I have a question.
Feb. 21st, 2008 10:03 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
conuly
Okay. So, let's say you're looking at your average pea plant. And, following the rules of genetics as set out by Mendel, we know that if it's got one recessive gene for a trait, and one dominant gene for that same trait, the dominant one is the one we'll see.
Now, I'll interrupt a second and say that bio was never my subject. Chem was easy, and physics was a blast, but I only got through bio (the third time. Time one was a flop, and time two... well, I passed the tests, but I still wasn't able to really do the work) by memorizing a bunch of facts that didn't make much sense to me. (They made more sense once I took chem, and more again when I took physics. We teach high school science backwards.) So you'll correct me if I say anything devastatingly wrong.
Now, as I understand it, your chromosomes themselves just consist of a small number of nucleotides. So what makes a specific combination of nucleotides say "make this pea green" or "this one's gonna be a yellow pea" or even (in the case of extreme manipulation or random mutation) "purple all the way"?
For that matter, how does a pretty small difference in DNA make me a human, and outside we've got daisies? Or even a huge difference, every little detail different, how does it work to make things? How does it make sense?
I never understood that point. I just threw it back up on the tests, whatever I needed to know (the second and third years. The first year was a loss completely), and I've forgotten a lot of it, since I didn't really learn it properly the first (three) time(s) around.
Now, I'll interrupt a second and say that bio was never my subject. Chem was easy, and physics was a blast, but I only got through bio (the third time. Time one was a flop, and time two... well, I passed the tests, but I still wasn't able to really do the work) by memorizing a bunch of facts that didn't make much sense to me. (They made more sense once I took chem, and more again when I took physics. We teach high school science backwards.) So you'll correct me if I say anything devastatingly wrong.
Now, as I understand it, your chromosomes themselves just consist of a small number of nucleotides. So what makes a specific combination of nucleotides say "make this pea green" or "this one's gonna be a yellow pea" or even (in the case of extreme manipulation or random mutation) "purple all the way"?
For that matter, how does a pretty small difference in DNA make me a human, and outside we've got daisies? Or even a huge difference, every little detail different, how does it work to make things? How does it make sense?
I never understood that point. I just threw it back up on the tests, whatever I needed to know (the second and third years. The first year was a loss completely), and I've forgotten a lot of it, since I didn't really learn it properly the first (three) time(s) around.
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no subject
Date: 2008-02-22 05:27 am (UTC)The genetic 'alphabet' has a lot of redundancy in it. There are only 20 amino acids, but there are 64 different three-unit combinations. Two of them don't translate to anything and basically act as 'stop here' signals to let the RNA know where the gene ends and one of them acts as a 'start here' signal, but many of the rest code for the same amino acids as each other. This is important because it means that a lot of copying errors don't actually mess up the protein- for example, "AGU", "AGC" "UUC", "UUA", "UUG", and "UUU" all make the same amino acid, serine.
You're more likely to get a messed up protein by 'stutters' where a nucleic acid gets repeated too many times or two few, or frame-shifts (where it starts reading at the wrong point and basically makes gibberish (so rtofl ik eify ouin serted you rword brea kswrong.)