OAT Biology - Problem Drill 06: Mitosis and Meiosis Question No. 1 of 10 1. During meiosis, cross-over between homologous chromosomes occurs at the end of. Question #01 (A) Anaphase II (B) Metaphase I (C) Metaphase II (D) Prophase I (E) Telophase II At the end of anaphase II, chromosomes are already separated with no chance for cross-over. At the end of metaphase I, chromosomes are aligned on the plate; cross-over has already occurred. C. Incorrect! At the end of metaphase II, sister chromosomes remain together; homologous chromosomes are separated in meiosis I and in different cells. D. Correct! Cross-over occurs at the end of prophase I when the homologous chromosomes are aligned and synapsed. At telophase II, cells are nearly completed with meiosis, with no cross-over. Cross-over is an important step in exchange of genetic material; the whole process is not fully understood yet, but it is important to know when it occurs. Cross-over may also occur during mitosis at prophase. The correct answer is (D).
Question No. 2 of 10 2. In humans, the somatic cells are diploid, having 46 chromosomes. Assume that cytokinesis occurs during late telophase during meiosis, how many chromosomes are present in one cell at anaphase II? Question #02 (A) 23 (B) 46 (C) 92 (D) 69 (E) None of the above After meiosis, there will be four cells, each containing 23 chromosomes. Therefore, after telophase II, the chromosome number will be 23. B. Correct! After Meiosis I, homologous chromosomes are separated, but sister chromatids are still attached to the same centromere. Therefore, they are counted as one chromosome. From telophase I to metaphase II, the chromosome number should be 23. After metaphase II, the sister chromosomes are separated; the chromosome number is back to 46 again. That is how many chromosomes are in the anaphase II. C. Incorrect! The cells never have 92 chromosomes, but they may have 92 chromatids. That is 1.5N; normally, this number of chromosomes does not exist in cells. There is one correct answer above. The key to solve this problem is to fully understand how chromosomes and chromatids behave during meiosis and to also understand the concept that when two chromatids are attached to the same centromere, it is counted as one chromosome. The correct answer is (B).
Question No. 3 of 10 3. This cell is undergoing mitosis. Which phase it is in? Question #03 (A) Prophase (B) Anaphase (C) Metaphase (D) Interphase (E) Telophase Prophase chromosomes are just condensed, not lined up yet. Anaphase chromosomes have separated sister chromosomes. C. Correct! Metaphase chromosomes are lined up at the metaphase plate; this is metaphase. Interphase is not part of mitosis. At telophase, the sister chromosomes are moved to two poles and are ready for cytokinesis. A characteristic of metaphase chromosomes is that they line up in the middle of the cell (metaphase plate). The correct answer is (C).
Question No. 4 of 10 4. Which of the following statements is NOT true of mitosis? Question #04 (A) A single cell gives rise to two identical daughter cells. (B) The centromeres divide at the onset of anaphase. (C) Homologous chromosomes synapse in prophase. (D) The daughter nuclei are genetically identical to the parent nucleus. (E) None of the above The statement is true. In mitosis, identical copies of the chromosomes are produced and placed in each of the daughter cells; cytokinesis divides the cytoplasm evenly and two identical daughter cells arise. The statement is true. The centromeres divide at anaphase so that each daughter cell can receive a chromatid. C. Correct! The statement is NOT true. Homologous chromosomes are independent in mitosis. Synapse or line-up of homologous chromosomes only occurs in prophase I of meiosis. The statement is true; two identical daughter nuclei are produced, and both are the same as the original cell. There is one correct answer above. One of the characteristics of meiosis is the synapse of homologous chromosomes, so that the genetic information can be exchanged between these chromosomes. The correct answer is (C).
Question No. 5 of 10 5. Cytokinesis in a plant cell is characterized by. Question #05 (A) The equal division of homologous chromosomes. (B) A pinching off of the cell membrane to divide the cell. (C) The synthesis of a cell plate in the cytoplasm. (D) The movement of the chromosomes from the metaphase plate. (E) The formation of two daughter cells. Mitosis in eukaryotic cells results in the equal division of all chromosomes. This is an explanation of cytokinesis for animal cells, lacking a cell wall. C. Correct! The spindle fibers are used to bring in vesicles that line up along the cell plate and produce a new cell wall. Movement from the metaphase plate occurs during the separation of chromatids. There are two daughter cells formed during cytokinesis, in both animal and plant tissue. Plant cells have cell walls, so when a plant cell undergoes mitosis, the cell wall needs to be synthesized between the two divided nuclei to form a new cell. The correct answer is (C).
