mtDNA and Human Migration Patterns
The Endosymbiotic Hypothesis helps us understand the origins of eukaryotic cells and ultimately how the cells that compose complex organisms, such as humans, came to be. Not only has the hypothesis done this, but knowledge gained from it has allowed researchers to study the origins of man. The fact the mitochondria and chloroplasts both have a double membrane has lead scientists to believe that a primitive host ingested oxygen breathing bacteria and a photosynthetic bacteria that later developed into mitochondria and chloroplast respectively. Mitochondria and chloroplasts have many similarities to bacteria cells which is why it is believed that they originated from prokaryotic bacteria. A more astonishing feature of these organelles is that they have DNA separate from the DNA that can be found in the nucleus of the cell. The DNA chloroplasts and mitochondria contain various characteristics that have been used to distinguish the history of man. For example, mitochondrial DNA (mtDNA) is inherited to the child from the mother. Unlike other forms of DNA, changes in mtDNA occur at a much slower rate. These two characteristics have allowed genetic anthropologists to trace ancient migration patterns and to distinguish how humans came to populate the earth. Scientist are able to do this by analyzing a particular genetic marker on the mtDNA that after several generations is carried by a majority of the inhabitants in the region. As inhabitants of this region migrate to different areas of the world they carry this specific genetic marker with them. The specific genetic marker that each person has in their DNA can be used to indicate the migration pattern and location of that person’s ancestors.
The diagram above shows possible migration patterns (routes) that can be found through the analysis of mtDNA.
Spotted Salamander and Green Algae Endosymbiosis
Figure A: A late-stage salamander embryo inside its egg capsule; algae is present within it.
Figure B: Development of Algae on the Embryo (arrows point to developing sites).
In 2011 it was found that there was an endosymbiotic relationship between green algae and salamanders. In the recent publication, Intracellular invasion of green algae in a salamander host by Biologist Ryan Kerney, it was discovered that the spotted salamander lives with algae inside of its cells. Kearney and other biologist at Dalhousie University in Nova Scotia (Canada) were able to find large numbers of algae inside the embryos of salamanders. Before this discovery was made, it was long believed that a high concentration of algae floated outside the embryo in the eggs’ nutrient broth. After analyzing the embryos Kerney and his team were able to determine that the presence of algae was inside the embryo itself and not in the nutrient broth as originally perceived. Kerney was able to conclude the location of algae with the use of modern florescent microscopy. This form of microscopy targeted the highly florescent chlorophyll in algae and allowed Kerney to determine the presence of algae inside the embryo. The article goes on to state that in the early stages of development algae “suffuses” to the body of the embryo and becomes concentrated along the alimentary cannel and gut. This finding supports the ideas of Lambert Printz, who in 1927 noted the mutual benefits between the relationship of salamanders and algae. Further research done in the 1980s found that the algae oxygenate the embryos while the salamander eggs provide an environment rich in nitrogen. This nitrogen rich environment then fuels the growth of the algae. The presence of algae prevents deformities of the embryos which are common when algae are not present. Further experimentation during the time found that in the absence of green algae, salamander embryos do not develop as quickly.
This finding is analogous to the finding that anaerobic bacteria engulfed aerobic and photosynthetic bacteria to adapt to the changing oxygenated environment of the earth. As we can see from the article the salamander develops faster and avoids deformities when algae are present. In both cases endosymbiosis has allowed for both organisms to be better adapted to their environment and to strive within them. The Endosymbiotic hypothesis allowed for the development of eukaryotic cells which later went on to develop into complex organisms such as plants and animals. The article about the salamander is an example of the evolutionary potential of endosymbiosis in recent times.
Salamander embryos devlelop inside egg capsules that are covered with and infiltrated by a type of green algae.