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Geologic Climate Research in Siberia

Aloha Mr. Martin (aka T-Mart)

So to continue with this idea that change has occurred in the past regarding increased levels of carbon dioxide...but not so quickly as right now....we would like to ask you and your scientists about photosynthetic organisms adapting to changes in levels of carbon dioxide using chloroplast DNA. This week we just learned that mitochondria and chloroplasts have their own DNA. We could understand why mitochondria had their own DNA, but why the heck would chloroplasts have THEIR own DNA?

So we ask, could the presence of chloroplast DNA allow photosynthetic organisms to adapt more quickly to changes in levels of carbon dioxide, especially because it is a circular DNA, simpler than more complex chromosomal DNA?

warmly, Mrs. P and her students wondering about mitochondria DNA and it's role in photosynthesis

Sat, 04/11/2009 - 16:39

Tim Martin

Mrs. P's class:
You stummped me! and you stumped all the the scientists here in camp... of course we are a bunch of geologists and earth scientists so we thought your question should be addressed to a biologist. Julie emailed your questions back to her University (U Mass)Biology department. From there it was sent to some specialists... Below is a respone from Professor Baskin:
Dear Julie and crew,
Tom Zoeller forwarded me your mail. I am a plant
biologist at UMass Amherst and I can comment on your question.
The first point: Why do chlorplasts have DNA? This is similar to the
mitochondrial DNA story. Chloroplasts like mitochondria are believed
to have originated as free living prokaryotic cells which were living
cooperatively with another kind of cell and eventually became
incorporated into that cell. The mitochondrial and chlroplast genomes
are thus leftovers. The genomes of those original procaryotic cells
were larger than the present-day genome remaining in the organelle,
and we can find many of those "original" genes today in the nuclear
genome. Evidently over evolutionary time, genes have relocated from
the prokaryotic genome in the organelle (mito or chloro) to the
nuclear genome. But the process never went to completion. I don't
know why and I don't think anyone does. But the result is that both
mitochondria have their own genes. But just a few genes. I believe
there are 16 genes in vertebrate mitochondria. Chloroplasts have 120
or so (I am not sure of the exact number). But this is way short of
being enough to make a cell. The organelles are not "little cells"
living independently inside the big cell. They are now pieces of
cellular machinery like any other organelle.
The second part of your question was about the pace of evolution and
possible organic response to raising CO2 levels. This touches on
several matters. Although the genomes in mitochondria and chlroplasts
have fewer genes this does not make them simpler or any more or less
subject to evolutionary selection. There are reasons why the rate of
evolution can differ between nulcear and organelle genomes. For one
thing, organelles are often although not always inherited from one
parent, not from both. For another, because the genomes are so small
the genes overlap and do other ticky things that can make them more
difficult to mutate and thus slow down their pace of change.
Lastly, rising CO2 levels per se are unlikely to cause permanent
problems for plants. Some plants that evolved to cope with low CO2
will be less favored and others will gain. The problem is that CO2
absorbs heat. Its like leaving your car parked in the sun with the
windows rolled up. It gets hot and unpleasant inside. For the earth,
this translates into more storms and unstable weather. Extreme
conditions that are difficult for anything to adapt to.
I hope this helps,
Tobias Baskin
Keep asking tough questions... that is how science moves forward!
T-Mart.

Sun, 05/02/2010 - 23:45

Anonymous

this is very interesting to know the things that have some past history just like Chloroplast DNA. the people who are in touch with such work they can start training as ccie lab are available for technical persons.