PCR to screen for diseases

[james86]

My notes mention several times how some genetic disorders can be screened via PCR, and differentiate this technique from Southern blotting. What is the difference between these techniques; I simply thought pcr involved amplification of dna?

[JackBean]

I think, they are pretty different. Yes, PCR involves amplification of DNA

[sunghoo]

Yes you are right, but it does not simply amplify a piece of dna, in fact, it can also copy the dna . The copies can be studied or used in comparison with other original DNA samples which in return you can determine if the dna sequencing is correctly represented, and possibly, genetic disorders can show up.
Difference between the two is that PCR uses extracted bacteria called "Taq polymerase", where as southern blotting uses probe which is single-stranded DNA to indicate the sequences.

[JackBean]

quote sunghoo:

Yes you are right, but it does not simply amplify a piece of dna, in fact, it can also copy the dna .

and what is amplification?

There are plenty of Pol for PCR, some are derived from TaqPol, but many aren’t.

[sunghoo]

what do you mean what is amplification?

[JackBean]

quote sunghoo:

but it does not simply amplify a piece of dna, in fact, it can also copy the dna .

you wrote, that it does not only amplify, but also copy the DNA. So, what’s the difference?

[sunghoo]

amplification is not same as copying dna, amplification means to enlarge or make it better, where as copying means just to make another clone of dna……..

[JackBean]

well, if you amplify some piece of DNA, you make a copy, don’t you?

[sunghoo]

Right. haha I forgot about that

[james86]

Thanks alot for the replies. so having amplified the DNA, how would you screen for the genetic disorders if not via southern blotting?

Thanks

[JackBean]

that depends on what type of mutation you have. If some large indel, you can look to gel and see the size of your amplicon. If you have some 1 nt mutations (indels, exchanges), the best way is to discriminate between present/absent (you design one of your primers to the mutation. This is how are SNP examined)

[debabio]

For diagnosis 1st you have to design a primer n amplify the sequence, the amplified DNA is then sequenced and the sequence is then compared to the data base of known sequence to determine wheather it is normal or mutant,example- Sickle cell anemia, thalassemia etc.

[JackBean]

you don’t have to sequence it

[Orome]

Hey JackBean,
in Diagnostics Multiplex PCR is a standard method. See http://en.wikipedia.org/wiki/Multiplex-PCR for further information.
For example Duchenne/Becker-Muscledystrophy can be detected with this technique.
Another interesting technique is MAPH-analysis which requires PCR and probe hybridization (http://www.dmd.nl/DMD_MAPH.html).

Greets
Orome

[JackBean]

did I say something else?

[Orome]

no, i just wanted to provide some more specific information for the community 🙂

[Author]

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