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 Multiple Choice QuestionsMultiple Choice Questions

1.

Microtubules are the constituent of

  • spindle fibres, centrioles and cilia

  • centrioles, spindle fibres and chromatin

  • centrosome, nucleosomes and centrioles

  • cilia, flagella and peroxisomes


A.

spindle fibres, centrioles and cilia

Microtubules are structures present in cilia, flagella, centrioles and spindle fibres. They are also the part of fibres found in cytoskeleton. 

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2.

The cell -mediated immunity inside the human body is carried out by

  •  T- lymphocytes

  • B - lymphocytes

  • thrombocytes

  • erythrocytes


A.

 T- lymphocytes

T - lymphocyte receptors can recognise the only antigen that bound to cell membrane proteins these lymphocytes mediates CMI (cell-mediated immunity). B - lymphocytes are the major effector molecules of humoral immunity. Erythrocytes are red blood cells. Thrombocytes or platelets secrete factors that are involved in the vascular repair.

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3.

A stage in cell division is shown in the figure. Select the answer which gives correct identification of the stage with its characteristics

  • Telophase

    Nuclear envelope reforms, Golgi  complex reforms





  • Late anaphase

    Chromosomes move away from equatorial plate, Golgi complex not present

  • Cytokinesis

    Cell plate formed, Mitochondria distributed between  two daughter cells

  • Telophase

    Endoplasmic reticulum and nucleolus not reformed yet


A.

Telophase

Nuclear envelope reforms, Golgi  complex reforms





Telophase is the reserve of prophase. The chromosome that has reached their respective polar decondense and their individually. Late anaphase is characterised by centromeres split and chromatid moves to opposite poles. Cytokinesis is processed in which cell itself is divided two daughter cells.

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4.

In meiosis crossing over is initiated at

  • leptotene

  • zygotene

  • diplotene

  • pachytene


D.

pachytene

Crossing over takes place in pachytene stage. 

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5.

Which of the following is not a characteristic feature during mitosis in somatic cells?

  • Disappearance of nucleolus

  • Chromosome movement

  • Synapsis

  • Spindle fibres


C.

Synapsis

Synapsis is pairing of homologous chromosomes. It occurs during zygotene stage of meiosis

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6.

Meiosis takes place in

  • Meiocyte

  • Conidia

  • Gemmule

  • Megaspore


A.

Meiocyte

In diploid organisms, specialised cells called meiocytes(gamete mother cell) undergo meiosis. Conidia and gemmules are asexual reproductive structures found in penicillium and sponge respectively. Megaspores are female gametes in plants, which undergo sexual reproduction.

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7.

A cell at telophase stage is observed by a student in a plant brought from the field. He tells his teacher that this cell is not like other cells at telophase stage. there is no formation of cell plate and thus the cell is containing more number of chromosomes as compares to other dividing cells. This would result in

  • polyploidy

  • somaclonal variation

  • polyteny

  • aneuploidy


A.

polyploidy

Polyploid cells have a chromosome number that is more than double the haploid number.

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8.

Spindle fibres attach on to

  • kinetochore of the chromosome

  • centrosome of the chromosome

  • kinetosome of the chromosome

  • telomere of the centrosome


A.

kinetochore of the chromosome

Spindle fibres attach to kinetochores of chromosomes during cell division. They help the chromosomes to get separated to the two daughter cells, towards opposite poles. 

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9.

The complex formed by a pair of synapsed homologous chromosomes is called

  • equatorial plate

  • kinetochore

  • bivalent

  • axoneme


C.

bivalent

Homologous chromosomes pair up. This process is called synapsis. Each pair is called bivalent. Chromosomes line up around the equator of the spindle, attached by their centromeres to the spindle fibres, which are microtubules. The microtubules forming spindles can be of two types, i.e., kinetochore-microtubule and non-kinetochore microtubule.

Axoneme is the central core of a cilium of flagellum consisting of a central pair of filaments surrounded by nine other pairs. The equatorial plate is the plane located midway between the poles of a dividing cell during the metaphase stage of mitosis or meiosis. It is formed from the migration of the chromosome to the centre of the spindle.

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10.

Arrange the following events of meiosis in correct sequence:
(a) Crossing over
(b) Synapsis
(c) Terminalisation of chiasmata
(d) Disappearance of nucleolus

  • (b), (a,) (d), (c)

  • (b), (a) (c), (d)

  • (a), (b) (c), (d)

  • (b), (c) (d), (a)


B.

(b), (a) (c), (d)

The correct sequence of events of meiosis are:
Synapsis in zygotene  rightwards arrowCrossing over in pachytene  rightwards arrowTerminalisation of chiasmata in diplotene  rightwards arrow Disappearance of nucleolus in diakinesis.

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