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  #1  
Old 08-12-2012
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DNA Gene Sequencing Gel

An investigator wants to sequence part of the exon to the HFE gene known to contain a mutation associated with hemachromatosis. Using a primer that binds to a 3' flanking region on the coding strand to initiate replication of HFE gene and radiolabeled dideoxynucleotides to terminate synthesis, he obtains the results shown on the sequencing gel below.

Gene Sequencing Gel-hfe.png
Click image to enlarge

Which of the following is the sequence of the HFE gene in this region?

A. ACGACGTTACTGTC
B. CTGTCATTGCAGCA
C. GACAGTAACGTCGT
D. TGCTGCAATGACAG
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Old 08-12-2012
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Default my answer

B. Ctgtcattgcagca
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Old 08-12-2012
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Originally Posted by Casandra View Post
B. Ctgtcattgcagca
cn u xplain pls???
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Old 08-12-2012
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Default sequence

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Originally Posted by sruthi View Post
cn u xplain pls???
Ya when i first read this question i was confused too but its a simple concept asked in a twisted manner.

from this gel sequencing
Primer sequence would be 5'--TGCTGCAATGACAG--3'
and so the coding sequence would be complementary and anti-parallel to primer.
3'--ACGACGTTACTGTC--5'
AND as you remember mostly we write sequence in 5'--3'.
So answer will be 5'--CTGTCATTGCAGCA--3'

Official answer is written on more weird way. So if you guys don't agree with my explanation then i will type that whole thing tonight.
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Old 08-12-2012
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How do you get the sequence from the gel ??
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Old 08-12-2012
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Never mind I figured it out
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Old 10-23-2013
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Never mind I figured it out

aman J, can you please explain how did u figure it out?? im not gettin this question at all
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Old 10-23-2013
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Originally Posted by abeer View Post
aman J, can you please explain how did u figure it out?? im not gettin this question at all
Do this, Get a pen and a paper. Now, open that sequencing gel result image.
You start your reading from the bottom and progress to the top.
Notice the letters on the top G A T C and the dashes or lines that are under each letter.
Take this for an example, if you were blind and those dashes or lines were raised a little so u can feel them with your fingers. And if you were to run your finger on those dashed lines starting from the bottom and going to the top .. which dash or line would you hit first?
In this case, The dash or line that you would hit first would the the one that falls under the letter T.. so now write T on you paper. Continue on reading from bottom to top direction and the next dash or line you would hit or read would be the one that falls under G and then C and so on...

I'm not too good with explaining things so I might've ended up confusing you even more.. If so, my apologies.
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Old 10-23-2013
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Quote:
Originally Posted by futuredoc1987 View Post
Do this, Get a pen and a paper. Now, open that sequencing gel result image.
You start your reading from the bottom and progress to the top.
Notice the letters on the top G A T C and the dashes or lines that are under each letter.
Take this for an example, if you were blind and those dashes or lines were raised a little so u can feel them with your fingers. And if you were to run your finger on those dashed lines starting from the bottom and going to the top .. which dash or line would you hit first?
In this case, The dash or line that you would hit first would the the one that falls under the letter T.. so now write T on you paper. Continue on reading from bottom to top direction and the next dash or line you would hit or read would be the one that falls under G and then C and so on...

I'm not too good with explaining things so I might've ended up confusing you even more.. If so, my apologies.
yeah i dont understand what you are saying at all, i'm sorry
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Old 10-23-2013
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Originally Posted by CisternaChyli View Post
yeah i dont understand what you are saying at all, i'm sorry
Read the bands like you're climbing a ladder. Document the letter above that correlates with it as you climb your way up. When you finish the sequence, just write the complementary sequence and read it in reverse. You'll see the answer above.
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Originally Posted by Mo-tongji View Post
Read the bands like you're climbing a ladder. Document the letter above that correlates with it as you climb your way up. When you finish the sequence, just write the complementary sequence and read it in reverse. You'll see the answer above.
okay but which band to start with?, do we start with the left side first because as we know, we have to read from 5-3...
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Originally Posted by CisternaChyli View Post
okay but which band to start with?, do we start with the left side first because as we know, we have to read from 5-3...
Read the bands not the letters, the lowest band correlates with T, then the second lowest is G...and so on.
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