Shown below is an electron micrograph of part of a myofibril from a relaxed muscle fiber. Which of the labeled regions will not shorten when the muscle contracts?
A. Sarcomere
B. A band
C. I band
D. H band
Answer: B
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Beneficial relationships between two organisms, like the one observed between the cacao tree and endophyte fungi, are examples of
A. mimicry. B. parasitism. C. competition. D. commensalism. E. mutualism.
Which of the following is a possible cause of
colony collapse disorder (CCD)?
a. Israeli acute paralysis virus b. parasitic mites c. Nosema fungus d. neonicotinoid insecticides e. a combination of all of these is the possible cause of CCD
When G2 and M phase cells were fused together, the G2 nucleus became prematurely compacted when it was exposed to S phase cytoplasm in the fused cell. The G2 chromosomes could be seen to be visibly doubled. What conclusion was drawn from this result?
a) M phase cytoplasm contained diffusible factors that initiate DNA synthesis b) G2 nuclei cannot respond to diffusible factors present in M-phase cell cytoplasm c) the cytoplasm of the mitotic cell contained diffusible factors that could induct mitosis in a non-mitotic cell d) the cytoplasm of the G2 cell contained diffusible factors that could halt mitosis in a mitotic cell
Which of the following is true about ribosomes?
A) Ribosomes are organelles made of RNA and carbohydrates. B) Prokaryotic ribosomes have a lower overall mass and diameter than eukaryotic ribosomes. C) Ribosomes build amino acids by linking together nucleic acids. D) Prokaryotic ribosomes are also easily differentiated from eukaryotic ribosomes based on chemical composition. E) Antibiotics often take advantage of functional differences between prokaryotic and eukaryotic ribosomes.