View Full Version : Does stomach Acid kill the DNA of semen?


Alice in wonderland
06-05-10, 07:44 AM
I female is murderd, her body is autopsied, the said they find dna from semen found in her stomach during the auposie,My thought is that the acid in the stomach would kill the dna in the sperm, (does the acid in the stomach kill the dna of Semen?) Thank you and I am sorry if that was to graphic.

GeoffP
06-05-10, 08:02 AM
After a while, yes. But it's viable for some time. A good eight hours, I thiiiiink.

GeoffP
06-05-10, 08:02 AM
No, can't be that long. Maybe four hours?

kmguru
06-05-10, 09:16 AM
DNA is an Acid.

Stryder
06-05-10, 09:47 AM
To be honest I think the digestive system functions when alive more than when dead. The body produces enzymes and triggers chemical reactions to deal with digesting, it can only do that while alive. (In fact it's not good to eat and then sleep on a full stomach because the digestive process is slowed)

It's possible that the death of someone would inhibit the chemical reactions, it would also inhibit how food or any other materials pass down into the stomach. Which would mean such materials might not have even made it that far.

GeoffP
06-05-10, 10:48 AM
Ah true.

hypewaders
06-05-10, 02:09 PM
Fascinating scene being conjured in this cheerful thought experiment... Geoff you can take the sample, um, I'm outta here. :puke:

GeoffP
06-05-10, 03:29 PM
Not quite my bag, although a lot of my friends went to forensics.

spidergoat
06-05-10, 03:49 PM
The normal environment of the vagina is a hostile one for sperm cells, as it is very acidic (from the native microflora producing lactic acid), viscous, and patrolled by immune cells. The components in the seminal plasma attempt to compensate for this hostile environment. Basic amines such as putrescine, spermine, spermidine and cadaverine are responsible for the smell and flavor of semen. These alkaline bases counteract the acidic environment of the vaginal canal, and protect DNA inside the sperm from acidic denaturation.[wiki]

Asguard
06-05-10, 04:35 PM
spidergoat: killing them and destroying there DNA are 2 compleatly different things

GeoffP: i cant rember what specifically digests DNA but i have a feeling that its located further down the GI tract. Pepsin breaks down protines when activated with hydrochloric acid.

Orleander
06-05-10, 06:20 PM
what would it matter. It would be in her mouth on on her teeth, right?

John99
06-05-10, 06:24 PM
spidergoat: killing them and destroying there DNA are 2 compleatly different things


Precisely.

Fraggle Rocker
06-05-10, 06:53 PM
To be honest I think the digestive system functions when alive more than when dead. The body produces enzymes and triggers chemical reactions to deal with digesting, it can only do that while alive. (In fact it's not good to eat and then sleep on a full stomach because the digestive process is slowed) It's possible that the death of someone would inhibit the chemical reactions, it would also inhibit how food or any other materials pass down into the stomach. Which would mean such materials might not have even made it that far.This is why corpses begin to smell. The food in their stomach and intestines putrefies, generating gas.
what would it matter. It would be in her mouth on on her teeth, right?We aren't told how long ago the oral sex took place. She could have brushed her teeth and used a mouthwash. If she was a hooker rather than a girlfriend she might very well have done that.

spidergoat
06-05-10, 07:16 PM
spidergoat: killing them and destroying there DNA are 2 compleatly different things
Correct, their DNA will exist longer than they are viable as sperm.

ScaryMonster
06-05-10, 10:01 PM
DNA is an Acid.

Like the blood of the creature from Alien? If it were concentrated enough would it eat through metal?

spidergoat
06-05-10, 10:07 PM
Like the blood of the creature from Alien? If it were concentrated enough would it eat through metal?
No, DNA does not have an inherent pH value.

Hercules Rockefeller
06-07-10, 08:14 PM
I female is murderd, her body is autopsied, the said they find dna from semen found in her stomach during the auposie,

The stomach will contain DNA from all the plant and animal tissue that the person has ingested. PCR analysis of DNA extracted from stomach fluid from the autopsy may reveal the presence of human DNA. It couldn’t determine specifically that it came from semen, but that would be the obvious assumption.



My thought is that the acid in the stomach would kill the dna in the sperm, (does the acid in the stomach kill the dna of Semen?)

The digestive role of the stomach is protein digestion via secretion of the protease pepsin. Hydrochloric acid secretion activates the pepsin and also serves to kill anything that’s living (bacteria, viruses, parasites etc). So the sperm would definitely be killed and degraded (being comprised of protein), but I don’t know whether the DNA released from the sperm would degrade whilst under stomach conditions. There is no specific DNA digestion process/mechanism in the stomach. DNA would undergo acid hydrolysis after a period of time, but whether that period of time is less than or greater than the emptying rate of the stomach, I don’t know.

If ingested DNA survives passage through the stomach, it will be degraded in the small intestine as pancreatic secretions contain DNases (enzymes that degrade DNA).

Asguard
06-07-10, 08:17 PM
The stomach will contain DNA from all the plant and animal tissue that the person has ingested. PCR analysis of DNA extracted from stomach fluid from the autopsy may reveal the presence of human DNA. I couldnít determine specifically that it came from semen, but that would be the obvious assumption.




