1.
What feature in prokaryotes substitutes for the spindle action in eukaryotes?
Correct Answer
C. Elongation of plasma membrane
Explanation
In prokaryotes, the elongation of the plasma membrane serves as a substitute for the spindle action found in eukaryotes. This is because prokaryotes lack a nucleus and therefore do not undergo mitosis or meiosis like eukaryotes do. Instead, during cell division, the plasma membrane elongates and eventually pinches off, resulting in the separation of the two daughter cells. This process is known as binary fission and is the main method of reproduction in prokaryotes. Therefore, the elongation of the plasma membrane is the feature that replaces the spindle action in prokaryotes.
2.
How does a prokaryotic chromosome differ from a eukaryotic chromosome?
Correct Answer
B. A prokaryotic chromosome has a single loop DNA
Explanation
A prokaryotic chromosome differs from a eukaryotic chromosome because it has a single loop DNA. Unlike eukaryotic chromosomes that are linear and organized into multiple strands, prokaryotic chromosomes are circular and consist of a single loop of DNA. This structural difference is one of the key distinctions between prokaryotic and eukaryotic organisms.
3.
Which of the following is true for a diploid number of chromosomes?
Correct Answer
E. All of these are correct
Explanation
The statement "all of these are correct" is the correct answer because each of the statements listed is true. A diploid number of chromosomes refers to the 2n number, which is present in the parent cell and is also present in the two daughter cells following mitosis. The diploid number of chromosomes can vary depending on the particular organism. Additionally, the diploid number of chromosomes is found in somatic cells.
4.
What is the point of attachment for sister chromatids called?
Correct Answer
centromere
Explanation
The centromere is the point of attachment for sister chromatids, which are identical copies of a chromosome that are joined together. During cell division, the centromere plays a crucial role in ensuring that the sister chromatids are properly distributed to the daughter cells. It acts as a binding site for proteins that help in the separation of the chromatids, allowing each daughter cell to receive an equal and complete set of genetic material. Therefore, the centromere is essential for maintaining the integrity and stability of the genome.
5.
What is found at a spindle pole at the center of an aster?
Correct Answer
centriole
Explanation
A centriole is found at a spindle pole at the center of an aster. The aster is a radial array of microtubules that forms around the centrosome during cell division. The centriole is a cylindrical structure composed of microtubules and is located within the centrosome. It plays a crucial role in organizing the microtubules of the spindle apparatus, which are responsible for separating the chromosomes during cell division. Therefore, the presence of a centriole at the center of an aster is an accurate statement.
6.
What are coiled and condensed chromatin called?
Correct Answer
chromosome
Explanation
The term "coiled and condensed chromatin" refers to the tightly packed and organized form of DNA found in a chromosome. Chromosomes are structures within cells that contain genetic information in the form of DNA. During cell division, the chromatin condenses and coils into visible chromosomes, which can be observed under a microscope. This compact organization allows for efficient storage and transmission of genetic material during cell division. Therefore, the answer "chromosome" accurately describes the coiled and condensed form of chromatin.
7.
If a parent cell has 14 chromosomes before mitosis, how many chromosomes will each daughter cell have?
Correct Answer
B. 14 because the chromatids separate
Explanation
During mitosis, the parent cell undergoes division and separates into two daughter cells. Each daughter cell will receive an equal number of chromosomes as the parent cell had before mitosis. Since the parent cell had 14 chromosomes, each daughter cell will also have 14 chromosomes. This is because during mitosis, the chromatids, which are replicated copies of chromosomes, separate and are distributed equally to the daughter cells. Therefore, the correct answer is 14 because the chromatids separate.
8.
In which phase of mitosis are the chromosomes moving toward the poles?
Correct Answer
D. AnapHase
Explanation
In anaphase of mitosis, the chromosomes are moving towards the poles of the cell. During this phase, the sister chromatids separate and are pulled towards opposite ends of the cell by the spindle fibers. This movement ensures that each daughter cell will receive a complete set of chromosomes. Therefore, anaphase is the correct answer to the question.
9.
Which of these is true about interphase?
Correct Answer
E. Both a and b are correct
Explanation
The correct answer is "both a and b are correct". This is because interphase includes stages G1, S, and G2, which are the preparatory stages of the cell cycle before cell division occurs. Additionally, interphase is not the same as prophase, metaphase, anaphase, and telophase, which are the stages of mitosis. Therefore, both statements a and b are true.
10.
Which of these is true about cytokinesis?
Correct Answer
B. It requires the formation of a cell plate in plant cells.
Explanation
Cytokinesis is the process of dividing the cytoplasm of a cell into two daughter cells after mitosis. In plant cells, it requires the formation of a cell plate, which is a structure that forms in the middle of the cell and eventually develops into a new cell wall. This is different from animal cells, which undergo cytokinesis by forming a cleavage furrow. Therefore, the correct answer is that cytokinesis requires the formation of a cell plate in plant cells.
11.
At the metaphase plate during metaphase of mitosis, what is present?
Correct Answer
B. Unpaired duplicated chromosomes
Explanation
During metaphase of mitosis, the chromosomes align themselves along the metaphase plate. At this stage, the chromosomes are duplicated, meaning that each chromosome consists of two identical sister chromatids held together by a centromere. The duplicated chromosomes are unpaired because they are not yet separated into individual chromosomes. Therefore, the correct answer is "unpaired duplicated chromosomes."
12.
