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From a discussion on where are they? WHO are they?

Thought you might enjoy the content.

“WHO ARE THEY?

Genomes.

They get around on planet Earth.

You, dear friend, share fifty percent of your DNA with—yes—a banana.
While some folk were offended at the notion we might share genetic heritage with a chimpanzee—we do. And with his favorite yellow treat.

adenine (A), cytosine (C), guanine (G), and thymine (T) are nucleic acids that make up your DNA. And a banana’s.And the chimp’s.

It’s half the DNA spiral ladder..From Science Primer: Like DNA, RNA polymers are made up of chains of nucleotides *. These nucleotides have three parts: 1) a five carbon ribose sugar, 2) a phosphate molecule and 3) one of four nitrogenous bases: adenine, guanine, cytosine or uracil…don’t freak: I’m about to speak English.

Once cells ‘learned’ to reproduce themselves, life was off and running. And Earth’s genetic heritage is connected: dinosaur genes aren’t totally gone. We likely have some things in common—after all, they had hearts, livers, lungs, and other structures resembling us more than either of us resembles bananas.

The next question is—what other assemblage of chemicals would be self-reproducing, and carry information to organize a living body of some sort, change moderately over time, and derive materials from the environment?

How easily do these acids form in the environment? How easily do they associate? And how hardy are they?

I wouldn’t be that surprised to find, if we find evidence of Martian life, we find evidence of RNA-DNA chemistry…some of Mars may have landed on us, and they had a head start in cooling. I have more question regarding, say, Titan. Will we find a second viable system of doing genetic business?

Nitrogen, carbon, phosphorus, etc: the elements are the elements. The relative availablity varies from star to star, but the elements themselves are the elements, and certain ones combine easily and certain ones don’t combine without heating and pressure. Chemistry is chemistry. Some sugars, eg, wind left-handed and some right-. But basically, sugars are carbon, hydrogen, oxygen—water is hydrogen and oxygen…all pretty low on the periodic totempole.

Just sayin’. IANAC—I am not a chemist, nor a biochemist, but seems to me that given the same building blocks, similar heat and pressure, it may be a duplicatable result.”

52 comments to From a discussion on where are they? WHO are they?

  • This isn’t exactly a discussion of rotating left or right, but glucose, a 6-carbon sugar, is an interesting example of the importance of “handedness” (chirality). [As an aside, carbohydrates get their name because the chemical formula includes the equivalent of 1 water to each carbon. So, glucose has 6 carbons, 6 oxygens, and 12 hydrogens (I can’t figure out how to make the numbers become subscripts, so I won’t write the formula).] I hope my comment isn’t overly geeky and doesn’t derail the conversation!

    When a lot of glucose molecules join together in a long strand or chain (form a polymer), the manner in which they do so matters. For purposes of simplicity, I’m going to talk about only one connection: Carbon 1 connects to carbon 4. In one form, the -OH group attached to carbon 1 points down (this is the alpha form), and in the other form, the -OH group points out (this is the beta form).

    In a long polymer of the *alpha* form of glucose, the strand of molecules will naturally curve, so it coils up in a tidy package. This is what starch is made of.

    In a long polymer of the *beta* form of glucose, every other glucose molecule flips over, so the polymer is long and straight. Different strands can fit right next to each other. This is what cellulose is made of.

    We have an enzyme in our saliva, alpha-amylase, that can break apart the connections in a strand of starch, so that the individual sugar molecules are released. That’s why saltines will start to taste sweet if you chew them long enough.

    Herbivores like cows and sheep–and termites–have bacteria in their gut that *can* digest cellulose. We do not have an enzyme to break apart the connections in cellulose, and the microbes in our gut can’t digest cellulose, either.

    This website has a more detailed explanation and some animation showing the difference between alpha- and beta-glucose: http://www.pslc.ws/macrog/kidsmac/starlose.htm.

    As another aside, my degree is in biochemistry, but my training was more in proteins and organic chemistry than in genetics. That said, the linkages in double-stranded DNA are quite strong and stable, more so than those in RNA, which is usually single-stranded. DNA-RNA hybrids can be strong, too.

    The discussions on this post are fascinating! Thank you all!

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