From the relative positions of genes on the
chromosome illustration below, we expect
a. the highest frequency of crossing over between
genes A and D.
b. more crossing over between C and D than
between A and B.
c. more crossing over between A and B than
between B and C.
d. the lowest frequency of crossing over between B
and C.
e. none of these.
Answer: a
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Restriction endonucleases recognize specific sequences in the DNA
Indicate whether the statement is true or false
Which term is used to describe the overall 5?-to-3? direction of linked nucleotides in a DNA chain?
A) complementarity B) sequence C) polarity D) primacy
You are leading a team of researchers at a pharmaceutical company. Your goal is to design drugs that help fight cancer. Specifically, you want to focus on drugs that bind to and inactivate certain proteins, thereby halting cell cycle progression. One of your team members suggests targeting the retinoblastoma (Rb) protein and inhibiting this protein. Will this approach be successful? Why or why not?
A. This approach will not be successful. Rb is tumor-suppressor protein and functions to inhibit the action of a number of cell cycle regulatory proteins. A drug designed to inactivate the Rb protein would essentially create the same situation as in as a cell that lacks both copies of the Rb gene. Lack of Rb activity would release the inhibition of cell cycle regulatory proteins, thereby promoting cell cycle progression, rather than halting it. B. This approach will be successful. Rb is tumor-suppressor protein and functions to inhibit the action of a number of cell cycle regulatory proteins. A drug designed to inactivate the Rb protein would activate cell cycle inhibition. Lack of Rb activity would therefore inhibit the cell cycle regulatory proteins. C. This approach will not be successful. Rb is an oncogene and functions to activate a number of cell cycle regulatory proteins. A drug designed to inactivate the Rb protein would actually activate cell cycle progression. As a result, this drug would likely make this situation worse for patients whose cancer cells contain mutant Rb. D. This approach will be successful. Rb is an oncogene and functions to activate a number of cell cycle regulatory proteins. A drug designed to inactivate the Rb protein would halt the cell cycle in cells that contain an active Rb. As a result, cancer cells expressing a constitutively active Rb protein would be good targets for this type of therapeutic.
Secondary metabolites are often useful, and are obtained by
A) harvesting a culture during log phase. B) allowing a culture to enter stationary phase. C) growing a culture at sub-optimal temperature. D) adding chemicals that alter metabolic pathways. E) using continuous flow culturing.