DNA code

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leeroykincaid
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DNA code

Post by leeroykincaid » Thu Mar 29, 2018 3:27 pm

I work as a highschool teacher and I believe that in most highschool textbooks in my country there is a lost-in-translation problem involving some molecular biology basics. It has spread to the point one starts to doubt his basic knowledge, so here it goes:

For example, let's say that a triplet in mRNA is:
5' AUG 3'

That triplet is named CODON. (no problem there)

The DNA that corresponds to it has two strand.
One is coding or sense strand and contains the corresponding triplet 5' ATG 3'
The other is non-coding or antisense strand and contains the triplet 3' TAC 5'

Highschool textbooks in my country say that the triplet 3' TAC 5' , therefore the non-coding strand, is the CODE.
It makes no sense to me whatsoever, but I'd like to check it out since in English literature the term code is rarely used anyway and genetic code is usually presented as codons. Sometimes, when the list of DNA triplets is given (and it's always in 5'->3' direction since the information is read that way) it says "DNA codons".
So, to sum it up - is the DNA CODE equal to triplets in the coding or the non-coding strand?

Thanx in advance!

claudepa
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Re: DNA code

Post by claudepa » Sat Mar 31, 2018 2:35 pm

For the two strands of DNA I use the designation Watson strand and Crick strand. Watson strand has the same sequence than mRNA (sense strand). Therefore mRNA is synthetized in the cell by adding bases complementary to the Crick strand (antisense strand). So the strand which is operational (I mean used by RNApol2 to make mRNA) for the mRNA synthesis is the Crick strand. But the strand which has the same sequence than mRNA (complementary to the Crick strand) and therefore where the code can be read is the Watson strand.
I do not know if you teach in highschool (I used to teach in University) that both strands can sometimes be Watson strands. And sometimes mRNAs synthetized by both strands are therefore complementary and can be used for regulation of gene expression. This was discovered around 40 years ago in bacteria by Inouye.

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