Tuesday, April 26, 2022

Cell cycle and cell division | Class 11 | Previous Years Questions and Answers (Web and PDF)

 CELL CYCLE AND CELL DIVISION

2020 MARCH


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.


Answer: Anaphase


2. Analyse the table given below and fill in the blanks.


(A)

(B)

Zygotene

....... (a) ........

....... (b) ........

Crossing over

....... (c) ........

Dissolution of synaptonemal complex

Diakinesis

....... (d) ........


Answer:

(a) Synapsis

(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


Answer: d. Pachytene


2. Given below is the diagrammatic representation of a particular stage of mitosis:

a.       Identify the stage.

b.       Write any two features of this stage. (2)

Answer:

(a) Anaphase

(b) Centromere 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.


Answer: Cleavage furrow.


2. Karyokinesis of mitosis is divided into 4 stages. Name the second and third stage. Write any two features of second stage.

Answer:

Second stage: Metaphase.

Third stage: Anaphase.

Features of second stage (Metaphase): All chromosomes at equator. Chromosomes at maximum condensation.


2018 JULY IMPROVEMENT


1. Observe the given stage of mitosis.

Identify the stage and write any two features of it.


Answer:

Telophase.

Features: Chromosomes cluster at opposite poles. Reforms nuclear envelope.


2018 MARCH


1.  First phase of meiosis I is typically longer and complex one. Name it. Mention the five subdivisions of this Phase. (3)


Answer:

Prophase I.

Leptotene, Zygotene, Pachytene, Diplotene, Diakinesis.


2.   Certain stages in cell cycle are given below. (3)

Karyokinesis, prophase, cytokinesis, metaphase, anaphase, telophase.

Choose the statements (from those given below) that match with these stages and prepare a table.

·     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.


Answer:

Anaphase / karyokinesis

Centromere splits and chromosomes move to opposite poles.

Telophase / Karyokinesis

Chromosomes cluster at opposite poles and nuclear envelope assembles around.

Prophase / Metaphase / karyokinesis

Chromosomes seems to be with two chromatids attached at centromere.

Metaphase / karyokinesis

Chromosomes arranged at spindle equator.

Anaphase / karyokinesis

Separation of daughter chromosomes

Cytokinesis

Division of cytoplasm


2017 JULY (IMPROVEMENT)


1. "Meiosis is highly significant in sexually reproducing organisms". Justify. (2)


Answer:

It ensures the conservation of specific chromosome number.

It creates genetic variation.


2. Give the scientific term of the following.

a) Interchange of genetic material between non-sister chromatids of homologous chromosomes. (1)


Answer: 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: Anaphase.

Two events of anaphase:

· Centromere of each chromosome divides longitudinally resulting in the formation of two daughter chromatids.

· As the spindle fibres contract, the chromatids move from the equator to the 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)


Answer:

a) Pachytene

b) 1) Meiosis conserves the specific chromosome number of each species across generations in sexually reproducing organisms.

    2)  It results in reduction of chromosome number by half.

    3)  It increases the genetic variability from one generation to the next.

    4)  Variations are very important for the process of evolution.


2015 SEPTEMBER (IMPROVEMENT)


1.  Observe the diagram related with cell cycle.


Identify and describe A, B and C in the diagram. (3) (Hint: Description of one point each from A, B and C).


Answer:

A= G1 phase              

B= S phase         

C= G2 phase


a.    G1 phase: First growth phase. Continuous growth of cell.

b.    S (Synthetic) phase: DNA replication takes place.

c.    G2 phase (Gap 2): Second growth phase. Cell growth continues.

OR

Write five sub-stages in prophase-I of meiosis. Point out in which sub-stage crossing over occurs.


Answer:

5 substages of Prophase I: Leptotene, Zygotene, Pachytene, Diplotene & Diakinesis.

Crossing over occurs in Pachytene (Pachynema) stage.


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)


Answer:

a) S phase.

b) x= Metaphase. Chromosomes come to lie at the equator.

 y= Anaphase. Chromatids move from the equator to the opposite poles. 


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