The digestive role of the stomach is protein digestion via secretion of the protease pepsin. Hydrochloric acid secretion activates the pepsin and also serves to kill anything thatís living (bacteria, viruses, parasites etc). So the sperm would definitely be killed and degraded (being comprised of protein), but I donít know whether the DNA released from the sperm would degrade whilst under stomach conditions. There is no specific DNA digestion process/mechanism in the stomach. DNA would undergo acid hydrolysis after a period of time, but whether that period of time is less than or greater than the emptying rate of the stomach, I donít know.

If ingested DNA survives passage through the stomach, it will be degraded in the small intestine as pancreatic secretions contain DNases (enzymes that degrade DNA).

as i said:p (though i couldnt rember the name of the emzime for digesting DNA:p)

Hercules Rockefeller
06-07-10, 08:33 PM
as i said:p

Yes, poorly. :p I was expanding and clarifying. :cool:

Hercules Rockefeller
06-08-10, 08:00 PM
Come to think of it, the fact that we have evolved pancreatic secretions that contain DNase enzymes strongly suggests that DNA survives stomach conditions and makes it to the small intestine.

Asguard
06-08-10, 08:08 PM
Come to think of it, the fact that we have evolved pancreatic secretions that contain DNase enzymes strongly suggests that DNA survives stomach conditions and makes it to the small intestine.

probably but not nessarly, for instance it is POSSABLE that its a 2 step proccess where either slaviva or stomic contents (probably acid but it could be something else) start digestion and then its finalised into a usuable and conductable product by DNase. However i doubt it

S.A.M.
06-09-10, 07:56 AM
For Helicobacter pylori research gastric juice samples can be used to isolate the DNA. From that we can probably extrapolate that stomach acids do not destroy DNA

GeoffP
06-09-10, 07:58 AM
Come to think of it, the fact that we have evolved pancreatic secretions that contain DNase enzymes strongly suggests that DNA survives stomach conditions and makes it to the small intestine.

Maybe. How do we know it would survive the acidity? Extracted DNA, for example, doesn't do well outside fairly tight pH. Or at least not in my bloody lab, anyway.

Hercules Rockefeller
06-09-10, 07:16 PM
probably but not nessarly, for instance it is POSSABLE that its a 2 step proccess where either slaviva or stomic contents (probably acid but it could be something else) start digestion and then its finalised into a usuable and conductable product by DNase. However i doubt it

Possibly. I dunno. :shrug:

On an aside note, Iím not sure that breakdown of DNA creates ďusuableĒ products. Whilst our GI tracts may break down DNA, Iím not sure that the products of DNA digestion are actually used by humans. AFAIK our cells synthesize all of our own purines and pyrimidines. Any purines or pyrimidines that we absorb are excreted back out. (Can anyone correct me on this if Iím wrong?)



For Helicobacter pylori research gastric juice samples can be used to isolate the DNA. From that we can probably extrapolate that stomach acids do not destroy DNA

Maybe. But weíre talking about sperm cells, not H.pylori. These bacterial cells are not lysed by the stomach acid conditions, thus protecting the bacterial DNA inside the cells. I think itís safe to assume, however, that sperm cells would degrade/lyse under the same conditions and release their DNA. So the question becomes whether Ďnakedí DNA can survive stomach conditions, not DNA inside intact bacterial cells.



Maybe. How do we know it would survive the acidity? Extracted DNA, for example, doesn't do well outside fairly tight pH. Or at least not in my bloody lab, anyway.

Yeah, same here. Long-term storage of DNA definitely requires neutral pH and a buffering solution. But I suppose this discussion is concerned with whether DNA can survive high acidity within the timeframe of the emptying time of the human stomach. Whatís that, about 5 hours or so?

Asguard
06-09-10, 09:19 PM
Possibly. I dunno. :shrug:

On an aside note, Iím not sure that breakdown of DNA creates ďusuableĒ products. Whilst our GI tracts may break down DNA, Iím not sure that the products of DNA digestion are actually used by humans. AFAIK our cells synthesize all of our own purines and pyrimidines. Any purines or pyrimidines that we absorb are excreted back out. (Can anyone correct me on this if Iím wrong?)




Maybe. But weíre talking about sperm cells, not H.pylori. These bacterial cells are not lysed by the stomach acid conditions, thus protecting the bacterial DNA inside the cells. I think itís safe to assume, however, that sperm cells would degrade/lyse under the same conditions and release their DNA. So the question becomes whether Ďnakedí DNA can survive stomach conditions, not DNA inside intact bacterial cells.




