okay, i think i remember from biology class that DNA is some kind of protein… right? and something about something called RNA too that does something. i know DNA is pretty much like a blueprint for everyone’s genetic information; but, as you can tell, i really don’t know much about it.
anyways, i was reading another supposed fact from this site that says
so, that got me thinking… what exactly are DNA made of? where are they? next to your liver or something? and what do they look like? what color are they… etc?
i’m sure i learned some of this from my biology book in 10th grade, but come on, that was the same book that said that the “jungle beats” in rock music makes the listener loe control of his actions.
A complete set of your DNA is in each and every cell in your body (except red blood cells). It is Dioxyribonucleic acid. Not a protein, but is made of building blocks in a similiar fashion. RNA (ribonucleic acid) is transcribed from DNA and ribosomes build proteins based on the order of the building blocks in the RNA.
DNA stands for deoxyribonucleic acid. Deoxyribose is a five carbon sugar that is kind of shaped like the big dipper with an oxygen at the top link . There is a phosphate on one of the carbons, and a base on another. There are four different bases that can be added to the deoxyribose to make the four different building blocks that make up DNA. The bases go by go by A, G, T, and C.
The phosphate of one molecule of DNA (the five carbon sugar + one base) connects to another molecule of DNA to form a chain. After two chains are formed, they connect to each other like two parts of a zipper. Base A on chain 1 will only form a strong bond with base T on chain 2, and base G will only bind strongly to base C. As the chains bind, they twist slightly, which creates the spiral shape of DNA.
So Deoxyribose is made up of carbons, oxygen, hydrogen and phosphorous. The four bases are made mostly of nitrogen and hydrogen bound in different structures. Three of the four also contain oxygen. Each cell of your body that has a nucleus (all except mature red blood cells) contains DNA. DNA is colorless.
I am not a molecular biologist, or even remotely close to one. But…
Omega Glory described the structure of DNA, but what does it do, you ask? Well, the sequence of base pairs are used to store information. That information is used to form messenger RNA which is a single chain of bases rather than a helix. This mRNA is released into the cell where large specialized molecules (ribosomes) essentially crawl along it and produce proteins based on the sequences of base triplets called codons. To simplify a lot, each codon matches one of 20 amino acids (http://www.agresearch.co.nz/scied/search/molecular/dnacodons.htm). When the ribosome that's translating the mRNA sees a series of three specific bases, it knows that it needs to grab a molecule of a specific amino acid (which are freely available floating around in the cell). It then appends that molecule to the protein that it's building and moves on to the next codon. It does this until it reaches a "stop" codon which says "this protein is done, cut it loose". The mechanism is at the same time both rather simple and amazingly complex.
The body has various clever ways of suppressing or initiating protein synthesis -- for example, the various ribosomes will only attach to various places on an RNA or DNA strand. So if you cover those binding sites, the protein won't get synthesized, and if you uncover them, it will be.
So, to really, really, really simplify, a lot of the work of the body is done by proteins. Proteins are constructed out of a sequence of amino acids. The DNA is the cookbook that says how to make each protein, with RNA being the intermediary.
Jungle beats in rock music makes the listener lose control of his actions, you say? We need more work on that, not this fancy dan carboxylic acid nonsense.
Sorry, can’t add anything sensible, but your post made me smile.
That 1.7 meter figure for a “single DNA molecule” is kind of bogus. Each base pair is about 3.4 Angstrom (10^-10 meter), so a whole haploid human genome of three billion base pairs would be about a meter long if it could be straightened out that way. But that consists of 23 separate chromosomes. The larger chromosomes would only be about a tenth of a meter. Still surprisingly large, considering that they fit into cells.
Each of the bases (Adenine, Guanine, Cytosine, Thymine) fits only one of the others. Unfortunately, I can never remember what the pairs are. So when a cell reproduces and the DNA splits down the middle, each base grabs on to its partner base.
Most cells split in a process called mitosis. This results in two cells with all the DNA of the original (all kinds of things can go wrong, and mutations can occur. But, I’ll leave that for another Doper to explain). Egg and sperm cells, however, are produced by meiosis. This results in cells with half the DNA of the original (again, things can go wrong and all kinds of mutations may occur). When a sperm cell bashes its way into an ova, the two DNA halves form a new whole and the cell begins to divide like crazy.
The pairs are adenine-thymine and guanine-cytosine. Each base can pair with only one other base. The rest of the structure of DNA has already been explained. Basically, DNA is two long strands of nucleotides that are held together by the attraction between the bases. Each nucleotide is made up of a base (A, T, G, or C), a sugar (deoxyribose), and a phosphate unit (PO[sub]4[/sub]). Each nucleotide is connected to the next by the phosphates. A diagram would explain this much better than I can here.
DNA is located in the nucleus of each cell. If you extract DNA from some cells (which is easy to do), you get a lump of white gelatinous stuff that seems kind of stringy.
