middle of the cell and the re-formation of nuclei on either side of the cell plate suggest that the cell in question is a plant cell undergoing cytokinesis.
Correct answer: A plant cell in the process of cytokinesis5879. A particular cell has half as much DNA as some other cells in a mitotically active tissue. The cell in question is most likely in:
- A. G1
- B. G2
- C. Prophase
- D. Metaphase
Explanation: This is the first phase of cell cycle,where cell grows and carry out their normal functions.It is likely that the cell has not undergo replication yet therefore it is in G1 phase.Before entering S phase amount of DNA increases.
Correct answer: G15880. One difference between cancer cells and normal cells is that cancer cells:
- A. Are arrested at the S phase of the cell cycle
- B. Continue to divide even when they are tightly packed together
- C. Cannot function properly because they are affected by density dependent inhibition
- D. Are always in the M phase of the cell cycle
Explanation: Majority of cancer cells are always in the M phase of the cell cycle; they can be found in various phases depending on the specific characteristics of the tumor. However, certain aggressive or rapidly dividing cancer cells may exhibit a higher proportion of cells in the M phase due to their propensity for uncontrolled proliferation. This increased presence in the M phase contributes to the tumor's growth and aggressiveness, highlighting the dysregulation of cell cycle control mechanisms in cancer cells.
Correct answer: Are always in the M phase of the cell cycle