Question No. 6 of 10 6. Which of the following statements about the difference between mitosis and meiosis is true? Question #06 (A) In mitosis, the daughter cells contain half the DNA of the parent cell. (B) In mitosis, the daughter cells contain twice the amount of DNA of the parent cell. (C) In both mitosis and meiosis, pairing and genetic recombination between homologous chromosomes takes place. (D) Only during meiosis does pairing and genetic recombination between homologous chromosomes take place. (E) Meiosis and mitosis contain two rounds of cell division. Mitosis in eukaryotic cells results in the equal division of all chromosomes. Mitosis in eukaryotic cells results in the equal division of all chromosomes. C. Incorrect! Only during meiosis does pairing and genetic recombination between homologous chromosomes take place. D. Correct! Only during meiosis does pairing and genetic recombination between homologous chromosomes take place. Mitosis only contains one round of cell division, whereas meiosis contains two. Somatic cells have 23 pairs of chromosomes (2N) and are diploid. Each pair is made up of one chromosome from the mother and one from the father; these are called homologous chromosomes. Meiosis is reduction division. It occurs in the germ cells and forms gametes that are haploid 1N. The correct answer is (D).
Question No. 7 of 10 7. Which of the following statements about interphase is true? Question #07 (A) The cell cycle consists of: interphase, mitosis and cell division. (B) The cell cycle consists of: interphase, cytokinesis and cell division. (C) The correct order of events during interphase is: G2, S, and G1. (D) The correct order of events during interphase is: S, G1 and G2. (E) During S phase, the DNA in the cell basically triples. A. Correct! The cell cycle consists of: interphase, mitosis and cell division. The cell cycle consists of: interphase, mitosis and cell division. C. Incorrect! The correct order of events during interphase is: G1, S, and G2. The correct order of events during interphase is: G1, S, and G2. During S phase, the DNA in the cell basically doubles. The cell cycle consists of: interphase, mitosis and cell division. The correct order of events during interphase is: G1, S, and G2. During S phase, the DNA in the cell basically doubles. The correct answer is (A).
Question No. 8 of 10 8. The cytoskeleton. Question #08 (A) Is made up of microtubules consisting mainly of tubulin and myosin. (B) Is made up of microtubules consisting mainly of myosin and activin. (C) Functions include: helping the cell keep its shape, enabling cell motion and being used in intracellular transport. (D) Functions include: helping the cell keep its shape and enabling cell motion, but it has no role in mitosis or meiosis. (E) Exists only in motile cells. The cell s skeleton is known as the cytoskeleton and is made up of microtubules consisting of tubulin and actin. The cell s skeleton is known as the cytoskeleton and is made up of microtubules consisting of tubulin and actin. C. Correct! The cytoskeleton functions: to help the cell keep its shape, to enable cell motion, and is used in intracellular transport. The cytoskeleton functions: to help the cell keep its shape, to enable cell motion, and is used in intracellular transport. The cytoskeleton exists in all cells. The cell s skeleton is known as the cytoskeleton and is made up of microtubules consisting of tubulin and actin. The cytoskeleton functions: to help the cell keep its shape, to enable cell motion, and is used in intracellular transport. The cytoskeleton exists in all cells. The correct answer is (C).
Question No. 9 of 10 9. What role do centrosomes play inside cells? Question #09 (A) The centrosome organizes the cell s microtubules and regulates cell cycle progression. (B) The centrosome disrupts the cell s microtubules and regulates cell division. (C) Centrosomes consist of a single centriole and are involved in assembling the mitotic spindle. (D) Centrosomes consist of a large group of centrioles and are involved in assembling the mitotic spindle. (E) During mitosis, the centrosomes both move to the same side of the cell. A. Correct! The centrosome organizes the cell s microtubules and regulates cell cycle progression. The centrosome organizes the cell s microtubules and regulates cell cycle progression. C. Incorrect! Centrosomes consist of two centrioles and are involved in assembling the mitotic spindle. Centrosomes consist of two centrioles and are involved in assembling the mitotic spindle. During mitosis, the centrosomes move away from one another to opposite ends of the cell. Centrosomes are made up of two centrioles, which interact with chromosomes during the mitosis. They play a major role in the migration of chromosomes to facilitate cell division. The correct answer is (A).
Question No. 10 of 10 10. Which of the following statements about the structure of chromosomes is true? Question #10 (A) A Satellite chromosome is a bulge at the centromere and has an enzyme necessary for the formation of the nucleolous after cell division. (B) A Satellite chromosome is a bulge at the telomere and has an enzyme necessary for the formation of the nuclear membrane after cell division. (C) A Telocentric, centromere is located at the end of the chromosome. (D) A Telocentric, centromere is located in the middle of the chromosome. (E) When the two arms of a chromosome are roughly equal in length, it s known as an acrocentric chromosome. A Satellite chromosome is a bulge at the telomere and has an enzyme necessary for the formation of the nucleolous after cell division. A Satellite chromosome is a bulge at the telomere and has an enzyme necessary for the formation of the nucleolous after cell division. C. Correct! A Telocentric, centromere is located at the end of the chromosome. A Telocentric, centromere is located at the end of the chromosome. When the two arms of a chromosome are roughly equal in length, it s known as a metacentric chromosome. There are three types of chromosomes: 1. Telocentric centromere is located on an end. 2. Acrocentric - centromere divides the two arms into a short and long arm name, p and q respectively. 3. Metacentric - centromere is located in the middle of the chromosome. The correct answer is (C).