[asaaal]

do you need to mark the start of the single dna strand with a MARKED DNA probe?
The terminator nucleotide strands will already be marked so we can easily identify where the dna is during electropherisis.

Whats the point in labelling the probs too?

[LSD]

(Original post by asaaal)
do you need to mark the start of the single dna strand with a MARKED DNA probe?
The terminator nucleotide strands will already be marked so we can easily identify where the dna is during electropherisis.

Whats the point in labelling the probs too?

You label the probe so you can ensure it has hybridized with the DNA sequence. If you didn't label it, you'd never know if it found it's complementary BP sequence in the sample or not. Keep in mind probes are used to find particular DNA sequences, if you can't find the probe, you can't find the sequence.

Edit: Sorry the probes are what you actually mark the DNA with, so they must be fluorescent/radioactive etc. so you can be sure they've paired on to the sample. At least when ever I've done it :s

[asaaal]

(Original post by LSD)
You label the probe so you can ensure it has hybridized with the DNA sequence. If you didn't label it, you'd never know if it found it's complementary BP sequence in the sample or not. Keep in mind probes are used to find particular DNA sequences, if you can't find the probe, you can't find the sequence.

Edit: Sorry the probes are what you actually mark the DNA with, so they must be fluorescent/radioactive etc. so you can be sure they've paired on to the sample. At least when ever I've done it :s

i understand your point for gene therapy, because youd want to find the gene youre lkooking for etc butduring DNA sequencing youre only really interested in the position of the terminator nucleotide in order to see where it is on the photographic film.. so what information does the probe provide us with for dna sequencing ?

[LSD]

(Original post by asaaal)
i understand your point for gene therapy, because youd want to find the gene youre lkooking for etc butduring DNA sequencing youre only really interested in the position of the terminator nucleotide in order to see where it is on the photographic film.. so what information does the probe provide us with for dna sequencing ?

I'm quite confused now! When you say in the first post that the terminator nucleotide sequence is already marked, isn't it the probes that do the marking? I'm not sure what else you'd need the probes for :s

[asaaal]

(Original post by LSD)
I'm quite confused now! When you say in the first post that the terminator nucleotide sequence is already marked, isn't it the probes that do the marking? I'm not sure what else you'd need the probes for :s

noooo! thats why i dont understand it and i got confused..

a probe attaches to the start of the template strand so that dna polymerase can function as it can only attach complementary nucleotides to a double strand, then as its a random process a terminator molecule gets attached but as its a terminator molecule it cannot form bonds with nucleotides either side - so sometimes the new dna will be long and sometimes short depending where the terminator nucleotide is .. what i dont understand is why does the probe need to be labelled?!