|
|
| Author |
Message |
one_irish_rover
FemaleFirst Grand Master (1000+ Posts)
Joined: 22 Jun 2005
Posts: 1889
Location: NY, USA
|
 Posted: Tue Mar 07, 2006 7:45 pm Post subject: mtDNA |
 |
|
| MM6 wrote: |
| one_irish_rover wrote: |
it is fascinating, cellular evolution. theory of endosymbiosis: basically a larger bacterium engulfed a smaller bacterium--thus was born the first eukaryotic cell (actually, it was proto-eukaryotic). More to it than that, like you said.
kudos to us for derailing yet another thread  |
Exactly ! clever clogs- is there anything I can say that you haven't heard of ?? 
| MM6 wrote: |
| there is a small stretch about 500 bases long called the control region which as you say does not carry any codes for anything. I was mistaken about fewer mutations - what I meant was the mutations are neutral in that they dont affect anything - but b/c this stretch of mtDNA is so short its much quicker to check - and cheaper. Thats where the syrian hamsters come in - Prof Sykes had to collect the mtDNA from these hamsters to prove that the mutations in the control region were not too frantic or erratic which would make it near impossible to distinguish important signals from the incidental irrelevant changes after a few generations. |
| one_irish_rover wrote: |
| got it. but does Sykes say that mutations in the control region do not affect anything? bacause they do, more so than in protein coding regions, b/c the control region is cis-acting control element for many genes (gene networks). so, a mutuation in the control region could affect the expression of many proteins. does that make sense? |
Are you confusing the nucleus DNA with the mt DNA control region? He says that b/c the mtDNA control region does not carry the codes for anything in particular the mutations dont affect the performance of the mt enzymes- however he counters by stating that it does sometimes happen when mutations hit other parts of the mt DNA outside the control region - he goes on to describe rare neurological diseases which are caused by the mutations in genes that disable essential parts of the mt machinery - but b/c they are so damaged they dont usually survive the next generation and so die out. The control region mutationms on the other hand are not eliminated precisely b/c the control region has no specific function. They are neutral. It appears that thsi stretch of DNA has to be there in order for mitochondria to divide properly.
| one-irish-rover wrote: |
| ok, i had to remind myself that the mt genome is much much smaller than the nuclear genome, and does not exist across dozens of chromosomes, so gene networks/orchestration is not as intricate, and so mt control region is relatively tolerant of high mutation rate. there are other difference between mtNA control region and control regions in nuclear DNA....blah blah, anyway i'm following you... |
Exactly - you got it.
| one_irish_rover wrote: |
| i do. i'm not clear on how the mt control region of all these hamsters are identical. i'm going to have to think about that or you can explain it to me. the control region should differ between individuals (single nucleotide polymorphisms, at least). similar i can see, but exactly the same over thousands of years? moreover, if the control region is unimportant (as Sykes states) then this region should pick up many mutations and be passed on through generations, b/c they are meaningless, so there is no selection pressure. The thing is, they are meaningful, as I said up in that first paragraph. Mutations in control region are more meaningful than mutations in single genes, thus the control region is highly conserved across individuals (and across species). so, Sykes explained the control region incorrectly, it seems. i'm thinking out loud, i can't write all this. it's more for interactive realtime discussion. |
I dont think he explained it incorrectly. The mtDNA is passed dwon directly from the female line. This means that there is little change in the mtDNA from generation to generation, unlike nuclear DNA which changes by 50% each generation. The fertilized egg contains a mixture of the father and mother's nuclear DNA and an exact copy of the mother's mtDNA, but none of the father's mtDNA. The result is that mtDNA is passed on only along the maternal line. This means that all of the mtDNA in the cells of a person's body are copies of his or her mother's mtDNA, and all of the mother's mtDNA is a copy of her mother's, and so on. No matter how far back you go, mtDNA is always inherited only from the mother. Even though everyone on Earth living today has inherited his or her mtDNA from one person who lived long ago, it says our mtDNA is not exactly alike. Random mutations have altered the genetic code over the millennia. But these mutations are organised, in a way. For example, say that 10,000 years after the most recent common ancestor, one of the mtDNA branches experienced a mutation. From that point on, that line of mtDNA would include that alteration. Another branch might experience a mutation in a different location. This alteration would also be passed on. What would eventually end up with are some descendants who have mtDNA that is exactly or very much like that of some people's, somewhat like that of others, and by looking at the similarities and differences of the mtDNA of all of these individuals, the researchers could try to reconstruct where the branching took place. hth. |
|
|
| Back to top |
|
 |
dieselparkeast
FemaleFirst Grand Master (1000+ Posts)
Joined: 24 Nov 2005
Posts: 2759
|
| Posted: Tue Mar 07, 2006 7:47 pm Post subject: |
|
|
| Could you just repeat that again please? |
|
| Back to top |
|
|
one_irish_rover
FemaleFirst Grand Master (1000+ Posts)
Joined: 22 Jun 2005
Posts: 1889
Location: NY, USA
|
| Posted: Tue Mar 07, 2006 7:57 pm Post subject: |
|
|
Thank you for that explanation. That certain mutations in the control region woud be so detrimental that the cell would die (organism would very early in development) and not be passed down - that's the crucial concept I was forgetting.
