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Cell as a Unit of Life

Description: This test will help the students to revise their topics thoroughly.
Number of Questions: 15
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Tags: cytokinesis Mitosis Golgi Bodies/Dictyosomes Endomembrane System of Cell Nuclear Organisation Cell Nucleus Cell Wall Outer Membrane System of Cell
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If a researcher examines primordial germ cells in a prepubertal human male under the microscope, in what stage of the cell cycle will he find them?

  1. Interphase

  2. Prophase

  3. Anaphase

  4. Telophase

  5. Metaphase


Correct Option: A
Explanation:

Interphase occurs just prior to cell division. Prepubertal male primordial germ cells are reactivated from interphase at puberty and enter rounds of mitoses followed by meiosis 1 and 2 to produce a unique haploid sperm.

Which among the following is a negative regulator of cell proliferation?

  1. p21

  2. p27

  3. p57

  4. p53

  5. p73


Correct Option: C
Explanation:

Cyclin-dependent kinase inhibitor 1C (p57) is a tight-binding inhibitor of several G1 cyclin/Cdk complexes and a negative regulator of cell proliferation.

In which of the following stages cell usually leaves cycling and stops dividing?

  1. G0 phase

  2. G1 phase

  3. S phase

  4. G2 phase

  5. M phase


Correct Option: A
Explanation:

A resting phase where the cell has left the cycle and has stopped dividing.

Which among the following statements regarding the cytokinesis in animal cells is false?

  1. It begins shortly after the onset of sister chromatid separation.

  2. A contractile ring, made of muscle myosin II and actin filaments, assembles parallelly at the cell cortex.

  3. The process of abscission physically cleaves this midbody into two.

  4. Abscission depends on septin filaments.

  5. The position at which the contractile ring assembles is dictated by the mitotic spindle.


Correct Option: B
Explanation:

A contractile ring, made of non-muscle myosin II and actin filaments, assembles equatorially (in the middle of the cell) at the cell cortex (adjacent to the cell membrane). Myosin II uses the free energy released when ATP is hydrolysed to move along these actin filaments, constricting the cell membrane to form a cleavage furrow.

The kinetochores are the protein structures found on chromatids. These are prominent in _____________.

  1. prophase

  2. prometaphase

  3. metaphase

  4. anaphase

  5. telophase


Correct Option: B
Explanation:

Prometaphase is the phase of mitosis following prophase and preceding metaphase, in eukaryotic somatic cells. In prometaphase, the nuclear membrane breaks apart into numerous membrane vesicles and the chromosomes inside form protein structures called kinetochores.

Which among the following chromosomes is not present in humans?

  1. Metacentric chromosome

  2. Subtelocentric chromosome

  3. Telocentric chromosome

  4. Submetacentric chromosome

  5. Acrocentric chromosome


Correct Option: C
Explanation:

Also known as the monarchial type of chromosomes, they have a centromere that is located towards the end of the chromosome. Thus, telocentric chromosomes have a 'rod' shaped appearance. In some cases, the telomeres extend from both the chromosome ends. The telocentric chromosome is not present in humans.

Which among the following statements does not characterise apoptosis?

  1. A cell initiates intracellular apoptotic signaling in response to a stress.

  2. The regulatory proteins initiate the apoptosis pathway.

  3. Targeting mitochondria functionality is one of the methods of apoptosis.

  4. Apoptosis produces cell fragments to be engulfed by phagocytic cells.

  5. Nitrous oxide has been implicated in initiating and inhibiting apoptosis.


Correct Option: E
Explanation:

Nitric oxide has been implicated in initiating and inhibiting apoptosis through its possible action as a signal molecule of subsequent pathways that activates apoptosis

Which among the following is not a function of the cell wall?

  1. Controlling turgor pressure

  2. Passage of substances

  3. Cell signaling

  4. Communication with other cells

  5. Carbohydrate storage


Correct Option: D
Explanation:

The protein molecules in the cell membrane receive signals from other cells or the outside environment and convert the signals to messages, that are passed to the organelles inside the cell.

In which of the following stages, the number of chromosomes per cell is 46 i.e. 2N and identical to the somatic cells of the human body?

  1. Growth 1 phase

  2. Anaphase II

  3. Prophase II

  4. Metaphase II

  5. Telophase II


Correct Option: A
Explanation:

Growth 1 phase is a very active period. In this period, the cell synthesizes vast range of proteins which includes the enzymes and structural proteins necessary for growth of the cell. In the G1 phase, the chromosome are made of single molecule of DNA, at this point in humans, the number of chromosomes per cell is 46 which is 2N and identical to the somatic cells.

The process of terminalisation occurs at _______________________.

  1. pachynema

  2. zygonema

  3. diplonema

  4. leptonema

  5. diakinesis


Correct Option: E
Explanation:

The chromosomes continue to pull apart, but non-sister chromatids are still loosely associated via the chiasma. The chiasma begins to move toward the ends of the tetrad as separation continues. This process is known as terminalisation. Also during diakinesis, the nuclear envelope breaks down and the spindle fibers begin to interact with the tetrad.

Which among the following is not a function of cytoplasm?

  1. It helps in the movement of the internal organelles.

  2. The enzymes in the cytosol break down large molecules, thereby helping the organelles to use them.

  3. Anaerobic glycolysis and protein synthesis takes place in the cytoplasm.

  4. Acts as a site for transcription.

  5. Cytoplasm provides support to the internal structures of the cell.


Correct Option: D
Explanation:

Nucleus is a site for transcription in which messenger RNA (mRNA) are produced for protein synthesis.

The cell organelle regarded as the post office of a cell is ______________.

  1. ribosome

  2. golgi bodies

  3. chromosomes

  4. cytoplasm

  5. lysosomes


Correct Option: B
Explanation:

It is the flattened membrane, which is mainly used to store the substances made by the cell. This membrane also helps in preserving and transporting materials within the cell. Hence, it is also called as the post office of a cell.

Who described the principle of apoptosis?

  1. Walther Flemming

  2. Karl Vogt

  3. Sydney Brenner

  4. Howard Robert Horvitz

  5. Carroll Milton


Correct Option: B
Explanation:

German scientist Karl Vogt was the first to describe the principle of apoptosis in 1842.

Cyclin-dependent kinases (CDKs) are the protein kinases which play a vital role in regulating the cell cycle. The CDK involved in the processes of neuronal maturation is _______________.

  1. CDK1

  2. CDK2

  3. CDK3

  4. CDK5

  5. CDK6


Correct Option: D
Explanation:

CDK5 is required for proper development of the brain. Cdk5 is involved in the processes of neuronal maturation and migration, phosphorylating the key intracellular adaptor of the reelin signaling chain.

The chromosomes formed due to the effects of certain chromosome-breaking process like irradiation is ______________.

  1. dicentric chromosomes

  2. polycentric chromosomes

  3. monocentric chromosomes

  4. acentric chromosomes

  5. holocentric chromosome


Correct Option: D
Explanation:

Acentric chromosomes are those that lack centromeres, i.e. the centromere is totally absent on the chromosome. These chromosomes are observed due to effects of chromosome-breaking process like irradiation.

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