1. Observe the relationship between the first two terms and fill in the blank. (1)
Metaphase: Spindle fibres attach to kinetochores.
......................: Chromatids move to opposite poles.
2. Analyse the table given below and fill in the blanks.
Stage (A)
Event (B)
Zygotene
....... (a) ........
....... (b) ........
Crossing over
....... (c) ........
Dissolution of synaptonemal complex
Diakinesis
....... (d) ........
Answers:
1. Anaphase.
[Image of stages of mitosis anaphase and telophase]
2. (a) Synapsis (Pairing of homologous chromosomes).
(b) Pachytene.
(c) Diplotene.
(d) Terminalisation of chiasmata.
2019 July Improvement
1. Crossing over occurs in ............ substage of Prophase-I.
a. Leptotene b. Zygotene c. Diplotene d. Pachytene
a. Identify the stage.
b. Write any two features of this stage. (2)
Answers:
1. d. Pachytene.
2. a) Anaphase.
b) Features:
- Centromeres split and chromatids separate.
- Chromatids move to opposite poles.
2019 March
1. Fill in the blank.
Cytokinesis in animal cell takes place by the appearance of a ................... in the plasma membrane.
2. Karyokinesis of mitosis is divided into 4 stages. Name the second and third stage. Write any two features of second stage.
2. Second Stage: Metaphase.
Third Stage: Anaphase. Features of Metaphase:
- Spindle fibres attach to kinetochores of chromosomes.
- Chromosomes move to the spindle equator and align along the metaphase plate.
2018 July Improvement
1. Observe the given stage of mitosis.
Identify the stage and write any two features of it.
Answer:
Stage: Telophase.
Features:
- Chromosomes cluster at opposite spindle poles and their identity is lost as discrete elements.
- Nuclear envelope develops around the chromosome clusters.
- Nucleolus, golgi complex and ER reform.
2018 March
1. First phase of meiosis I is typically longer and complex one. Name it. Mention the five subdivisions of this Phase. (3)
2. Choose the statements (from those given below) that match with these stages and prepare a table: Karyokinesis, prophase, cytokinesis, metaphase, anaphase, telophase.
- Centromere split and chromosomes move to opposite poles.
- Chromosomes cluster at opposite poles and nuclear envelope assembles around.
- Chromosomes seems to be with two chromatids attached at centromere.
- Chromosomes arranged at spindle equator.
- Separation of daughter chromosomes.
- Division of cytoplasm.
Chromosomes seems to be with two chromatids attached at centromere.
Metaphase
Chromosomes arranged at spindle equator.
Anaphase
Centromere split and chromosomes move to opposite poles / Separation of daughter chromosomes.
Telophase
Chromosomes cluster at opposite poles and nuclear envelope assembles around.
Cytokinesis
Division of cytoplasm.
2017 July Improvement
1. "Meiosis is highly significant in sexually reproducing organisms". Justify. (2)
2. Give the scientific term of the following:
a) Interchange of genetic material between non-sister chromatids of homologous chromosomes. (1)
Answers:
1. Significance of Meiosis:
- It conserves the specific chromosome number of each species across generations.
- It increases genetic variability (important for evolution).
2. a) Crossing over.
2017 March
1. Given below is the metaphase of mitosis. Analyze the diagram and draw a sketch of anaphase. Write any two events of anaphase. (3)
Answer: (Students should draw Anaphase where chromatids move to opposite poles).
Events of Anaphase:
1. Centromeres split and chromatids separate.
2. Chromatids move to opposite poles.
2016 March
1. a) Identify the substages of meiosis in which crossing over is occurring.
i) Leptotene ii) Zygotene iii) Pachytene iv) Diplotene
b) Summarize the significance of meiosis in sexually reproducing organisms. (3)
Answers:
a) iii) Pachytene.
b) Significance:
- Conservation of chromosome number.
- Increases genetic variability.
- Essential for evolution.
2015 September (Improvement)
1. Observe the diagram related with cell cycle. Identify and describe A, B and C in the diagram. (3)
Answer: A = G1 phase: Interval between mitosis and initiation of DNA replication. Cell is metabolically active and grows continuously. B = S phase: Synthesis phase. DNA replication takes place. DNA content doubles (2C to 4C). C = G2 phase: Proteins are synthesized in preparation for mitosis while cell growth continues.
2015 March
1. Observe the diagrammatic view of a cell cycle and answer the questions:
a. Identify the phase in which DNA synthesis takes place. (1)
b. Mention any one event that takes place in the stages marked as 'x' and 'y'. (2)
Answers:
a) S phase.
b) x (Metaphase): Chromosomes align at the equator. y (Anaphase): Chromatids separate and move to opposite poles.
