The phylogenetic trees of the nifH and SSU rRNA genes are incongruent because
A) nitrogenase is an anaerobic enzyme.
B) nitrogenase evolves rapidly.
C) of horizontal gene transfer.
D) very few microbes have the nifH gene.

Question

Quizplus · Accepted Answer

Incongruence between phylogenies of different genes can be due to horizontal gene transfer, where genes are transferred between different organisms, leading to a discordance between the evolutionary history of the gene and the organism. This is a possible explanation for the incongruence between the phylogenetic trees of the nifH gene, which codes for a nitrogenase enzyme that is involved in nitrogen fixation and the SSU rRNA gene, which is involved in protein synthesis, since horizontal gene transfer is known to occur frequently among microbes.

The Phylogenetic Trees of the NifH and SSU RRNA Genes