After mutagenesis, the nitrogen-fixing bacterium Sinorhizobium meliloti could no longer colonize Medicago truncatula plants. This inability to colonize was due to the absence of recognition by the host plant
Which of the following genes is most likely the site of the mutation in these bacteria?
A) nitrogenase
B) flavonoid-synthesizing enzyme
C) Nod factors
D) leghemoglobin
E) peptidoglycans of the bacterial cell wall
V
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People who do not exhibit changes in blood pressure based on a circadian rhythm are more likely to have a heart
attack.
Indicate whether the statement is true or false.Why do researchers often include DNase in their antibiotic preparations to eliminate biofilms?
A. The antibiotics cannot readily penetrate the extracellular debris, which often includes DNA from lysed cells. B. Targeting the bacterial chromosome is the most effective way to kill biofilm bacteria. C. If the microbe's genome can be destroyed, the cell will die. D. The antibiotics target the cell wall and the DNase targets the genome, effectively destroying the biofilm.
In a tide pool, invertebrate species richness was 15. A researcher experimentally removed one species and over time the species count decreased to eight. The species removed was likely a(n)
A) mutualist. B) herbivore. C) detritivore. D) keystone species. E) C or D
There are cases, particularly in fruit flies, in which a normal body part grows in the wrong spot. For instance, legs on the head growing instead of antennae, or a second set of wings behind the normal pair. What can explain this?
A. These are due to misregulation of hormones from environmental contamination with pesticides. B. These naturally occur sometimes in animals that have metamorphic development, due to different organization of homeotic gene expression in larvae versus adults. C. These occur as a result of mutations in homeotic genes, which normally act to direct development along the anterior-posterior axis. D. These are due to the reappearance of stem cells, which are totipotent.