1.
The majority of a cell's life
Correct Answer
A. Interphase
Explanation
Interphase is the correct answer because it is the longest phase in the cell cycle where the cell grows, replicates its DNA, and prepares for cell division. It is a period of intense activity where the cell carries out its normal functions and prepares for the next stages of the cell cycle. This phase is crucial for the cell's growth and development before it enters the stages of mitosis (prophase, metaphase, anaphase, and telophase) where the cell divides into two daughter cells.
2.
DNA replication occurs
Correct Answer
A. Interphase
Explanation
During interphase, the DNA replication occurs. Interphase is the longest phase of the cell cycle, where the cell prepares for division by growing in size and replicating its DNA. This is necessary to ensure that each daughter cell receives a complete set of genetic information. DNA replication involves the unwinding and separation of the DNA strands, followed by the synthesis of new complementary strands. This process ensures genetic continuity and allows for the transmission of accurate genetic information to the next generation of cells.
3.
Chromosomes are very thin and not visible
Correct Answer
A. Interphase
Explanation
Interphase is the correct answer because it is the longest phase of the cell cycle where the cell prepares for division. During interphase, chromosomes are not visible because they are in a relaxed and uncondensed state. Instead, they exist as long, thin threads of chromatin. It is only during later stages of mitosis, such as prophase, metaphase, anaphase, and telophase, that the chromosomes condense and become visible under a microscope. Therefore, interphase is the phase where chromosomes are very thin and not visible.
4.
Nuclear membrane reforms
Correct Answer
E. Telophase
Explanation
During telophase, the nuclear membrane reforms around the two sets of chromosomes that have been pulled to opposite ends of the cell during anaphase. This marks the end of mitosis and the beginning of cytokinesis, where the cell divides into two separate daughter cells. The reforming of the nuclear membrane is crucial for the daughter cells to have their own separate nuclei and to maintain the integrity of their genetic material.
5.
Centromere of each chromosome splits
Correct Answer
anaphase
Explanation
During anaphase, the centromere of each chromosome splits, allowing the sister chromatids to separate and move towards opposite poles of the cell. This is a critical step in cell division as it ensures that each daughter cell receives the correct number of chromosomes. The splitting of the centromere is facilitated by the action of the spindle fibers, which exert force on the chromosomes. Once the centromere is divided, the sister chromatids are considered individual chromosomes and can migrate towards their respective poles.
6.
Chromosomes align and are pulled by spindle fibres
Correct Answer
metaphase
Explanation
During metaphase, the chromosomes align themselves along the equatorial plane of the cell and are attached to spindle fibers. These spindle fibers, which originate from the centrosomes at opposite poles of the cell, exert tension on the chromosomes, causing them to align properly. This alignment ensures that each daughter cell will receive the correct number of chromosomes during cell division. Therefore, the given answer accurately describes the events that occur during metaphase.
7.
Spindle fibres appear and centrioles migrate apart
Correct Answer
prophase
Explanation
During prophase, the spindle fibers appear and the centrioles migrate apart. Prophase is the first stage of mitosis, where the chromatin condenses into visible chromosomes. The spindle fibers, which are responsible for separating the chromosomes, start to form and extend from the centrioles. The centrioles, located near the nucleus, move towards opposite poles of the cell, preparing for the division process. Therefore, the appearance of spindle fibers and the migration of centrioles apart are characteristic events of the prophase stage.
8.
Nucleolus reappears
Correct Answer
telophase
Explanation
During telophase, the final stage of cell division, the nucleolus reappears. This is because in earlier stages of cell division, such as prophase and metaphase, the nucleolus becomes dispersed and is not visible. However, as the cell prepares to complete division, the nucleolus reforms within the newly formed daughter cells. This is an important step in the reestablishment of the nucleus and the resumption of normal cellular functions.
9.
Centrioles replicate
Correct Answer
interphase
Explanation
Interphase is the longest phase of the cell cycle, where the cell prepares for division by growing in size, replicating its DNA, and synthesizing proteins. During interphase, the centrioles, which are small structures involved in cell division, replicate as well. This replication ensures that each daughter cell will have the necessary centrioles to form the spindle fibers during mitosis or meiosis. Therefore, the given correct answer, "interphase," accurately describes the phase in which centrioles replicate.
