Cell Cycle and Cell Division

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1 122 Cell Cycle and Cell Division 1. Meiosis I is reductional division. Meiosis II is equational division due to [1988] (a) pairing of homologous chromosomes (b) crossing over (c) separation of chromatids (d) disjunction of homologous chromosomes Meiosis II is an equational division which is meant for maintaining the haploid number, separating the two chromatids of a chromosome. 2. Segregation of mendelian factor (Aa) occurs during [1990] (a) Diplotene (b) Anaphase I (c) Zygotene/Pachytene (d) Anaphase II The paired homologous chromosomes separate in Anaphase I of meiosis I so that each gamete receives one chromosome of each homologous pair. 3. Mitotic anaphase differs from metaphase in possessing [1991] (a) same number of chromosomes and same number of chromatids (b) half number of chromosomes and half number of chromatids (c) half number of chromosomes and same number of chromatids (d) same number of chromosomes and half number of chromatids In mitotic anaphase, the sister chromatids separate from each other and begin to move towards the opposite poles. 4. In meiosis, the daughter cells differ from parent cell as well as amongst themselves due to [1991] (a) segregation, independent assortment and crossing over (b) segregation and crossing over (c) independent assortment and crossing over (d) segregation and independent assortment Due to segregation, independent assortment and crossing over at the time of meiosis, daughter cells exhibit variation. 5. Number of chromatids at metaphase is [1992] (a) two each in mitosis and meiosis (b) two in mitosis and one in meiosis (c) two in mitosis and four in meiosis (d) one in mitosis and two in meiosis In both mitotic and meiotic metaphase, the number of chromatids per chromosome is two. 6. Meiosis II performs [1993] (a) separation of sex chromosomes (b) synthesis of DNA and centromere (c) separation of homologous chromosomes (d) separation of chromatids Meiosis II is homotypic division specially for maintanence of the haploid number, separating the chromatids from each other in a chromosome. 7. Best stage to observe shape, size and number of chromosomes is [1994] (a) interphase (b) metaphase (c) prophase (d) telophase During metaphase, the centomeres of the chromosome lie on the equatorial plate according to their size and spatial arrangement. So it is the best time to count the number and study the morphology of chromosomes. 8. Meiosis is evolutionary significant because it result in [1994] (a) genetically similar daughters (b) four daughter cells (c) eggs and sperms (d) recombinations Meiosis provides a chance for new combinations of chromosomes mainly by the phenomenon of crossing over and

2 123 random distribution of homologous chromosomes between daughter cells. 9. The exchange of genetic material between chromatids of paired homologous chromosomes during first meiotic division is called [1996] (a) transformation (b) chiasmata (c) crossing over (d) synapsis The points of attachment between homologous chromosomes after their separation in diplotene are called chiasmata. The process of pairing of homologous chromosomes is called synapsis the phenomenon by which DNA isolated from one type of cell, when introduced into another type, is able to bestow some of the properties of the former to the latter is known as transformation. 10. In cell cycle, DNA replication takes place in [1996, 2000] (a) G1 phase (b) G2 phase (c) mitotic metaphase (d) S phase G 1 phase, also called Gap I phase is characterized by increase in cell size. In the S phase or synthetic phase DNA molecules replicate. G 2 is the second growth phase. Gap II where in there is intensive formation of RNAs and proteins. In the mitotic metaphase, the chromosomes are arranged at the equatorial plate. 11. Lampbrush chromosomes occur during [1996] (a) prophase of mitosis (b) diplotene of meiosis (c) metaphase of meiosis (d) interphase Lampbrush chromosomes are highly elongated bivalent chromosomes of diplotene stage, which are held together by chiasmata and have a large number of lateral loops for rapid transcription. 12. Colchicine is employed to diploidize a haploid cell as it [1996] (a) inhibits mitosis (b) inhibits formation of mitotic spindle (c) allows replication of DNA twice in one cell cycle (d) inhibits formation of centromere Colchicine is a mitotic poison which inhibits the appearance of spindle fibres. 13. Which one of the following structures will not be common to mitotic cells of higher plants? [1997] (a) cell plate (b) centriole (c) centromere (d) spindle fibres Plants cells do not have centrioles. Cell plate appears during cytokinesis in dividing cells. Centromere holds the sister chromatids in a chromosome. Spindle fibres appear during metaphase. 14. How many mitotic divisions are needed for a single cell to make 128 cells? [1997] (a) 7 (b) 14 (c) 28 (d) 64 In mitosis a single cell divides to form two daughter cells. 15. During cell division in apical meristem the nuclear membrane appears in [1997] (a) metaphase (b) anaphase (c) telophase (d) cytokinesis Metaphase in characterized by the appearance of spindle fibres. Anaphase involves movement of chromatids towards the poles. Cytokinesis marks the division of

