Cell Cultures and Characteristics Questions and Answers

Q: The technique of organ culture may be divided on the basis of employing

Correct answer: both (1) and (2)Organ culture is done on a solid support - a plasma clot, agar, or a grid at the medium surface - or in liquid medium with the explant floating or rotated. The point of a solid support is to hold the tissue at the gas-liquid interface, so that it is nourished from below and oxygenated from above.

Q: For the selection of endospore-forming bacteria, a mixed culture can be heated at

Correct answer: 80°C for 10 minutesHeating a mixed culture to 80°C for 10 minutes kills all the vegetative cells while endospores survive, since they resist heat far better. Subculturing afterwards therefore yields only spore-formers - Bacillus and Clostridium. It is selection by physical means rather than chemical.

Q: Cell counting can be carried out by

Correct answer: all of the aboveAll three count cells. A counting chamber gives a direct microscopic total, live and dead alike; plate counting gives the viable count only, since each colony grew from a living cell; and a membrane filter concentrates organisms from a large dilute volume before they are counted or cultured, which is how water is tested.

Q: Which is the cell line derived from human embryonic lung?

Correct answer: MRC-5MRC-5 is a diploid fibroblast line derived from human embryonic lung tissue in 1966. Being a normal diploid line rather than a tumour line, it is used for producing viral vaccines. HeLa is from a cervical carcinoma and the L line from mouse.

Q: When a substance is added to a solid medium which inhibits the growth of unwanted bacteria but permits the growth of wanted bacteria, it is known as

Correct answer: selective mediumA selective medium is a solid medium containing an inhibitor - a dye, a bile salt, an antibiotic, or a high salt concentration - that stops unwanted organisms forming colonies while the wanted ones grow. The liquid counterpart is an enrichment medium.

Q: Which of the following is not a feature of plant cells?

Correct answer: Presence of centriolesHigher plant cells have no centrioles: their spindle is organised without them. What they do have, and animal cells do not, are plastids, a cell wall outside the membrane, a large central vacuole, and plasmodesmata connecting neighbouring cells through the wall.

Q: The concentration of agar to obtain semi solid media is

Correct answer: 0.5% or lessSemi-solid medium uses about 0.5% agar or less, giving a soft gel through which motile organisms can swim - which is how motility is tested, by whether growth spreads out from the stab line. A firm plate needs 1.5-2%.

Q: The material used in culture techniques is important because the surface of the vessel serves as a substrate for the cells to grow on.

Correct answer: TrueMost animal cells are anchorage dependent, so the surface itself is part of the culture system. Ordinary plastic is too hydrophobic, which is why culture vessels are surface treated to carry a charge, and why coatings of collagen, fibronectin or poly-lysine are used for cells that attach poorly.

Q: The ability of a single cell to divide and give rise to all the differentiated cells of the organism is called

Correct answer: TotipotencyTotipotency is the ability of a single cell to give rise to every cell type and so to a whole organism. Plant cells retain it, which is why a whole plant can be regenerated from callus. Pluripotent cells can form most but not all types, and multipotent only those of one lineage.

51.

The technique of organ culture may be divided on the basis of employing

A.solid medium
B.liquid medium
C.both (1) and (2)
D.semi-solid medium

Answer: C

Correct answer: both (1) and (2)

Organ culture is done on a solid support - a plasma clot, agar, or a grid at the medium surface - or in liquid medium with the explant floating or rotated. The point of a solid support is to hold the tissue at the gas-liquid interface, so that it is nourished from below and oxygenated from above.

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52.

An established cell line can be called where it has been subcultured at least

A.70 times at an interval of 3 days between subcultures
B.40 times at an interval of 3 days between subcultures
C.70 times at an interval of 1 day between subcultures
D.50 times at an interval of 3 days between subcultures

Answer: A

Correct answer: 70 times at an interval of 3 days between subcultures

The working definition of an established line is one subcultured about 70 times at three-day intervals - long past the fifty or so divisions at which a normal human cell reaches senescence. Surviving that many passages is the practical evidence that the line has become continuous.

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53.

For the selection of endospore-forming bacteria, a mixed culture can be heated at

A.80°C for 10 minutes
B.70°C for 10 minutes
C.60°C for 10 minutes
D.90°C for 10 minutes

Answer: A

Correct answer: 80°C for 10 minutes

Heating a mixed culture to 80°C for 10 minutes kills all the vegetative cells while endospores survive, since they resist heat far better. Subculturing afterwards therefore yields only spore-formers - Bacillus and Clostridium. It is selection by physical means rather than chemical.

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54.

Cell counting can be carried out by

A.direct microscopic count using a Petroff-Hausser counting chamber
B.plate counting
C.membrane filter count
D.all of the above

Answer: D

Correct answer: all of the above

All three count cells. A counting chamber gives a direct microscopic total, live and dead alike; plate counting gives the viable count only, since each colony grew from a living cell; and a membrane filter concentrates organisms from a large dilute volume before they are counted or cultured, which is how water is tested.

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55.

Which is the cell line derived from human embryonic lung?

A.HeLa
B.WISH
C.L
D.MRC-5

Answer: D

Correct answer: MRC-5

MRC-5 is a diploid fibroblast line derived from human embryonic lung tissue in 1966. Being a normal diploid line rather than a tumour line, it is used for producing viral vaccines. HeLa is from a cervical carcinoma and the L line from mouse.

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56.

When a substance is added to a solid medium which inhibits the growth of unwanted bacteria but permits the growth of wanted bacteria, it is known as

A.differential medium
B.enriched medium
C.enrichment medium
D.selective medium

Answer: D

Correct answer: selective medium

A selective medium is a solid medium containing an inhibitor - a dye, a bile salt, an antibiotic, or a high salt concentration - that stops unwanted organisms forming colonies while the wanted ones grow. The liquid counterpart is an enrichment medium.

Discuss in Forum

57.

Which of the following is not a feature of plant cells?

A.Consists of plastids
B.Cell wall outside the cell membrane
C.Presence of centrioles
D.Cell-cell communication through plasmodesmata

Answer: C

Correct answer: Presence of centrioles

Higher plant cells have no centrioles: their spindle is organised without them. What they do have, and animal cells do not, are plastids, a cell wall outside the membrane, a large central vacuole, and plasmodesmata connecting neighbouring cells through the wall.

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58.

The concentration of agar to obtain semi solid media is

A.1.5-20%
B.0.5% or less
C.>10%
D.>10%but<20%

Answer: B

Correct answer: 0.5% or less

Semi-solid medium uses about 0.5% agar or less, giving a soft gel through which motile organisms can swim - which is how motility is tested, by whether growth spreads out from the stab line. A firm plate needs 1.5-2%.

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59.

The material used in culture techniques is important because the surface of the vessel serves as a substrate for the cells to grow on.

A.True
B.False

Answer: A

Correct answer: True

Most animal cells are anchorage dependent, so the surface itself is part of the culture system. Ordinary plastic is too hydrophobic, which is why culture vessels are surface treated to carry a charge, and why coatings of collagen, fibronectin or poly-lysine are used for cells that attach poorly.

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60.

The ability of a single cell to divide and give rise to all the differentiated cells of the organism is called

A.Totipotency
B.Multipotent
C.Pluripotent
D.Unipotent

Answer: A

Correct answer: Totipotency

Totipotency is the ability of a single cell to give rise to every cell type and so to a whole organism. Plant cells retain it, which is why a whole plant can be regenerated from callus. Pluripotent cells can form most but not all types, and multipotent only those of one lineage.

Discuss in Forum

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