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UNIVERSAL EDUCATION ICSE GRADE X SUBJECT : BIOLOGY _____________________________________________________________________________ CHAPTER 2 - Cell cycle, Cell division and structure of chromosome. A. Name the following: 1. Acts as bearer of heredity unit. Chromosome. 2. The longest phase of cell cycle. Interphase. 3. Number of cells produced at the end of mitosis. Two. 4. Number of cells produced at the end of meiosis. Four. 5. The complex consisting of DNA strand and a core of histones. Nucleosome. 6. A region of plant body where cell division occurs very actively. Tips of the roots and stems. 7. Chromosome appears thread like. Prophase, telophase. 8. The type of cell division which occurs in the cell of the reproductive organ. Meiosis. 9. The phase in which the spindle fibers start contracting. Anaphase. 10. The phase in which the chromosome gets attached to spindle fiber. Metaphase. 11. The nuclear changes that occur during cell division. Karyokinesis. 12. Highly condensed coiled chromatin fiber. Chromosome. 13. Complex of DNA and histones. Nucleosome. 14. The point of attachment of chromatids. Centromere. 15. Repeating units that constitute the DNA strands. Nucleotides. B. State whether the following statements are true or false: 1. Mitosis is the type of cell division occurring in the cells of injured parts of the body. True. 2. Lysosome is a part of the cell in which chromosomes are present. False. Nucleus is a part of the cell in which chromosomes are present. 3. Centromere is the organelle of the cell that initiates cell division. True. 4. The resting phase of mitosis is called interphase. True. 5. Mitotic cell division cannot be mode of reproduction. False. Mitotic cell division can be a mode of reproduction as in case of asexual mode of reproduction. 6. Crossing over between chromatids can occur only between homologous chromosomes. True. 7. A nucleotide is composed of a sulphate, a sugar, and a nitrogenous base. False. A nucleotide is composed of a phosphate, a sugar, and nitrogenous base. 8. Genes are specific sequences of bases on chromosomes. True. 9. Histones constitute about 40% of total chromatin material. False, it constitutes about 60% of total chromatin material. 10. During the DNA replication the double helix opens from both the ends. False, During the DNA replication the double helix opens from one ends C. Fill in the blanks: 1. Mitosis occurs in somatic cells. 2. Mitosis produces two daughter cells whereas meiosis produces four daughter cells. 3. During meiosis the chromosome duplication is followed by two nuclear divisions. 4. Meiosis occurs only in reproductive cells. 5. Modern humans have 46 chromosomes. Their sperms and eggs will have 23 and 23 chromosomes respectively. 6. During the pairing of chromosomes in meiosis, the homologous chromosomes come to lie side by side. 7. The centrioles are surrounded by radiating rays called asters. 8. Chromatin fiber is made up of DNA and histones. 9. The chromatids are attached to each other at centrosome. 10. DNA replicates in the S phase of the cycle. 11. Rosalin franklin was the first to discover the structure of DNA. 12. The number of chromosomes in our skin cells is 46. 13. The spindle fibers are made up of microtubules. 14. Gametogenesis is the process by which gametes are produced. 15. The chromosomes which are exactly similar and bear same loci are called homologous chromosomes. 16. Cell division is the process by which cells multiply. 17. Meiosis is also known as reduction division. 18. All types of cells come from pre existing cells. 19. Cytokinesis is the division of cytoplasm. D. Choose the correct answer: 1. The number of chromosomes in a certain types of cell division is halved. This kind of cell division occurs in a. Only testis b. Only ovary c. Both ovary and testis d. All body cells Ans. c. Both ovary and testis. 2. In which of the following the two stages of meiosis have been given in correct sequences a. prophase, anaphase. b. metaphase, telophase. c. anaphase, metaphase. d. anaphase, telophase. Ans. d. anaphase, telophase. 3. The chromatin material is formed of a. DNA only b. DNA and histones c. Histones only d. Nucleotides Ans. b. DNA and histones 4. What is the correct sequence of stages in the cell cycle a. G1, S, G2, M b. G1, G2, S, M c. M, S, G1, G2 d. Cr, C, S, M Ans. a. G1, S, G2, M 5. DNA synthesis takes place during which stage. a. G1 phase. b. G2 phase c. S phase d. Prophase Ans. c. S phase 6. Chromosomes replication occurs in which phase? a. Interphase b. Prophase c. Telophase d. Metaphase Ans. a. Interphase 7. Chromosomes arrange at equatorial plate in which stage a. Prophase b. Metaphase c. Anaphase d. Telophase Ans. b. Metaphase 8. A phase which is reverse of prophase is a. Metaphase b. Interphase c. Telophase d. Anaphase