3 124 the cytoplasm of the parent cell into daughter cells. 16. Microtubule is involved in the [1998] (a) cell division (b) muscle contraction (c) membrane architecture (d) dna recognition The spindle fibres involved in cell division is made of microtubules 17. A bacterium divides every 35 minutes. If a culture containing 105 cells per ml is grown for 175 minutes, what will be the cell concentration per ml after 175 minutes? [1998] (a) 5 105cells (b) cells (c) cells (d) cells 18. During cell division, the spindle fibres attach to the chromosome at a region called [2000] (a) chromocentre (b) kinetochore (c) centriole (d) chromomere Kinetochore is the proteinaceous covering of centriole, to which spindle fibers attach. 19. Best material for the study of mitosis in laboratory is [2002] (a) anther (b) root tip (c) leaf tip (d) ovary Anther cells are used to study mitosis. 20. If a diploid cell is treated with colchicine then it becomes [2002] (a) triploid (b) tetraploid (c) diploid (d) monoploid Colchicine inhibits spindle formation, due to which chromatids are unable to separate during anaphase which results in doubling of chromosomes. So, if a diploid cell is treated with colchicine, there is doubling of chromosomes and it becomes tetraploid,. Its an alkaloid obtained from Colchicum autumnale. 21. In the somatic cell cycle [2004] (a) In G1 phase DNA content is double the amount of DNA present in the original cell (b) DNA replication takes place in S-phase (c) a short interphase is followed by a long mitotic phase (d) G2 phase follows mitotic phase DNA replication is restricted to S- phase of interphase. G 2 phase is followed by the mitotic phase which is shorter than the inter phase. In G 2 phase DNA content is double than the amount present in the original cell. 22. If you are provided with root-tips of onion in your class and are asked to count the chromosomes, which of the following stages can you most conveniently look into? [2004] (a) Metaphase (b) Telophase (c) Anaphase (d) Prophase Chromosomes are most distinct in the metaphase stage. In the telophase stage they regain their coiled composition. In anaphase the chromatids separate and move towards opposite poles. In prophase stage the chromosomes appear thread like and individual chromatids cannot be seen. 23. Which one of the following precedes reformation of the nuclear envelope during M phase of the cell cycle [2004] (a) Decondensation from chromosomes, and reassembly of the nuclear lamina (b) Transcription from chromosomes, and reassembly of the nuclear lamina (c) Formation of the contractile ring, and formation of the phragmoplast (d) Formation of the contractile ring, and transcription from chromosomes At the beginning of M phase or mitotic phase the nuclear membrane and nucleolus disappear. The decondensation of chromosomes occur. But when nuclear envelop restart forming then nuclear

4 125 lamina assemble and chromosomes start condensing. 24. At what stage of the cell cycle are histone proteins synthesized in a eukaryotic cell? [2005] (a) During G-2 stage of prophase (b) During S-phase (c) During entire prophase (d) During telophase Histone proteins are synthesized during S- phase of cell cycle. S-phase or Synthetic phase. 25. During gamete formation, the enzyme recombinase participates during [2012] (a) Metaphase - I (b) Anaphase - II (c) Prophase - I (d) Prophase - II Recombinase enzyme catalyzes the exchange of short pieces of DNA between two long DNA strands particularly the exchange of homologous regions between the paired maternal and paternal chromosome in prophase - I. 26. Synapsis occurs between: [2009] (a) mrna and ribosomes (b) spindle fibres and centromere (c) two homologous chromosomes (d) a male and a female gamete Synapsis (also called syndesis) is the pairing of two homologous chromosomes that occurs during prophase I (zygotene stage) of meiosis. The two chromosome move together and pairing of corresponding points along their lengths as they lie side to side. The resulting structure is called a bivalent. 27. During mitosis ER and nucleolus begin to disappear at: [2010] (a) late prophase (b) early metaphase (c) late metaphase (d) early prophase During mitosis, endoplasmic reticulum and nucleus begins to disappear at early prophase. Also, nucleus and cell become spherical and DNA molecules condense to form shortened chromosome. 28. Which stages of cell division do the following figures A and B represent respectively? Fig. A Fig. B [2010] (a) Metaphase - Telophase (b) Telophase - Metaphase (c) Late Anaphase - Prophase (d) Prophase - Anaphase The figure represents late anaphase while figure B represent prophase stage of mitosis. 29. Select the correct option with respect to mitosis. [2011] (a) Chromatids separate but remain in the centre of the cell in anaphase. (b) Chromatids start moving towards opposite poles in telophase. (c) Golgi complex and endoplasmic reticulum are still visible at the end of prophase. (d) Chromosomes move to the spindle equator and get aligned along equatorial plate in metaphase In mitosis chromosomes move to the equator and get aligned along equatorial plate in metaphase. 30. At metaphase, chromosomes are attached to the spindle fibres by their: [2011M] (a) satellites (b) secondary constrictions (c) kinetochores (d) centromere Kinetochores are large protein complexes that bind the centromeres of chromosomes to the microtubules of mitotic spindle fibres during metaphase in the cell cycle. 31. During gamete formation, the enzyme recombinase participates during [2012] (a) Metaphase - I (b) Anaphase - II (c) Prophase - I (d) Prophase - II

