Question:
Which strand of DNA is transcribed into mRNA?
Snicker Queen
2013-02-22 14:53:03 UTC
How do you tell which strand of DNA is transcribed into mRNA? Here is an example I was trying to figure out, but I would also like to know how to differentiate the two.
5' A T G T T T T C G A C G T G C G A T T G A 3'
3' T A C A A A A G C T G C A C G C T A A C T 5'
Seven answers:
?
2013-02-22 22:31:00 UTC
> How do you tell which strand of DNA is transcribed into mRNA?



You look for a Pribnow box or TATA box or similar consensus sequence.

http://en.wikipedia.org/wiki/Pribnow_box



I don't see one up there, so...

Look for an open reading frame instead.

http://en.wikipedia.org/wiki/Reading_frame#Open_reading_frame

Yup. I see a 5'-ATG-3' sequence. The strand that has the 5'-ATG-3' "DNA codon" is the sense strand. (You're just going to have to assume there's a Pribnow box or TATA box upstream from it.)



Now, you wanted the transcribed strand, rather than the sense strand, so the strand you want is this one:

3' T A C A A A A G C T G C A C G C T A A C T 5' (antisense strand DNA)



Have a nice day.
DNAunion
2013-02-22 16:57:42 UTC
Our alleged biology professor at Harvard got it all wrong.





The template strand of DNA is read in the 3' to 5' direction. The newly synthesized RNA strand is formed in the 5' to 3' direction; it runs in the opposite direction of the template strand. Hence, if the newly synthesized strand is synthesize in the 5' to 3' direction, the template strand is read in the 3' to 5' direction.



And contra another of his claims, the coding strand is not the strand that gets transcribed into RNA, the template strand does. The DNA strand that is not transcribed is called the coding strand because, except for DNA having T and RNA having U, that DNA strand's sequence is the same as the primary RNA transcript's sequence, since they are both complementary to the template strand.





You don't have to take my word for it (even though unlike our person who doesn't know biology but claims to be a professor from Harvard, I actually do have a degree in biology), here's an undergrad cell biology text confirming what I said ...



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“(1) In contrast to DNA replication, where both DNA strands are copied, only one of the two DNA strands – the template strand – serves as a template for mRNA formation during transcription. The nontemplate DNA strand, although not directly involved in transcription, is by convention called the coding strand because it is similar in sequence to the single-stranded mRNA molecules that carry the coded message. … During DNA replication the base A pairs with T, whereas in transcription the base A pairs with U. Hence the sequence of the mRNA molecules is not exactly the same as the DNA coding strand, in the mRNA contains the base U anywhere the coding DNA strand has the base T.



And since mRNA molecules are synthesized in the 5’ -> 3’ direction (like DNA) ...



The enzyme [RNA polymerase] moves along the template DNA strand from the 3’ toward the 5’ end. Because complementary base pairing between the DNA template strand and the newly forming RNA chain is antiparallel, the RNA strand is elongated in the 5’ -> 3’ direction as each successive nucleotide is added to the 3’ end of the growing chain.”



(The World of the Cell: Seventh Edition, Wayne M. Becker, Lewis J. Kleinsmith, Jeff Hardin, and Gregory Paul Bertoni, Pearson / Benjamin Cummings, 2009, p653, 654, 657, 659)

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It would be nice if people who don't know what they are talking didn't answer - then people who asked questions wouldn't be misled.



It would be even nicer if people who don't know what they are talking about didn't lie and claim to be professors at Harvard, which makes the question askers even more convinced of the correctness of information that is wrong.









Now that I had to spend all of that to refute a liar, let's get back to your actual question.





The thing is, you can't tell which is the template strand and which is the coding strand; there's not enough information. But we can make an educated guess.



1) The template strand is read in the 3' -> 5' direction. Since this is just an example, the teacher is probably not making it difficult. It would be easier to work with if the bottom strand were the template strand.



2) The first DNA triplet in the bottom strand would make the mRNA codon AUG, which is the start codon.



So it makes sense that the bottom strand is the template strand that is transcribed into mRNA.
Kyle
2014-02-11 17:43:21 UTC
I'm sure you are long done with this course, but for the others out there this is a super tricky question. I am also working on this problem and have figured it out. Assuming it is the same question and looking at the base pairs it looks to be the same. In the question it mentions that this has a 5 protein sequence. The only possible combo that gives a 5 protein sequence is the top strand that is orientated in a 5' <- 3' direction.



The KEY is that it must be read from right to left!!! Totally screwed me up for a day or two. Once you realize the correct orientation is read from right to left you can conclude that the top strand is the anti-sence strand which is being transcribed and has the complementary mRNA strand attached in the

3' <- 5' direction . giving you the 5 protein sequence (read right to left) Stop-Pro(5)-Isl(4)-Glu(3)-Leu(2)-Met(1 start) and a Tyr that can be ignored.



The bottom strand is your sense
Peter
2013-02-24 06:21:20 UTC
Yeah, DNA... is right our professor taught us that during transcription the DNA strand that is translated is the template strand which is 3'-5' and not the coding strand which is 5'-3', also a trick is that mRNA strand is similar to the coding strand except for thymine which is transcribed as uracil
2016-10-15 03:01:11 UTC
Transcribed Dna
2016-04-11 16:48:21 UTC
For the best answers, search on this site https://shorturl.im/av08W



Why is only one strand of DNA transcribed into mRNA? B. Because transcribing both DNA strands would produce different amino acid sequences.
Genius
2013-02-22 15:02:11 UTC
Since the template DNA strand is read from 5' to 3', then that is what we call the "original" strand, or the strand we already had. The 3'-5' strand is the coding strand, or what is going to be transcribed into mRNA.



So recap,

5'-3': template strand of DNA

3'-5': coding strand of DNA, or the one that'll be transcribed into any type of RNA.


This content was originally posted on Y! Answers, a Q&A website that shut down in 2021.
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