Many receptor tyrosine kinase (RTK) pathways lead to the activation of Ras. To activate Ras, it is necessary to recruit a guanine nucleotide exchange factor to the plasma membrane, because Ras is a membrane associated protein. Guanine nucleotide exchange factors, such as SOS, stimulate the exchange of GDP for GTP. However, SOS cannot bind directly to most RTKs. The protein Grb2 has a domain that
can bind to phosphorylated tyrosines, and another domain that can bind to SOS. Therefore, Grb2 can bind to active RTKs and recruit SOS to the plasma membrane. Grb2 is an example of what kind of signaling molecule?
A. Scaffold
B. Adapter protein
C. Second messenger
D. Enzyme
B. Adapter protein
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If the att site of Escherichia coli was dissimilar to that of lambda phage due to a mutation, how would transduction be affected?
A. Phage DNA would be unable to integrate into host DNA. B. Lambda phage would be unable to package host DNA. C. Transduction would not be affected since mutation is only in the host cell. D. Specialized transduction would become generalized.
Which of the following statements about muscles is correct?
A. Smooth muscles contract more slowly than skeletal muscles. B. Actin and myosin are arranged irregularly in cardiac and smooth muscles. C. Skeletal muscles are striated, whereas cardiac muscles are not. D. Striated muscles use actin and myosin to generate force, whereas smooth muscles do not. E. Cardiac muscles are found in the heart and the walls of the arteries.
In your textbook, there is a discussion of the experiment by Wigglesworth that demonstrated that PTTH (prothoracicotropic hormone) triggers molting and the release of ecdysone
In 1984, Nagasawa et al. published a paper entitled: "Amino-terminal amino acid sequence of silkworm prothoracicotropic hormone: homology with insulin." The similar amino acid sequence between PTTH and insulin suggests that: A. a common ancestral peptide evolved into peptides with different functions in insects and invertebrates. B. if PTTH were given to vertebrates it would likely trigger glucose uptake by cells. C. insulin causes molting in vertebrates.
Shannon diversity (Hs)
A. goes up with increases in the number of species sampled and is higher when individuals are more equitably distributed among species. B. is higher when individuals are more equitably distributed among species. C. is independent of abundance. D. increases in areas undergoing secondary succession. E. is higher when individuals are more equitably distributed among species and is independent of abundance.