Does stomach Acid kill the DNA of semen?

Discussion in 'Chemistry' started by Alice in wonderland, Jun 5, 2010.

  1. Alice in wonderland Registered Member

    Messages:
    1
    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.
     
  2. GeoffP Caput gerat lupinum Valued Senior Member

    Messages:
    21,282
    After a while, yes. But it's viable for some time. A good eight hours, I thiiiiink.
     
  3. GeoffP Caput gerat lupinum Valued Senior Member

    Messages:
    21,282
    No, can't be that long. Maybe four hours?
     
  4. kmguru Staff Member

    Messages:
    11,559
    DNA is an Acid.
     
  5. Stryder Keeper of "good" ideas. Staff Member

    Messages:
    13,060
    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.
     
  6. GeoffP Caput gerat lupinum Valued Senior Member

    Messages:
    21,282
    Ah true.
     
  7. hypewaders Save Changes Moderator

    Messages:
    12,061
    Fascinating scene being conjured in this cheerful thought experiment... Geoff you can take the sample, um, I'm outta here. :puke:
     
  8. GeoffP Caput gerat lupinum Valued Senior Member

    Messages:
    21,282
    Not quite my bag, although a lot of my friends went to forensics.
     
  9. spidergoat nameless monster Valued Senior Member

    Messages:
    47,018
    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]
     
  10. Asguard Kiss my dark side Valued Senior Member

    Messages:
    23,052
    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.
     
  11. Orleander OH JOY!!!! Valued Senior Member

    Messages:
    25,822
    what would it matter. It would be in her mouth on on her teeth, right?
     
  12. John99 Banned Banned

    Messages:
    22,046
    Precisely.
     
  13. Fraggle Rocker Staff Member

    Messages:
    22,737
    This is why corpses begin to smell. The food in their stomach and intestines putrefies, generating gas.
    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.
     
  14. spidergoat nameless monster Valued Senior Member

    Messages:
    47,018
    Correct, their DNA will exist longer than they are viable as sperm.
     
  15. ScaryMonster I’m the whispered word. Valued Senior Member

    Messages:
    1,074
    Like the blood of the creature from Alien? If it were concentrated enough would it eat through metal?
     
  16. spidergoat nameless monster Valued Senior Member

    Messages:
    47,018
    No, DNA does not have an inherent pH value.
     
  17. Hercules Rockefeller voltage gated ion channel Moderator

    Messages:
    2,716
    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.


    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).
     
    Last edited: Jun 8, 2010
  18. Asguard Kiss my dark side Valued Senior Member

    Messages:
    23,052
    as i said:p (though i couldnt rember the name of the emzime for digesting DNA:p)
     
  19. Hercules Rockefeller voltage gated ion channel Moderator

    Messages:
    2,716
    Yes, poorly. :p I was expanding and clarifying. :cool:
     
  20. Hercules Rockefeller voltage gated ion channel Moderator

    Messages:
    2,716
    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.
     

Share This Page