10.
Each chromosome becomes attached to a spindle fibre
Correct Answer
prophase
Explanation
During prophase, the first stage of mitosis, the chromosomes condense and become visible. At this stage, the nuclear membrane also starts to break down. The spindle fibers, which are responsible for separating the chromosomes during cell division, begin to form and attach to the chromosomes. This attachment is crucial for the proper alignment and segregation of the chromosomes during later stages of mitosis. Therefore, the statement that each chromosome becomes attached to a spindle fiber accurately describes a key event that occurs during prophase.
11.
The chromatids which are now separate are called chromosomes
Correct Answer
anaphase
Explanation
During anaphase, the chromatids, which were previously duplicated during the S phase of the cell cycle, separate and move towards opposite poles of the cell. Once they separate, they are referred to as chromosomes. This process ensures that each daughter cell receives the correct number of chromosomes during cell division.
12.
Nucleolus is still visible
Correct Answer
interphase
Explanation
During interphase, the cell prepares for cell division by growing and replicating its DNA. The nucleolus, which is responsible for producing ribosomes, is still visible during this phase. This is because the nucleolus continues its function of synthesizing ribosomal RNA and assembling ribosomes, which are essential for protein synthesis. Therefore, the fact that the nucleolus is still visible supports the answer of interphase.
13.
Nuclear membrane is still present
Correct Answer
interphase
Explanation
During interphase, which is the longest phase of the cell cycle, the cell prepares for cell division by growing, replicating its DNA, and carrying out normal metabolic activities. The nuclear membrane is still present during interphase because it hasn't started breaking down yet, as it does during later stages of cell division. This allows the cell to continue its normal functions and prepares it for the next stages of the cell cycle, such as mitosis.
14.
Nucleolus disappears
Correct Answer
prophase
Explanation
During prophase, which is the first stage of mitosis, the nucleolus disappears. This is because the nucleolus is responsible for producing ribosomes, which are not needed during cell division. As the cell prepares to divide, the nucleolus breaks down and disappears, allowing the cell to focus on other important processes such as condensing its chromosomes and preparing for the separation of genetic material.
15.
Chromosomes are visible, condensed
Correct Answer
prophase
Explanation
During prophase, the first stage of mitosis, chromosomes become visible and condense. This is because the DNA inside the nucleus starts to coil tightly, forming distinct structures called chromosomes. These condensed chromosomes are easier to observe under a microscope. Prophase also involves the breakdown of the nuclear envelope and the formation of the spindle apparatus, which helps in the separation of chromosomes during cell division. Therefore, the given answer accurately describes the visible and condensed nature of chromosomes during prophase.
16.
Spindle fibres disappear
Correct Answer
telophase
Explanation
During telophase, the spindle fibers, which are responsible for separating the chromosomes, start to disappear. This is because their job is complete, and the chromosomes have successfully reached their respective poles. As the spindle fibers disappear, the nuclear envelope reforms around each set of chromosomes, and the cell prepares to enter the final stage of cell division, cytokinesis. Telophase marks the end of nuclear division and the beginning of the process of dividing the cytoplasm into two daughter cells.
17.
Twice as many chromosomes in the cell as there were in the parent cell
Correct Answer
anaphase
Explanation
During anaphase, the sister chromatids, which are replicated copies of each chromosome, separate and move towards opposite ends of the cell. This results in each new cell receiving a complete set of chromosomes, which is twice the number of chromosomes present in the parent cell. Therefore, the statement "twice as many chromosomes in the cell as there were in the parent cell" aligns with the process of anaphase.
18.
Chromosomes extend, become invisible again
Correct Answer
telophase
Explanation
During telophase, the chromosomes that were previously condensed and visible during metaphase and anaphase start to decondense. This decondensation causes the chromosomes to extend and become less visible under the microscope. Therefore, the given statement "chromosomes extend, become invisible again" accurately describes the events that occur during telophase.