The enzyme beta-galactosidase acts on lactose to form galactose. In turn, the presence of galactose leads to expression of the enzymes responsible for the metabolism of galactose. In this case, lactose is serving as a carbon source and as a(n)
A. DNA-binding protein.
B. inducer.
C. repressor.
D. operon.
Answer: B
You might also like to view...
Paramecium is a single-cell eukaryotic organism that can reproduce by mitotic cell division. Prior to the M phase of the cell cycle, which of the following must occur?
A. The cell must replicate its chromosomes. B. The cell must first be fertilized. C. The nucleus must divide. D. Chromatids must be separated. E. The nuclear envelope must disintegrate.
A(n) ________ is a piece of DNA with all of the features necessary for chromosomal replication and which can carry large (up to 1000 kb) pieces of foreign DNA into a host organism.
What will be an ideal response?
Type S Streptococcus pneumoniae bacterium is lethal and will kill its host. If heat inactivated the S strain becomes nonlethal. Type R Streptococcous pneumoniae is a nonvirulent strain of bacteria. What would occur if one were to inject both the R strain and heat-killed S strains into a host organism such as the mouse?
A. The S strain would be transformed into the nonvirulent R strain and kill the host. B. The R strain would be transformed into the virulent S strain and kill the host. C. The S strain would be transformed into the nonvirulent R strain and not affect the host. D. The R strain would be transformed into the virulent S strain and not affect the host. E. Neither the S nor the R strain would change.
Which of the following is a nonrenewable resource?
a. copper and gold b. fresh water c. forests d. grasslands e. fish