I'm still not clear on how all syrian hamsters have the exact same mtDNA genome - very unusual...unless the species has not been around very long (you mention 10,000 yrs - is this the rate of mutation? one mutation/10,000 yrs). I'll ask about this another time--writing these tutorials is a full-time job. I should just read the damned book! |
|
| Back to top |
|
|
one_irish_rover
FemaleFirst Grand Master (1000+ Posts)
Joined: 22 Jun 2005
Posts: 1889
Location: NY, USA
|
| Posted: Tue Mar 07, 2006 7:58 pm Post subject: |
|
|
| dieselparkeast wrote: |
| Could you just repeat that again please? |
goddamn you dpe! |
|
| Back to top |
|
|
MM6
FemaleFirst Guru
Joined: 29 May 2005
Posts: 6879
|
| Posted: Tue Mar 07, 2006 9:12 pm Post subject: |
|
|
lol - he tends to write only so much which leaves the reader with questions exactly like those you have raised then a few chapters later he will pick up that thread again and it becomes clear - he is writing for a general audience as opposed to a peer-reviewed journal so it is frustrating in that respect - being made to wait for the money shot, so to speak - but he gets there - the incidentals and asides are all interesting - its worth reading but as I said its drawn out. I will have to go back and plough through the syrian hamsters example again but Im pretty sure he doesnt go into the detail you require - it does make more sense however in the context of the whole book. Leave it with me. I'll get back to you - I cant even find anything more on them the interweb which is frustrating.  Perseverence..
lol @dpe  |
|
| Back to top |
|
|
one_irish_rover
FemaleFirst Grand Master (1000+ Posts)
Joined: 22 Jun 2005
Posts: 1889
Location: NY, USA
|
| Posted: Thu Mar 09, 2006 4:40 am Post subject: |
|
|
| MM6 wrote: |
| I will have to go back and plough through the syrian hamsters example again but Im pretty sure he doesnt go into the detail you require - it does make more sense however in the context of the whole book. Leave it with me. I'll get back to you - |
 Thank you. You're very nice. |
|
| Back to top |
|
|
MM6
FemaleFirst Guru
Joined: 29 May 2005
Posts: 6879
|
| Posted: Sun Mar 12, 2006 9:36 am Post subject: |
|
|
| Im still working on the hamster question - the 10,000 years mutation rate is an example given - Im not sure it applies in all cases - Im still reading and now we're past the Romanovs and onto Roratonga and the Polynesians. Who incidentally share their rare tissue type with the Inuit. Intriguing. |
|
| Back to top |
|
|
one_irish_rover
FemaleFirst Grand Master (1000+ Posts)
Joined: 22 Jun 2005
Posts: 1889
Location: NY, USA
|
| Posted: Sun Mar 12, 2006 6:53 pm Post subject: |
|
|
I did some research on them...the Syrian hamsters - I didn't realise that was the name for the most common type. I had a hamster as a young kid. Her name was Cutie and she always escaped her cage and got in behind the walls of our house, and in the ceiling. We had to coax her out more times than I can remember. They are believed to be extinct in nature now. I had a point but I lost it, too much in head.
Native Americans share a common ancestor with modern Polynesian. That is interesting. So the common ancestor sailed to the Americas and then on to the .? Who was the common ancestor? Is it the Chinese? I'm going to see if I can find this book later and read up so I know what the hell we're talking about. |
|
| Back to top |
|
|
MM6
FemaleFirst Guru
Joined: 29 May 2005
Posts: 6879
|
| Posted: Sun Mar 12, 2006 7:34 pm Post subject: |
|
|
| So what did you find out about the hamsters? I dont know who the common ancestor was of the Inuit - Im not up to that part yet - but yeah get the book - that should make it easier to discuss. |
|
| Back to top |
|
|
upthegaryglitter
You Go Girl (100+ Posts)
Joined: 12 Mar 2006
Posts: 143
|
| Posted: Sun Mar 12, 2006 7:35 pm Post subject: |
|
|
Forget hamsters.
I think your avatars make a lovely couple. |
|
| Back to top |
|
|
MM6
FemaleFirst Guru
Joined: 29 May 2005
Posts: 6879
|
| Posted: Sun Mar 12, 2006 7:41 pm Post subject: |
|
|
| lol - they do dont they. Now join in our discussion group here. You make the teas and I'll set up the projector. Rover can swot up on hamsters |
|
| Back to top |
|
|
upthegaryglitter
You Go Girl (100+ Posts)
Joined: 12 Mar 2006
Posts: 143
|
| Posted: Sun Mar 12, 2006 7:46 pm Post subject: |
|
|
| What, with a name like upthe garyglitter, you want me to handle mugs that you will drink out of. |
|
| Back to top |
|
|
MM6
FemaleFirst Guru
Joined: 29 May 2005
Posts: 6879
|
| Posted: Sun Mar 12, 2006 7:48 pm Post subject: |
|
|
| lol - ok you just sit there in the gimp mask and I'll get the straitjacket. Rover help me out here. |
|
| Back to top |
|
|
one_irish_rover
FemaleFirst Grand Master (1000+ Posts)
Joined: 22 Jun 2005
Posts: 1889
Location: NY, USA
|
| Posted: Sun Mar 12, 2006 7:59 pm Post subject: |
|
|
| upthegaryglitter wrote: |
| What, with a name like upthe garyglitter, you want me to handle mugs that you will drink out of. |
who is gary glitter anyway? i can't be bothered looking him up. is he related to that other old fart you were going on about, I forget his name, Sir Jimmy Saville, or is it Timmy. |
|
| Back to top |
|
|
MM6
FemaleFirst Guru
Joined: 29 May 2005
Posts: 6879
|
| Posted: Sun Mar 12, 2006 8:01 pm Post subject: |
|
|
| Gary Glitter has just been convicted of paedophilia in Thailand. He was a 70's popstar. (ugly) |
|
| Back to top |
|
|
|
Site Map
FAQ
Usergroups
Search
Log in to check your private messages
Log in
Register
My Profile Space