5 126 Recombinase enzyme catalyzes the exchange of short pieces of DNA between two long DNA strands particularly the exchange of homologous regions between the paired maternal and paternal chromosome in prophase - I. 32. Given below is the representation of a certain event at a particular stage of a type of cell division. Which is this stage? [2012] (a) Prophase I during meiosis (b) Prophase II during meiosis (c) Prophase of Mitosis (d) Both prophase and metaphase of mitosis Diagram represents crossing over that takes place in pachytene stage of prophase - I during meiosis. 33. Identify the meiotic stage in which the homologous chromosomes separate while the sister chromatids remain associated at their centromeres? [2012M] (a) Metaphase I (b) Metaphase II (c) Anaphase I (d) Anaphase II Anaphase I begins when the two chromosomes of each bivalent (tetrad) separate and start moving toward opposite poles of the cell as a result of the action of the spindle. In anaphase I the sister chromatids remain attached at their centromeres and move together toward the poles. 34. A stage in cell division is shown in the figure. Select the answer which gives correct identification of the stage with its characteristics. [NEET 2013] (a) Late anaphase Chromosomes move away from equatorial plate, Golgi complex not present (b) Cytokinesis Cell plate formed, mitochondria distributed between two daughter cells (c) Telophase Endoplasmic reticulum and nucleolus not reformed yet (d) Telophase Nuclear envelop reforms, golgi complex reforms Telophase is the stage of reconstitution of nuclei. The chromosomes that have reached their respective poles decondense and lose their individuality and collect in a mass in the two poles. Nuclear envelope assemble around chromatin mass. Nucleolus, Golgi complex and ER reform. 35. The complex formed by a pair of synapsed homologous chromosomes is called [NEET 2013] (a) Kinetochore (b) Bivalent (c) Axoneme (d) Equatorial plate During zygotene, second stage of meiosis I, homologous chromosomes start pairing together forming a complex structure called synaptonemal complex. The complex formed by a pair of synapsed homologous chromosome is called a bivalent or a tetrad. Crossing over occurs between non sister chromatids of bivalent in the next stage. 36. During the metaphase stage of mitosis spindle fibres attach to chromosomes at [NEET Kar. 2013] (a) Centromere (b) Kinetochore (c) Both centromere and kinetochore (d) Centromere, kinetochore and areas adjoining centromere Kinetochores are small disc-shaped structures at the surface of the centromeres which serve as the sites of attachment of spindle fibres to the chromosomes that are moved into position at the centre of the cell. Hence, the metaphase is characterised by all the chromosomes coming to lie at the equator. 37. During meiosis I, the chromosomes start pairing at [NEET Kar. 2013] (a) Leptotene (b) Zygotene (c) Pachytene (d) Diplotene During zygotene, a substage of Prophase I of meiosis I, chromosomes start pairing together called synapsis. Such paired

6 127 chromosomes are called as homologous chromosomes. A complex structure i.e., synaptonemal complex is formed by a pair of synapsed homologous chromosomes called a bivalent or a tetrad. 38. Transpiration is least in [1988] (a) good soil moisture (b) high wind velocity (c) dry environment (d) high atmospheric humidity Transpiration is a process of loss of water in the form of vapours from the aerial parts of the plants. Transpiration is inversely proportional to the atmospheric humidity. The rate of transpiration would be higher when humidity is low.