Refer to the Gene Tree Shown

question 62

Essay

Refer to the gene tree shown. Ribosomal RNA genes are present in the nuclear genomes of eukaryotes.There are also rRNA genes in the genomes of mitochondria and chloroplasts.Therefore photosynthetic eukaryotes have three different sets of rRNA genes, which encode the structural RNA of three separate sets of ribosomes.Translation of each genome takes place on its own set of ribosomes.The gene tree shows the evolutionary relationships among rRNA gene sequences isolated from the nuclear genomes of humans, yeast, and corn; from an archaeal species (Halobacterium), a proteobacterium (E.coli), and a cyanobacterium (Chlorobium); and from the mitochondrial and chloroplast genomes of corn.
Based on the gene tree, how would you explain the closer relationship of the mitochondrial rRNA gene of corn to the rRNA gene of E.coli rather than to the nuclear rRNA genes of other eukaryotes? Can you explain the relationship of the rRNA gene from the chloroplast of corn to the rRNA gene of the cyanobacterium?

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