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Q23 - Rhizobium Nodulation and Gene Structure in Lotus japonicus

Theoretical A Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license
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The effect of the nodule bacterium Rhizobium on the growth of the legume Lotus japonicus has often been studied, e.g. in relation to the enzyme/gene system of the interaction (Fig.). A, Rhizobium nodule and the relationship between the number of Rhizobium nodules and the nitrogen (N) content of soil. B, the enzyme CaMK with its mRNA and associated gene. The kinase domain (large dark grey) regulates other enzymes. The black band is the CaM domain, and the four narrow grey bands are EF- hand domains. Boxes in the gene are exons.

Figure 1. Figure 1.

Using the information and data, determine which of the statements are true or which are false.

A. Nodulation mainly occurs in nitrogen-poor soil
B. Rhizobium stimulates growth of Lotus by enlarging the surface of its root system; and consequently uptake of NO3- increases
C. Mutation 3G in Fig. B inhibits the transcription of CaMK
D. Each exon encodes a specific protein domain
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Question reproduced from IBO 2015, Theoretical Exam A, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)