Ans. c. Telophase 9. What is the function of centrosome? a. Initiation of cell division b. Inhibition of cell division c. Site for protein synthesis d. None of these Ans. a. Initiation of cell division 10. Cross- like structures formed during crossing over is called a. Chiasmata b. Golgi body c. Microbodies d. Centrioles Ans. a. Chiasmata 11. Chromosomes is mainly composed of which of these? a. DNA b. RNA c. ATP d. NADPH Ans. a. DNA 12. Duplicated chromosomes are joined at a point termed a. Centomere. b. Centrosomes c. Centriole d. Chromatid Ans. a. Centomere. E. Match the column: 1. Column I Karyokinesis Mitosis Interphase Cytokinesis Meiosis Synapsis Answers. Column I Karyokinesis Mitosis Interphase Cytokinesis Meiosis Synapsis Column II Resting phase Reduced division Pairing of homologous chromosomes Division of nucleus Somatic cell division Division of cytoplasm Column II Division of nucleus Somatic cell division Resting phase Division of cytoplasm Reduced division Pairing of homologous chromosomes 2. Column I Chromosomes are arranged in a horizontal plane at the equator Daughter chromosomes move to opposite poles Chromosomes becomes visible as fine long threads Chromosomes lose distinctiveness and gradually transformed into chromatin network Answers. Column I Chromosomes are arranged in a horizontal plane at the equator Daughter chromosomes move to opposite poles Chromosomes becomes visible as fine long threads Chromosomes lose distinctiveness and gradually transformed into chromatin network Column II Anaphase Prophase Telophase Metaphase Column II Metaphase Anaphase prophase Telophase F. Draw a neat labeled diagram to show the metaphase in an animal cell having four chromosomes. G. Diagram based questions: 1. Given below is a diagram of a double helical structure DNA. 1. Name the four nitrogenous bases that form DNA molecules. Adenine, guanine, thymine, cytosine. 2. Give the full form of DNA Deoxy-ribonucleic acid. 3. Name the unit of heredity Gene. 4. Mention two points of difference between Mitosis and Meiosis. Mitosis It occurs in somatic cells It results in the formation of two daughter cells, with same number of chromosomes as in parent cell Meiosis It occurs in reproductive cells It results in the formation of four daughter cells, with half the number of chromosomes as in parent cell 2. Given alongside is a diagram representing a stage during mitotic cell division in an animal cell: 1. Identify the above stage. Give a reason to support your answer. Late prophase. Reason: centrosomes splits into two, occupying each pole; nuclear membrane degenerates. 2. Name the parts labeled 1, 2, 3 and 4? 1: astral rays 2: Chomatid 3: Centromere 4: Spindle fibers. 3. What is the function of part 3? The division of centromere helps in the separation of two sister chromatids, which are drawn apart towards opposite poles. 4. Name the stage that comes just after the stage shown in the diagram. Draw a well labelled diagram of this stage. How can this stage be identified? Metaphase. The chromosomes arrange themselves in equatorial plane. 5. Name the cell organelle that is forms the aster . Centrosomes. 3. The diagram below represents a stage during cell division. Study the same and answer the questions that follows: 1. Name the parts labelled 1, 2 and 3 1: Asters 2: spindle fibers 3: daughter chromosomes 2. Identify the above stage and give a reason to support your answer. Late anaphase. As splitting of chromosomes takes place and daughter chromosomes proceeds towards the poles. 3. Mention where in the body this type of cell division occurs. Somatic cells/ body cells. 4. Name the stage prior to this stage. Metaphase. 4. Given below is a schematic diagram of a portion of DNA. Study the same and answer the questions that follows: 1. How many strands it is showing? Two. 2. How many nucleotides have been shown in each strand? Two. 3. Name the parts labelled 1, 2, 3, 4 and 5. 1- Phosphate 2- Pentose sugar 3- Nitrogenous base 4- Hydrogen bond 5- Nitrogenous bases 5. Given below is a diagram representing a stage during mitotic cell division. Study it carefully and answer the questions that follow. 1. Is it a plant cell or an animal cell? Give a reason to support your answer. An animal cell. As it shows the presence of centrioles. 2. Identify the stage shown. Late prophase. 3. Name the stage that follows the one shown here. How is that stage identified? Metaphase. The duplicated chromosome align themselves on the equatorial plane of the spindle. 4. How will you differentiate between mitosis and meiosis on the basis of the chromosome number in the daughter cell? Mitosis The daughter cells will have 46 chromosome Diploid in nature Meiosis The daughter cells will have 23 chromosome Haploid in nature 5. Draw a duplicate chromosome and label its parts.
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