Last year the Craig Venter Institute announced that they had created an artificial bacterium. I thought I should follow up last months discussion of the Origin of Life with an overview of the claims, even though it is now considered 'old news' now.
Traditionally, genetically modified organisms (GMOs) are created by taking the DNA from an existing organism and identifying the gene responsible for a particular behaviour. In the most widely publicised cases, this has involved taking crop plants and adding genes from other species to add resistance to pesticides or to make the plant create an insect-repelling chemical.
In part 1, I discussed how early life may have arisen. In this part I will comment on one of the aspects of current terrestrial life - that of molecules symmetry or 'handedness'.
Molecular handedness, which chemists call Chirality, is a property of the 4 bonds which a carbon atom can form. If a particular carbon has 4 different groups of atoms attached to it, then there are two ways of attaching them such that one is a mirror image of the other. These are the two chiral forms, which are referred to as D- or L-isomers depending on the particular arrangement. In the 'skeleton' form of the amino acid Leucine, shown below, triangles mean the bond is pointing towards the viewer and the 'ladder' is a bond pointing away.
This week's science posting is in two parts. Part 1 covers a few theories about how life arose on Earth. Part 2 goes into a bit more detail on the molecules of life.
How Life came to Earth
There are two main theories on how life started on Earth: It came from Outer Space, and it started here on Earth. I will briefly describe the two approaches.
After last week's post about Yeast, I received a couple of questions asking for a bit of clarification. I thought it would be a good idea to post the questions and my response here.
This is the first in a short series of science-related posts where I will be explaining a bit of science behind some things which are of particular interest or relevence to me. I will be starting with fermentation since it is important in both baking and wine- and beer-making.
Q: When Halley's Comet reappeared in 1969, that winter a flu epidemic killed more than 60,000 people in Britain. In 2008 Comet Nostradamus (and others) passed by, and now we face a flu pandemic. Is this mere coincidence, or were the ancients right to fear comets as bad omens and bringers of pestilence? What other natural disasters have been attributed to comets?
An interesting question, and one which is wrong on almost every level. The question's author may be referring to the theory of panspermia, where micro-organisms or disease can be brought to Earth by comets. Unfortunately the question gets pretty much everything else wrong.
Halley's comet did not appear in 1969. It was around in 1910 and again in 1986. I can't find any record of a Comet Nostradamus. There is a bright comet every few years - they aren't that rare so claiming co-incidence doesn't really make sense. Also the Earth passes through comet dust several times per year. The major meteor showers are associated with dust and debris from comets. If comets were all full of germs and pestilence, then there would be major outbreaks several times per year.
At least the questioner didn't claim the world was going to end in 2012.