Yeah, same here. Long-term storage of DNA definitely requires neutral pH and a buffering solution. But I suppose this discussion is concerned with whether DNA can survive high acidity within the timeframe of the emptying time of the human stomach. Whatís that, about 5 hours or so?

yes, the products of DNA hydrolyse (thank you for that, i was tearing my hair out trying to rember that word:p BTW it means "to split" with water not to break down, compleatly different proccess and incorect when refered to the gut:p) ARE usuable (and nessary) products




4. Digestion of Nucleic acids

Pancreatic nuclease enzymes digest nucleic acids (DNA and RNA) to nucleotides in the duodenum.
Membrane-bound nucleotidase enzymes in the epithelial cells of the ileum digest the nucleotides to sugar, base and phosphate, which are absorbed.
http://www.mrothery.co.uk/digestion/digestionnotes.htm

Hercules Rockefeller
06-09-10, 10:09 PM
BTW it means "to split" with water not to break down, compleatly different proccess and incorect when refered to the gut:p)

No, not incorrect. :rolleyes:

Hydrolysis IS the mechanism by which many organic polymers (eg. proteins, carbohydrates, nucleic acids, fatty acids) are broken down during digestion. For instance, it’s the biochemical mechanism by which peptide bonds are broken between amino acids in a protein/peptide, and it’s the biochemical mechanism by which glycosidic bonds are broken between carbohydrate molecules in a polysaccharide. Hydrolysis is catalysed by enzymes (peptidases and glycosidases, respectively, in the above examples). Without the catalytic activity of our digestive enzymes, hydrolysis as a digestive mechanism would proceed way too slowly.



yes, the products of DNA hydrolyse ….ARE usuable (and nessary) products

Asguard, you need to read more carefully. I stated quite clearly that DNA was broken down and that the breakdown products (purines and pyrimidines) were absorbed. Your link agrees with this:


Membrane-bound nucleotidase enzymes in the epithelial cells of the ileum digest the nucleotides to sugar, base and phosphate, which are absorbed.

Note that the term “base” refers to purine and pyrimidine molecules.

What I subsequently said was that after having absorbed the purines and pyrimidines I don’t think our cells actually use them in biochemical processes as our cells make all their own purines and pyrimidines. Absorbed purines and pyrimidines from ingested and digersted DNA are merely excreted back out of the body.

As I said, I’m not totally sure of this and I stand to be corrected. But your highly generalised link cannot do this one way or the other as it makes no comment on this issue.

Captain Kremmen
06-10-10, 02:05 AM
what would it matter. It would be in her mouth on on her teeth, right?

Not if she'd taken out her dentures first.

kmguru
06-10-10, 07:40 AM
aww..aww

spidergoat
06-10-10, 09:23 AM
I female is murderd, her body is autopsied, the said they find dna from semen found in her stomach during the auposie,My thought is that the acid in the stomach would kill the dna in the sperm, (does the acid in the stomach kill the dna of Semen?) Thank you and I am sorry if that was to graphic.

I vote this as creepiest post ever, especially when it's the first and only post by this member.

Asguard
06-10-10, 08:02 PM
To be honest I think the digestive system functions when alive more than when dead. The body produces enzymes and triggers chemical reactions to deal with digesting, it can only do that while alive. (In fact it's not good to eat and then sleep on a full stomach because the digestive process is slowed)

It's possible that the death of someone would inhibit the chemical reactions, it would also inhibit how food or any other materials pass down into the stomach. Which would mean such materials might not have even made it that far.

i just reread this post and i would like to disagree. The reason you produce gases when your dead is a) in the imidiate your spinkters relax releacing all the gas which is normally trapped in the GI tract and b) in the longer term because your GI tract is digesting your body. Without the constant replacement of the stomic lining for instance the stomics pepsin (activated by the hydrochloric acid) starts to digest the stomic and then the rest of the abdominal cavity. The same goes for the other digestive proccesses.

gendanken
06-12-10, 03:00 PM
I vote this as creepiest post ever, especially when it's the first and only post by this member.

Asguard-- who by the way turns out to not be cerebral palsic-- is actually a moderator and its the opening post you find creepy?


Fraggle:

We aren't told how long ago the oral sex took place. She could have brushed her teeth and used a mouthwash. If she was a hooker rather than a girlfriend she might very well have done that.
Are you implying prostitutes have good hygiene?

Stryder
06-13-10, 04:36 PM
i just reread this post and i would like to disagree. The reason you produce gases when your dead is a) in the imidiate your spinkters relax releacing all the gas which is normally trapped in the GI tract and b) in the longer term because your GI tract is digesting your body. Without the constant replacement of the stomic lining for instance the stomics pepsin (activated by the hydrochloric acid) starts to digest the stomic and then the rest of the abdominal cavity. The same goes for the other digestive proccesses.

Ah but this is the point, if you for instance swallowed a spoon and intended to digest it (this is just an example for arguments sake), it would take time and require your body to continue producing a chemical reaction for digestion.

If you died, the chemistry would stop being controlled, yes it would breakdown the persons internals however it would dialute itself with the materials. With no chemical moderation, the dilute will eventually be too weak to continue digestion.

invert_nexus
06-19-10, 11:23 PM
It's possible that the death of someone would inhibit the chemical reactions, it would also inhibit how food or any other materials pass down into the stomach. Which would mean such materials might not have even made it that far.

Why do you think you decompose?
It's the digestive tract gone mad.
Your tame little digestive bugs run wild and eat you.

Although, I suppose a point could be made that it's mostly the intestinal tract and not the stomach that contains said fauna.