Question

The yeast genome and those of other eukaryotes show the presence of genes derived from both archaebacteria and eubacteria. The “informational genes” tend to have an archaeal character and the “metabolic genes” a eubacterial character. What are some possible explanations for this mixed eukaryotic genome?

Answer 1

The origin of eukaryotes is one of the hardest, forbidding and fundamental puzzle. Recent genomic analysis suggest that last eukaryotic common ancestor and modern eukaryotic cells have similar kind of complex feature. The last eukaryotic common ancestor was not the primitive organism and it was the resultant of extensive evolution.

• Evolutionary reconstructions showed that the complex ancestors was archaebacteria and the evolution may be due to gene loss.
• The cytoskeleton structure and ubiquitin system found in eukaryotes are also detected in archaea.
• The origin of major archaeal phyla was involved in acquisition of eubacteria genomes.

All these evidences together supports the theory of organizational complexity of eukaryotes comes from eubacteria and archaebacteria.

Eubacteria are the most simple cellular structure whereas eukaryotes are more complex in nature. Archaea is a mixture of these two. Some of archaea DNA replication is like that of eukaryotes. After evolution eubacteria and archaea diverged and after that by some complex means they exchange their genetic material and eubacteria incorporated a lot of endosymbiont DNA and eukaryotic genome formed. According to some theory eukaryotic cell was formed in combination between these two and nucleus is from archaea and cell membrane from mycobacteria and mitochondria from proteobacteria. All these theory are the some possible explanation for mixed eukaryotic genome.