#Question id: 8781
#Unit 9. Diversity of Life Forms
The following question refers to this phylogenetic tree, depicting the origins of life and the three domains. Horizontal lines indicate instances of gene or genome transfer.
A possible phylogenetic tree for the three
domains of life.
Which of these processes can be included among those responsible for the horizontal components of the figure?
#Question id: 2860
#Unit 2. Cellular Organization
Lactose metabolism in E. coli is carried out by two enzymes, with possible involvement by a third. The genes for all three enzymes are clustered together and transcribed together from one promoter, yielding a polycistronic message. These three genes, linked in function, are therefore also linked in expression. They are turned off and on together.
|
Negative control |
keeps the lac operon repressed in the absence of lactose. |
|
positive control |
keeps the operon relatively inactive in the presence of glucose, even when lactose is present. |
|
when all the glucose is gone and lactose is present, a mechanism should exist. |
|
|
is mediated by a factor called catabolite activator protein (CAP), which, in conjunction with cyclic-AMP, stimulates transcription. |
#Question id: 2303
#Unit 2. Cellular Organization
During cell division spindle fibers attach themselves to the _______ located on the chromosomes.
#Question id: 5452
#Unit 8. Inheritance Biology
What are polygenes?
#Question id: 3783
#Unit 3. Fundamental Processes
What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?