Which among the following statements concerning platelets is INCORRECT. Platelets:
Answer: A
The incorrect statement is that platelets contain DNA.
They have no nucleus, being fragments budded off from megakaryocytes in the marrow. The rest is true: they are roughly disc-shaped, about 2 to 3 micrometres across against the red cell's 7, and synthesise very little protein.
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When looking at the cross section of the human tibia, where does one find the RED marrow in:
Answer: A
Red marrow is found in the medullary cavity of the tibia.
Red marrow makes blood cells; yellow marrow is fat. In a child almost all the marrow is red, and it is progressively replaced by yellow in the long bones with age, persisting in the flat bones and vertebrae.
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In which of the cerebral lobes is the speech centre located?
Answer: A
The speech centre lies in the frontal lobe.
Broca's area, in the lower frontal lobe of the dominant hemisphere - usually the left - controls the production of speech. Wernicke's area, in the temporal lobe, handles comprehension, and damage to the two gives quite different kinds of aphasia.
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What is the phase following metaphase in cell division known as?
Answer: B
The phase after metaphase is anaphase.
The order is prophase, metaphase, anaphase, telophase. In anaphase the centromeres divide and the spindle fibres pull the sister chromatids to opposite poles of the cell.
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How many contractile vacuoles are there in most species of Paramecium?
Answer: B
Most species of Paramecium have two contractile vacuoles, one at each end.
They collect the water that constantly enters the cell by osmosis, since the freshwater around it is more dilute than the cytoplasm, and expel it through a pore. Without them the cell would burst.
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