Factors (Score 2, Interesting)

I'm not surprised that people outside of science concentrates on "genes" when they speak of genetic material. The last estimate of the number of genes is about 20 000 (and that's being generous; for political reasons -- guess what they are -- some humans revise the estimate up). If we assume an average gene length of 2000 nucleotides, which codes for a protein over 650 amino acides long, then 2000 * 20000 accounts for only 4x10^7 nucleotides. Human DNA contains about 3x10^9 nucleotides. In other words, "genes" comprise only 1.3333% (up to about 5%, depending on what you define the average gene length to be) of the total DNA. The rest are (mis)named "junk DNA". (Be fair, we haven't figured out what the rest of it does... junk is as good a name as any other.)

That's the basic situation. Now, what governs which cells express what genes when has recently increased in complexity. Genes comprise regulatory sequences, where existing proteins and small RNA molecules can bind and impair or enhance gene expression (that is, reading the DNA into message, and then another reading where protein is made). Further, whether those regulatory proteins bind DNA coding stretches or not is governed by how the DNA/protein bundle unwinds itself. DNA doesn't just exist as a strand in a cell nucleus: it is, in a cell undergoing cell cycle, bound usually with proteins into a compressed bundle (3*10^9 nucleotides * 3x10^-10 m/nucleotide = .9 m) That's a long string to fit into a cell that's maybe .02 mm in diameter - and the nucleus is even smaller than that! At any rate, we are beginning to map even more of the factors that alter gene expression. The key is that DNA is bundled, and that adds a layer of regulation the cell which may inject minute differences between what otherwise would be identical cells.

I can't disagree with all the above posts on gestation environment and its affects on the embryo -- I only decry their vagueness. My point is that how would the womb affect the embryo? Without a mechanism, the musing is just that: an unsupported, random statement that gets us no where and allows no firm points for experimental remediation. I suggest one point where differences between Cc and its progenitor can be created: the existing egg into which the to-be-cloned DNA is inserted may have a diferent composition of proteins.

Another point I find disturbing is the mis-use of scientific ideas and concepts. I know there is much post-modernist wordplay, where academics in the humanities have tried to confuse everyone by playing with words, for example "gene." Likewise, "clone" became a loaded word since we associated the soul or personality with that concept. However, a "clone" is (scientifically) nothing more than two organisms containing the same exact DNA sequences. That's it; nothing more or less. Whatever else we push on the concept, that the clones must "act" the same or what have you, is just that: what we wish things to be.

There is nothing obvious about why the Cc does not behave the way its twin does. What a scientist means by that is quite different from what a non-scientist may think. The obvious argument is that, given similar initial states for two objects, how much of their patterns of change would remain the same? How soon after the start point would it become obvious that the endpoints of both objects be different? The answer lies in non-linear mathematics; an idea that falls from chaos math is that small initials differences lead to large systemic changes. Likewise, how much alike were the initial conditions for Cc and its twin? If we carry this argument through, it may be that an exact duplicate - where personalities and behavior patterns are the same -- is only a physical impossibility (where we cannot recreate the exact initial conditions) and not a theoretical one (if we could create the same conditions, then we would have duplicates). Hence, things are not so obvious after all. Keep in mind that I've only talked about genetic expression in a developing body: imagine how experiences would inject subtle changes into a developing mind!

Finally, my specialty is in systems neuroscience. I'm staggered by statements that trivialize the immense load of work that science has contributed to our understanding of how the brain works. We've only discussed single cells. Imagine networks of cells, specialized to transmit electrical impulses? In reality, whatever thinking and reacting animals perform must be based on these action potentials. Genetic expression is much too slow (the fastest gene expression based directly on neuronal activity occurs in minutes.) Action potentials carry on in the millisecond time domain. So, how do action potentials become "thoughts" and "memories"? I don't think we have a handle on that yet. Sure, we'll find papers where researchers have data supporting what mathematical algorithms a brain must be performing, but how does that generate a thought? What we can say now is that, the brain is created during part of the development of the embryo. The circuitry is created during this time, likely in the absence of neural activity. In this sense, there is hard-wiring. The retina must form a certain way; the hair cells responsible for hearing must be arranged in a certain way; these neurons must project to their relevant areas of the brain. Even at this point, there are synapses. A lot of them; much more than in a juvenile or an adult. What happens? The simplest story is that, it's easier to trim back connections than to create them. Why? I suppose another simple answer is that the system needs to choose relevant connections (imagine Pavlov's dogs.)

So, what else do neuroscientists mean by hard-wired? Remember the fight-or-flight impulse? In addition to the actual decision, the body coordinates its physiological responses to your decision. Adrenaline release, heart beat, sweat, stomach muscles stop churning, etc. These are hard-wired. How about other behaviors? Well, there's some evidence for that too: rub vinegar on your fingers and wave it under a baby's nose. Its nose will crinkle. Dip your finger in sugar water and give it to the baby, and it will suckle your finger. Tell me: When did the parents tell the kid, "hey, vinegar may be unpleasant" or "hey, sugar is OK"? Of course, these responses, over time, can change. Some of us develop a healthy appreciation for Italian dressing, and most of us control ourselves in a candy shop. In that one example, I've highlighted both nature and nurture. There is not only both, but there are behaviors that are expressly determined by one or the other. No neuroscientist means "cultural" norms when they speak of hard-wired behaviors; no one would deny that fires are painful and pulling your hand away from a hot surface is culture. There are many details that go into this, and I encourage everyone to read about them.