Question about DNA

isnt it going to be difficult for the mitochondria and the cell in which it is present if its DNA actually moved into the nucleus......then the nucleus would have to synthesise prokaryotic as well as eukaryotic ribosomes.....which might lead to complications...
so could u plz give me ideas on how this could take place?
 
Well, mitochondrial ribosomes are still synthesized, for the most part, in the mitochondrion to translate the genes still remaining in the mitochondrial genome. However, as far as the complications of synthesizing prokaryotic genes in a eukaryote, the only real difficulty would be in attaching the prokaryotic gene to a eukaryotic promoter in order for the gene to be transcribed. Prokaryotic genes contain none of the weird things that our genes do - like glycosylation signals, introns, etc. But all the proteins destined to work in the mitochondrion have a short "bar code" or signal sequence that tells the cellular protein-making machinery to send those proteins to the mitochondrion.
There are very good reasons for the proto-mitochondrion to live in eukaryotes - free food and protection in exchange for doing the eukaryotes' oxidative respiration (breathing oxygen for us). However, in no other situations that I am aware of (except for chloroplasts, and that's pretty much the same thing), has a symbiote actually given up most of its' genome to the other partner in the symbiotic relationship.
 
swetha said:
i found some info about DNA that can be taken up by the intestinal lining......and that alll of the DNA is NOT degraded
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=19622
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That’s an interesting find, swetha – thanks! :) I read through it and a few things came to my mind:

First, I am a little puzzled as to why they used M13mp18 DNA. They state that “phage M13mp18 DNA as a test molecule devoid of homology to mouse DNA”, so it would appear that they chose it because it is sufficiently different to mouse DNA that they can detect minute copies of it by FISH analysis in whole cells. But in my experience it is possible to detect the DNA of ‘higher’ organisms than a phage by this analysis. I’ve detected a single copy of an EGFP transgene by FISH analysis of a chromosome spread. That’s a jellyfish gene which is closer to a mouse than a bacterial phage is. So why they didn’t try this experiment with a more relevant DNA test molecule (ie. something that a mouse might actually eat in a normal diet) I do not understand. Some sort of plant test DNA molecule, maybe? I would have thought that plant DNA could be discriminated from endogenous mouse DNA by FISH and PCR. I’m left wondering whether or not this is some sort of artificial artifact that is specific to the M13mp18 DNA, especially as the references they used as the basis of their experiments where adenoviral DNA uptake in cell culture – ie. another virus.

Second, M13mp18 is a bacterial phage. I expect that our digestive epithelium would be exposed to minute quantities of this DNA, yet the experimental protocol was to feed huge quantities of this DNA into the mouse – multiple doses of 50ug. I imagine that would be roughly equivalent to a lifetime’s exposure to this viral DNA in one go. Once again, it raises the question of whether or not this is some sort of artificial artifact that is specific to the M13mp18 DNA.

Third, the FISH images are terrific, but I think they just go to show what was said during the course of this thread. People choose their best images for publication, so we can assume that these are their best results. What we see in each panel is a tiny amount of phage DNA in a single cell after having been fed unnatural quantities of the DNA. To me this merely supports what was said above by a couple of different people: uptake of DNA by the digestive epithelium doesn’t happen often, but it can happen. <P>
 
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zyncod said:
Well, mitochondrial ribosomes are still synthesized, for the most part, in the mitochondrion to translate the genes still remaining in the mitochondrial genome. However, as far as the complications of synthesizing prokaryotic genes in a eukaryote, the only real difficulty would be in attaching the prokaryotic gene to a eukaryotic promoter in order for the gene to be transcribed. Prokaryotic genes contain none of the weird things that our genes do - like glycosylation signals, introns, etc. But all the proteins destined to work in the mitochondrion have a short "bar code" or signal sequence that tells the cellular protein-making machinery to send those proteins to the mitochondrion.
There are very good reasons for the proto-mitochondrion to live in eukaryotes - free food and protection in exchange for doing the eukaryotes' oxidative respiration (breathing oxygen for us). However, in no other situations that I am aware of (except for chloroplasts, and that's pretty much the same thing), has a symbiote actually given up most of its' genome to the other partner in the symbiotic relationship.
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i found a little info on transfer of a few genes that do take place from the mitochondria to the nucleus....this seems to happen more often in the plants

www.bios.niu.edu/duvall/bios439/Period12.pdf
 
This is not entirely relevant, but poses a similar question. I was told today that antibodies can be passed from mother to baby through breast milk - but would these not be all digested in the baby's stomach? And even if there were some left, surely the baby's body wouldn't let foreign antibodies enter it's system, right? I asked my teachers this, and they had no answer. Can anyone help?
 
darkbutterfly said:
I was told today that antibodies can be passed from mother to baby through breast milk - but would these not be all digested in the baby's stomach? And even if there were some left, surely the baby's body wouldn't let foreign antibodies enter it's system, right?
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I believe the principal antibody supplied via breast milk is the IgA type. It is believed that the primary functional role of IgA antibodies is to protect epithelial surfaces from infectious agents, just as IgG antibodies protect the extracellular spaces of the internal tissues. IgA antibodies prevent the attachment of bacteria or toxins to epithelial cells of the gut and the absorption of foreign substances, and provide the first line of defense against a wide variety of pathogens. Newborn infants are especially vulnerable to infection, having had no prior exposure to the microbes in the environment they enter at birth. IgA antibodies are secreted in breast milk and are thereby transferred to the gut of the newborn infant, where they provide protection from newly encountered bacteria and viruses until the infant can synthesize its own protective antibodies. IgA antibodies have evolved to be resistant to degradation by digestive proteases and acids.

<I><B>Source</B>: Immunobiology (5th Ed) by Janeway, Travers, Walport and Shlomchik.</I><P>
 
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