The nucleolus is the site where
a. ribosomal RNA is transcribed and ribosomes are assembled.
b. DNA replication occurs.
c. proteins recently imported from the cytoplasm are deposited.
d. translation occurs.
Ans: a. ribosomal RNA is transcribed and ribosomes are assembled.
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A scientist is comparing mRNA translation in a mouse cell and a bacterial cell. He notes that translation occurs much more quickly in the bacterial cell. Why?
A. The bacterial cell contains more ribosomes than the mouse cell. B. The translation machinery in the mouse cell is very different from that in the bacterium. C. The bacterial genome contains more introns compared to that of the mouse. D. The lack of a definitive nucleus and nuclear membrane in the bacterium means that translation occurs faster. E. A mutation likely exists in the RNA polymerase of the bacterium.
You experimentally apply ?-bungarotoxin to a muscle and find that it does not contract when you electrically stimulate the motor neuron leading to it. You know that this toxin blocks acetylcholine receptors. Therefore, you suspect that the stimulation of contraction is failing at which of the following points?
A. A contraction fails to occur because acetylcholine is not released from the motor neuron. B. A contraction fails to occur because an action potential is not generated in the muscle cell. C. A contraction fails to occur because this toxin directly prevents calcium ion release from intracellular stores. D. A contraction fails to occur because neurotransmitter release by the motor neuron is blocked at the neuromuscular junction. E. A contraction fails to occur because this toxin prevents cross-bridge formation and thereby directly prevents contraction.
Proteoglycans are _____
A. both composed of collagen and provide resistance to compression. B. both composed of polysaccharides called glycosaminoglycans and provide resistance to compression. C. composed of polysaccharides called glycosaminoglycans. D. composed of collagen. E. resistant to compression.
What fraction of offspring of the cross AaBb × AaBb would be homozygous for both the dominant alleles, assuming that they are on different chromosomes?
A: 1/16 B: 1/32 C: 1/4 D: 1/8 E: 1/64