Sciencism 2013/02/24

In this weeks episode of Sciencism Ross and Dan talk about the regenerative abilities of the newt and how this relates to the human genome, we talk about deep see vents, sharks with bio-luminescent fins, the origin of photosynthesis and the smallest ever exoplanet, we also talk about White Dwarfs in mini Science, and of course, last week in the past.

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Human Regrowth Efforts Take a Step Back

Humans as a species aren’t especially hardy unlike some species we’re not especially quick, we don’t have hard outer shells and most disappointingly unlike the red spotted newt we lack the ability to regenerate damaged tissues.

Researchers have long theorised that the genes for tissue regeneration evolved early in the lineage of multicellular organisms and that the sequences required may still be in the human genome lying dormant. This would mean if the right genetic sequences could be identified and activated at the right time humans too could regrow a limb or perhaps damaged heart muscle after an infarction.

Studying the genome of the Eastern newt has been challenging because its genome is ten times larger than a humans. Given the difficulty we have had with sequencing the human genome clearly sequencing the newts genome would be a big task.

Luckily there are other ways of studying the gene expression, and that is to study the RNA transcripts that are produced from the genomic DNA for gene control and protein expression. Braun et al who lead this latest research analysed more than 120,000 transcripts and about 15,000 coded for proteins. 826 were unique to the newt and were expressed at different levels in normal conditions compared to regenerated tissue.

Unfortunately the fact that these proteins are found in the newts only suggests that the ability to regenerate tissue evolved more recently and may not lie dormant in our genetic code which is a blow to research into this area of regenerative medicine. It is still possible that some forms of less impressive regeneration abilities are more ancestral and that we may be able to exploit those in the future.

How old is photosynthesis

Many will already be aware of a process called photosynthesis, this is the process by which plants use the energy from the sun to split water generating elemental oxygen as a by-product in a pathway called the Calvin cycle. This process is thought to be responsible for the oxygenation of the Earth 2.4 billion years ago, a vital pre-requisite of the complex life that would evolve later.

Preceding this process was a type of non-oxygen generating photosynthesis in which bacteria oxidise iron instead. Previous evidence found in South Africa suggest that the first bacteria to do so evolved around 3.4 billion years ago, however many geologists have been asking the question if any earlier evidence exists.

Andrew Czaja of the University of Cincinnati decided to look in the world’s oldest sedimentary rocks which are good at preserving evidence of life. The rocks are found in Greenland, in a previous episode we talked about how some of the oldest rocks on Earth are located there, 3.8 billion years old.  Using isotopic analysis he found that some of the isotopes of iron that were contained within the rocks were more common that if oxygen in the atmosphere has by chance oxidised the iron. The distribution of the isotopes was not uniform either varying from point to point.

These findings suggest that some form of photosynthetic bacteria had been responsible for the iron oxide because the microbes would oxidise different isotopes during different environmental conditions.

This places the evolution of photosynthesis a good 370millionyears older than previously thought, much closer to the time that life first arose and began to evolve on the planet.

1455 – Traditional date for the publication of the Gutenberg Bible, the first Western book printed with movable type.
1927 – German theoretical physicist Werner Heisenberg writes a letter to fellow physicist Wolfgang Pauli, in which he describes his uncertainty principle for the first time.
Feb 22
1632 – Galileo’s Dialogue Concerning the Two Chief World Systems is published. Compares Ptolemaic system with Copernican system
Feb 21
1842 – John Greenough is granted the first U.S. patent for the sewing machine.


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