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syph3r2001
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Joined: 01 Jul 2003
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 Posted: Thu Nov 25, 2004 11:46 pm Post subject: Biology: DNA |
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If an incorrect nucleotide is incorporated into a forming strand of DNA, will this mistake be transmitted to the next generation of DNA molecules that forms from this strand?
I assume yes, because all generations are identical. I just wonder if the DNA would replicate at all, since its deformed? |
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Quantum_
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Joined: 07 Nov 2004
Posts: 11
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| Posted: Fri Nov 26, 2004 12:01 am Post subject: |
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Well, this is how mutations take place. But overall this is caused by cosmic rays, and so is small, predictable, and regular. As my dad used to say when I was in elementary school (early '60's), beta and gamma particles are passing through us all the time, but they are so small as to have little if no effect. But alpha particles are massive, and so do the genetic damage, as far as we can tell. Fortunately are not so common.
Now, when a mutation is too significant, the organism dies.
I used to tease my little brother: they've just figured out how to open up and clone DNA by washing enzymes over it. And, when you eat chicken, you're actually washing over it with enzymes. And so, aren't you concerned that you are turning into a chicken?
Amazingly, he's turned out to be quite a normal adult, in spite of me... |
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littlebuddy
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Joined: 11 Jul 2003
Posts: 35
Location: Boulder, CO, USA
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| Posted: Fri Nov 26, 2004 9:21 am Post subject: Re: Biology: DNA |
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| syph3r2001 wrote: | If an incorrect nucleotide is incorporated into a forming strand of DNA, will this mistake be transmitted to the next generation of DNA molecules that forms from this strand?
I assume yes, because all generations are identical. I just wonder if the DNA would replicate at all, since its deformed? |
Yes, the mistake will be transmitted. Almost all organisms lack error-detecting abilities when it comes to DNA replication and gene synthesis. The only exception might be some types of ciliates, but I'm only familiar w/ their gene synthesis processes, not the DNA replication processes. |
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PseudoMon
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Joined: 26 Nov 2004
Posts: 0
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| Posted: Fri Nov 26, 2004 11:48 pm Post subject: Re: Biology: DNA |
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| syph3r2001 wrote: | If an incorrect nucleotide is incorporated into a forming strand of DNA, will this mistake be transmitted to the next generation of DNA molecules that forms from this strand?
I assume yes, because all generations are identical. I just wonder if the DNA would replicate at all, since its deformed? |
Every DNA molecule consists of a two paired strings of nucleotides. There are 4 different nucleotides: A, T, C and G. A matches T, C matches G.
So for example a small piece of DNA could be something like:
...ATCTCGATCGGGTCA...
...TGCAGCTAGCCCAGT...
Only a lot longer (a human cell has 46 DNA molecules and a total of about 6*10^9 nucleotides).
If the above sequence suffers a mutation (say in its 3rd nucleotide):
...ATCCCGATCGGGTCA...
...TGCGGCTAGCCCAGT...
I would not call it "deformed" - it just encodes a different sequence.
DNA will be able to replicate pretty much independently of its sequence except if a few critical regions called origins of replication (where the DNA replication starts) are messed up. In fact, we all have slightly different DNA sequences (that's the reason we are not identical) and our DNAs get replicated all right anyway.
Even if the mutation happened within the origin of replication, it may not be bad enough to stop it from working. Even if it did stop if from working, many organisms (like humans) will have several origins of replication in each DNA molecule, so the DNA would still get replicated from the other ones.
So the answers are:
Yes, it will be transmitted.
Yes, it will replicate - except in very rare instances.
You can check out the following link if interested:
link
Mod Edit: fixed links - tomk
It's a chapter of the free online version of Alberts' Molecular Biology of the Cell, the "bible" of molecular biology.
| littlebuddy wrote: | | Almost all organisms lack error-detecting abilities when it comes to DNA replication and gene synthesis. |
Not quite right...
In fact, most organisms have developed a range of strategies both to prevent the introduction of errors during DNA replication, and to repair them once they have happened.
It is estimated that human cells are able to correct 99.9% of mutations.
You can read more about this again in Alberts:
link2
Hope that's helpful. |
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PseudoMon
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Joined: 26 Nov 2004
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| Posted: Fri Nov 26, 2004 11:52 pm Post subject: Re: Biology: DNA |
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| PseudoMon wrote: | | Yes, it will be transmitted. |
Should actually read:
Yes, it will be transmitted - unless it gets corrected (which will be in most cases). |
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Quantum_
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Joined: 07 Nov 2004
Posts: 11
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| Posted: Sat Nov 27, 2004 3:28 am Post subject: |
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PM, do you happen to know whether any progress has been made on stopping telemeric shortening?
I've stopped protein glycation, using aminoguanidine, but would like to live forever if possible. There was a very
promising compound (called something like ACT25), but I haven't heard any news for a couple of years.
