Disaggregation of cells can be achieved by
Answer: D
Correct answer: all of the above
Disaggregation uses all three, usually together: physical disruption by mincing or sieving; enzymatic digestion with trypsin, collagenase or dispase to break down the matrix; and chelating agents such as EDTA to remove the calcium that the cell adhesion molecules need.
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Plate counts are often reported as
Answer: B
Correct answer: cfu/ml
A plate count is reported as colony-forming units per millilitre - per unit volume, since the count means nothing without knowing how much was plated. The term colony-forming unit is deliberately cautious: a colony may have grown from a clump rather than from one cell, so it counts units capable of forming a colony rather than individual organisms.
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Which of the following bacteria can grow in acidic pH?
Answer: B
Correct answer: Lactobacilli
Lactobacilli are acidophilic: they ferment sugars to lactic acid and tolerate the acidity they create, growing well below pH 5. That is what makes them the organisms of yoghurt, cheese and pickles - the acid preserves the food by excluding everything else. Vibrio cholerae is the opposite case, preferring alkaline conditions.
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According to Eagle, the growth of L-strain and Hela-strain cultures require to have mandatory presence of
Answer: D
Correct answer: 12 amino acids
Eagle showed that L-strain and HeLa cells require twelve amino acids in the medium - the nine essential for humans plus cysteine, tyrosine and glutamine, which cultured cells cannot make in sufficient quantity. His systematic omission experiments are the foundation of every defined medium since.
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Which of the following techniques is used for embryo culture?
Answer: D
Correct answer: All of these
Embryo culture uses all three approaches: organ culture on a plasma clot, the classical method; organ culture on agar, which gives a defined support; and whole embryo culture, in which the intact embryo is maintained. Which is used depends on the stage of the embryo and what is to be observed.
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The solidifying agent commonly used in preparation of media is/are
Answer: C
Correct answer: both (a) and (b)
Agar is the usual solidifying agent, and silica gel is used where agar cannot be - for autotrophs that would metabolise any organic material, since silica gel is entirely inorganic. Gelatin was used historically but melts at incubation temperature and is digested by many bacteria.
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The human fibroblast is a classical example of
Answer: A
Correct answer: stable primary cell lines
The human fibroblast is the classic finite (stable primary) line: it can be subcultured through some fifty population doublings and then stops dividing - the Hayflick limit - without ever becoming continuous. It keeps a normal diploid karyotype throughout, which is why such lines are used for vaccine production.
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Range of optimum glucose concentration present in the culture media is
Answer: A
Correct answer: 5.5 – 55 mmol/litre
Culture media hold glucose at about 5.5 to 55 mmol/litre - the lower end matching blood glucose, the higher end used where cells are to be grown to high density. Too much is not simply wasteful: excess glucose drives fermentation to lactate even in air, and the acid that results limits growth.
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Which of the following abnormality, resulted from the inheritance of an unbalanced complement of chromosomes can be diagnosed by karyotyping?
Answer: D
Correct answer: all of these
All three arise from an abnormal chromosome complement and are therefore visible in a karyotype: Down’s syndrome (trisomy 21), Turner’s syndrome (a single X), and Klinefelter’s syndrome (XXY). Karyotyping detects whole-chromosome faults; it cannot show a single-gene mutation.
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Which of the following chemotherapeutic agents may affect the growth of Campylobacter jejuni?
Answer: D
Correct answer: None of these
Vancomycin, polymyxin and trimethoprim are exactly what Campylobacter-selective media contain, because C. jejuni is resistant to all three while the competing gut flora are not. Their purpose is to suppress everything else, so none of them affects the organism being selected.
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