Which external factors influence a cell to divide?
What will be an ideal response?
ANSWER: A variety of external chemical and physical factors can influence cell division. Particularly
important for mammalian cells are growth factors, proteins released by one group of cells
that stimulate other cells to divide. Each cell type responds specifically to a certain growth
factor or combination of factors.
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Which of the following products of the light reactions of photosynthesis are later employed in the Calvin cycle?
a) ADP and RuBP b) free oxygen and water c) NADP+ and ATP d) NADPH and ATP e) electrons and H+
Pinworm is a nematode parasite that lives in the human rectum, and causes itching in the anal area. What best explains the itching symptom?
A. Any kind of parasite will naturally irritate the skin. B. The itching is because of the mismatch between humans and the parasite's natural host. C. The itching induces the person to scratch, helping to spread the parasite to another person. D. The itching is a side-effect when the immune system has successfully attacked the nematode.
A nerve impulse is initiated when
A. a reversal in the polarized state of the cell causes it to reach action potential. B. voltage-gated channels close. C. physical disruption of the cell membrane causes some of its contents, including ions, to leak out. D. the Schwann cells move into their new position.
Which of these is the best description of a dominant allele?
a. it is the allele that is expressed b. it is the most common allele c. it is the best allele d. both b and c