PS - please split your links, or bury them in a word, so the page width goes back to normal. |
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Dr Gonzo
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Joined: 31 Jan 2004
Posts: 276
Location: Austin, TX
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| Posted: Sat Nov 27, 2004 3:40 am Post subject: |
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| Quantum_ wrote: | | Well, this is how mutations take place. But overall this is caused by cosmic rays, and so is small, predictable, and regular. As my dad used to say when I was in elementary school (early '60's), beta and gamma particles are passing through us all the time, but they are so small as to have little if no effect. But alpha particles are massive, and so do the genetic damage, as far as we can tell. Fortunately are not so common. |
No. Any form of ionizing radiation can cause mutations if it interacts with the chemical bonds in the DNA molecule by knocking off electrons (ionizing them). Alpha, beta, and gamma particles can do this. Cosmic rays are made of muons, which are more weakly ionizing, mostly because they're traveling fast. Alpha particles are massive enough that they don't penetrate the outer layer of dead skin on your body. They're only really harmful if they are somehow taken internally -- for instance, if you breathe a gas that contains some kind of alpha emitter. Betas (actually electrons ejected from atomic nuclei) are also ionizing and penetrate deeper. Gammas are electromagnetic radiation like visible light, radio, x-rays, etc. They are much higher energy (higher frequency) light. They can cause cellular damage. Also DNA damage.
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"Families is where our nation finds hope, where wings take dream."
George W. Bush |
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Quantum_
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Joined: 07 Nov 2004
Posts: 11
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| Posted: Sat Nov 27, 2004 3:47 am Post subject: |
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Hey man, my info is 40 years old...
Best I could offer. |
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paladin-zero
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Joined: 19 May 2004
Posts: 322
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| Posted: Sat Nov 27, 2004 4:28 am Post subject: |
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| docGonzo2000 wrote: | | Any form of ionizing radiation can cause mutations if it interacts with the chemical bonds in the DNA molecule by knocking off electrons (ionizing them). Alpha, beta, and gamma particles can do this. Cosmic rays are made of muons, which are more weakly ionizing, mostly because they're traveling fast. Alpha particles are massive enough that they don't penetrate the outer layer of dead skin on your body. They're only really harmful if they are somehow taken internally -- for instance, if you breathe a gas that contains some kind of alpha emitter. Betas (actually electrons ejected from atomic nuclei) are also ionizing and penetrate deeper. Gammas are electromagnetic radiation like visible light, radio, x-rays, etc. They are much higher energy (higher frequency) light. They can cause cellular damage. Also DNA damage. |
Sometimes there is a modification of DNA through ionization/radiation, where two neighboring bases on the same strand, of the same type (I think C, but I dont remember for sure), actually bind together, causing a pucker in the structure. Its a problem during the translation of DNA to RNA, because there is a protein that unzips the DNA, and it gets stuck at these puckers. I think I remember learning that this is one cause of skin cancer.
It is difficult, near impossible, for a base substitution to occur at any time except during cellular mitosis, when the DNA is actually replicated. If a mutation does occur there, one base pair would mean changing one peptide in a protein, and I cant think of a protein that derives its function from any one peptide. Function is usually based on the tertiary structure which is not strongly effected by a change of this kind. If the sequence coding the beginning or the end of the gene was mutated, I could imagine that would be a bigger problem, but I have never read anything about this case.
One last point is that mutations occur frequently in living systems, without radiation. A scientist, studying corn, won a Nobel for the discovery a few years back. She observed the sections swapping from one arm to another on a single chromosome. |
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Dr Gonzo
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Joined: 31 Jan 2004
Posts: 276
Location: Austin, TX
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| Posted: Sat Nov 27, 2004 7:24 am Post subject: |
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Thanks, paladin, I didn't know that. I just know the physics side -- that's my field. 
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"Families is where our nation finds hope, where wings take dream."
George W. Bush |
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Dr Gonzo
Apprentice
Joined: 31 Jan 2004
Posts: 276
Location: Austin, TX
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| Posted: Sat Nov 27, 2004 7:28 am Post subject: |
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PseudoMon, when you're putting in url's, do it like this: | Code: | | [url=http://www.foo.bar]link text[/url] |
please. When you put long url's inline in the text, it stretches the thread way out sideways. It's just cleaner too. Thanks.
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"Families is where our nation finds hope, where wings take dream."
George W. Bush |
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PseudoMon
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Joined: 26 Nov 2004
Posts: 0
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| Posted: Sat Nov 27, 2004 9:16 pm Post subject: |
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| Quantum_ wrote: | | PM, do you happen to know whether any progress has been made on stopping telemeric shortening? |
Nope.
Sorry all about the links thing, and thanks for explaining how to do it right. |
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