#Question id: 4096
#Unit 3. Fundamental Processes
The lambda repressor binds as a dimer to critical sites on the bacteriophage lambda genome to keep the lytic genes turned off, which allows the bacteriophage lambda genome to be maintained as a silent resident in the bacterial genome. Each molecule of the repressor consists of an N-terminal DNA-binding domain and a C-terminal dimerization domain. Upon induction (for example, by irradiation with ultraviolet light), the genes for lytic growth are expressed, bacteriophage lambda progeny are produced, and the bacterial cell lyses to release the viral progeny. Induction is initiated by cleavage of the lambda repressor at a site between the DNA-binding domain and the dimerization domain. In the absence of bound repressor, RNA polymerase initiates transcription of the lytic genes, triggering lytic growth.
A. Binding as monomers will be sufficiently weak that they do not compete with the binding of RNA polymerase. As a result, the genes for lytic growth will be turned on.
B. Binding as monomers will be sufficiently strong that they will compete with the binding of RNA polymerase. As a result, the genes for lysogenic growth will be turned on
C. The affinity of the dimeric lambda repressor for its binding site is the sum of all the interactions made by each DNA-binding domain. An individual DNA-binding domain will make just half the contacts and provide just half the binding energy as the dimer.
D. The affinity of the dimeric lambda repressor for its binding site is the sum of all the interactions made by each DNA-binding domain. An individual DNA-binding domain will make just double the contacts and provide just double the binding energy as the dimer.
Given that the number (concentration) of DNA-binding domains is unchanged by cleavage of the repressor, which of above outcomes will be possible?
#Question id: 2894
#Unit 2. Cellular Organization
Which of the following statements is INCORRECT regarding the assembly of DNA into higher-order chromatin structure?
I. Histone H1 is not part of the histone octamer, but binds to linker DNA and is responsible for higher-order chromatin structure.
II. The 30 nm fibers of a chromosome are attached to a/an RNA-protein scaffold that holds the fibers in large loops.
III. It is not possible for linear DNA to be supercoiled. Only circular DNA, which has no ends, can have regions of supercoiling.
IV. Core histones lacking their amino-terminal tails are capable of forming 30-nm fibers as they help to stabilize the 30-nm fiber in internucleosomal interactions.
#Question id: 1540
#Unit 4. Cell Communication and Cell Signaling
Peptidoglycans recognize by
#Question id: 14922
#Unit 8. Inheritance Biology
#Question id: 2192
#Unit 2. Cellular Organization
Site-directed cross-linking is a technique that gives insight into what property of integral membrane proteins?