RNA is chemically similar to DNA except that the sugar is ribose instead of deoxyribose (which has one less oxygen atom than ribose) and one of the bases, thymine, is replaced by uracil. RNA is not always double-stranded; DNA almost always is. The functional difference between them is that DNA is much more stable than RNA, which is relatively easy to break down.
The “other stuff” that makes up the chromosome is protein. Usually, the chromosomes are long strands that can’t be seen, but when a cell prepares to divide, the DNA wraps tightly around circular proteins called histones, and becomes visible. The “X” shape that the chromosomes are often drawn as, are made up of two identical strands of DNA called chromatids. When the cell splits in two, each new cell will get one half of the X.
RNA is confuses the equation because it has Uridine instead of Thymidine. Has there ever been any particular theory advanced for why RNA differs in this way?
A small hijack: I 've read in a book that there is too much information about a human body(eg, hair color, height, skin color, eye color etc.) and the DNA is too small to have all that info coded into its structure. Is that true? If it is true, then where does the “extra” information come from?
There are several reasons why DNA might have thymine instead of uracil. One is that uracil forms non-Watson-Crick base pairings much more easily than thymine. Uracil often pairs with bases other than adenine, while thymine pairs more selectively with adenine. Proper base pairing is more important in DNA than RNA (which is often single-stranded), while unusual base pairing is occasionally important in RNAs. Another reason is that having a base that is unique to DNA makes it more difficult for viral or bacterial proteins to attack DNA.
The reason why DNA uses deoxyribose instead of ribose is that ribose can easily form a cyclic intermediate (with the 2’-OH and the 3’ phosphate) that readily decomposes, resulting in cleavage of the polynucleotide. DNA does not have a 2’-OH, and cannot do this. Since DNA lacks a really favorable pathway for cleaving the polynucleotide, it can last much longer. DNAs may be required to last for the whole lifetime of the organism (and have been observed to last millions of years after its death), while RNAs are used briefly as messengers or catalysts, then chopped up and recycled.
Would that be a religious or ID book, I’m guessing? No, not true, not even close. DNA is huge. The complete set of genes in each of your cells is 3 billion base pairs.
DNA is not protein, it is the blueprint from which the body makes all proteins. RNA is part of the process of making proteins from the info contained in the DNA.
As others have said here it is in every single cell in your body, in the nucleus, it does not reside in any one spot within the body.
Dog80, how old was that book? People originally thought that DNA couldn’t hold all of the information to make a person, because it has such a simple structure. A lot of scientists thought that proteins were more likely to be the structures that store genetic information because they are so complex. This hypothesis was disproven in the early 1950s.
Dog80: The examples you’ve given are probably not the most appropriate. Eye color, for example, is determined by a fairly well-understood set of genes. Same with skin color, hair color, etc. Something like height is indirectly genetic – there are genes for growth hormones (and for all the machinery necessary for growth), and there are other genes that regulate the growth genes. The regulatory genes determine how much growth hormones are produced, so different people will produce different amounts of the hormones, and grow to different heights. (There are other factors, such as nutrition.)
Perhaps what you mean is that there is not enough information stored in DNA to explain things like, say, intelligence, or compassion. These sorts of things are partly genetic, but also depend on cultural and other external factors. Structural information, such as the shape of the hand, is not well-understood now. There are genes (e.g. Sonic hedgehog) that determine limb structure, but the details are not certain. It is possible that the vast amount of introns, or ‘junk’ DNA that does not code for proteins, contain some of the ‘missing’ information. (Most junk DNA, however, probably just protects the important stuff.)
The idea that the human genome doesn’t have enough information to fully explain humans probably results from our currently patchy understanding of human genetics. We know a lot about the genes that produce catalytic proteins, less about the genes that regulate those genes, and less still about the part of DNA that does things like determine the structure of the body or brain. It is not necessary to invoke magic or the supernatural to explain how roughly 3 billion base pairs, or 30,000 genes, can produce a human.
Actually, er, I am pretty sure it is true, AndrewT. The “extra information” comes from all sort of things, for example the environment itself. Environment helps determine cell specialization, for example, when the DNA itself cannot account for it (in a way). But it is a pretty misleading thing to say. DNA creates your body, no questions. But AFAIK, you cannot take an unspecialized cell, analyze the DNA, and say, “This will be part of the left arm.” But being part of a left arm is in the DNA.
Thanks, Roches. Raises another question though. What triggers RNA to assemble, then, if it is, as you say, chopped up and recycled?
I was responding to the claim that “there is too much information about a human body … and the DNA is too small to have all that info coded into its structure”, and I maintain I’m right about that. The problem for biology is more the reverse: why is DNA so big when it doesn’t seem to need to be?
Neither I nor the post I responded to referred to whether every single aspect of the structure and development of the body (such as the cell specialisation you refer to) was explicitly encoded in DNA.