Which of this is true about a cell plate?
Correct Answer
E. Both a and b are correct
Explanation
The cell plate is a characteristic of plant cells because it forms during cell division and eventually becomes the cell wall. This process is known as cytokinesis and is necessary for the movement of chromosomes to ensure proper cell division. Therefore, both options a and b are correct.
13.
During which mitotic phases are duplicated chromosomes present?
Correct Answer
C. All but anapHase and telopHase
Explanation
Duplicated chromosomes are present during all phases of mitosis except for anaphase and telophase. In prophase, the chromosomes condense and become visible. In metaphase, the chromosomes line up along the metaphase plate. In telophase, the chromosomes start to decondense and form two separate nuclei. In anaphase, the duplicated chromosomes are pulled apart and move towards opposite ends of the cell. Therefore, the correct answer is all but anaphase and telophase.
14.
Which of these is paired incorrectly?
Correct Answer
E. TelopHase-a resting pHase between cell division cycles
Explanation
The given answer is correct because telophase is not a resting phase between cell division cycles. Telophase is the final stage of cell division where the nuclear envelope reforms around the separated daughter chromosomes, and the nucleolus reappears. It is followed by cytokinesis, which completes the cell division process. Therefore, telophase is not a resting phase but rather an active phase of cell division.
15.
When does cancer occur?
Correct Answer
A. When mutations have occurred
Explanation
The correct answer is "mutations have occurred." When cancer occurs, it is typically due to mutations that have taken place in the genes of cells. These mutations can lead to uncontrolled cell growth and division, which is a characteristic of cancer. Therefore, the presence of mutations is an important factor in the development of cancer.
16.
Which of the following is not characteristic of cancer cells?
Correct Answer
C. Cancer cells undergo apoptosis
Explanation
Cancer cells are known for their ability to evade programmed cell death, which is apoptosis. Unlike normal cells, cancer cells do not undergo apoptosis and instead continue to divide and proliferate uncontrollably. This ability to escape apoptosis is one of the characteristics that distinguishes cancer cells from normal cells.
17.
If a cell is cancerous, you might find abnormality in...
Correct Answer
D. All of these are correct
Explanation
If a cell is cancerous, it is likely to exhibit abnormalities in various aspects of its functioning. These abnormalities can be observed in receptor proteins, which are responsible for receiving signals from the external environment and transmitting them into the cell. Additionally, signaling proteins, which relay these signals within the cell, may also show abnormalities. Finally, cancer is often caused by mutations or alterations in genes, which can lead to uncontrolled cell growth and division. Therefore, it is reasonable to expect abnormalities in genes as well. Hence, all of these options are correct when considering the abnormalities that can be found in a cancerous cell.
18.
At the end of which stage does each chromosome consist of two identical DNA molecules?
Correct Answer
B. S stage
Explanation
During the S stage of the cell cycle, DNA replication occurs. This means that each chromosome, which is made up of a single DNA molecule, is replicated to form two identical DNA molecules. Therefore, at the end of the S stage, each chromosome consists of two identical DNA molecules.
19.
During which stage are daughter chromosomes distributed to two daughter nuclei?
Correct Answer
D. M
Explanation
During the M (mitosis) stage, daughter chromosomes are distributed to two daughter nuclei. This is the stage where cell division occurs and the replicated chromosomes are separated into two identical sets. The process involves the condensation and alignment of chromosomes at the center of the cell, followed by their separation and movement towards opposite poles. Once the chromosomes are successfully distributed, the cell undergoes cytokinesis, resulting in the formation of two daughter cells with identical genetic material.
20.
During which stage does the cell double its organelles and accumulate the materials needed for DNA synthesis?
Correct Answer
A. G1
Explanation
In the G1 phase of the cell cycle, the cell prepares for DNA synthesis by doubling its organelles and accumulating the necessary materials. This phase is characterized by cell growth and protein synthesis. Once the cell completes the G1 phase, it enters the S phase where DNA replication occurs. Therefore, the correct answer is G1.
21.
During which stage does the cell synthesize proteins needed for cell division?
Correct Answer
C. G2
Explanation
During the G2 phase of the cell cycle, the cell prepares for cell division by synthesizing proteins needed for the upcoming process. This phase follows the S phase, where DNA replication occurs, and precedes the M phase, where cell division actually takes place. G2 is a crucial checkpoint where the cell ensures that DNA replication has been completed accurately and that the necessary proteins and materials are available for successful division. Therefore, the statement suggests that the G2 phase is the correct phase for the cell to synthesize proteins required for cell division.
22.
Which is not true of the cell cycle?
Correct Answer
D. Apoptosis occurs frequently during the cell cycle
Explanation
Apoptosis is a programmed cell death process that occurs in response to specific signals or conditions, such as DNA damage or cell stress. It is not a frequent occurrence during the cell cycle, as the cell cycle is primarily focused on cell growth, DNA replication, and division. While apoptosis can be triggered during the cell cycle in certain circumstances, it is not a regular or frequent event in the normal progression of the cell cycle.
23.
In human beings, why is mitosis necessary?
Correct Answer
A. Growth and repair of tissues
Explanation
Mitosis is the process by which cells divide and replicate, resulting in the growth and repair of tissues in human beings. During mitosis, the chromosomes are duplicated and evenly distributed into two daughter cells, ensuring that the chromosome number is maintained in all body cells. Therefore, the correct answer is "Growth and repair of tissues."