In a cell-mediated immune response, how does a helper T cell activate cytotoxic T cells?
a. antibodies
b. cytokine signaling
c. receptor signaling
d. via cross-talk with macrophages
e. neural signaling
b
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The hypothesis that mitochondria and chloroplasts originated from the phagocytic activity of prokaryotes that was not
followed by digestion is called the ____.
a. theory of natural selection b. endosymbiotic hypothesis c. ribozymes-first hypothesis d. Oparin-Haldane hypothesis e. stromatolite hypothesis
Which of the following parts of the nervous system is closest to a muscle?
A) neuron B) interneuron C) motor neuron D) neuroglial cell
How were ancient peoples involved in biotechnology?
What will be an ideal response?
You are studying regulation of a prokaryotic operon. Experiments show that expression of the operon is increased when levels of biosynthetic product from that pathway are low. Based on this information, what is a likely mode of regulation?
A. The product binds a repressor, allowing it to bind the operator. B. The product binds a repressor, preventing it from binding the operator. C. The product binds an activator, helping RNA polymerase to bind the promoter. D. The product binds to the biosynthetic enzymes, blocking them directly.