DNA Codon Table vs RNA Codon Table?

Question

[rebelCoder]

Hello smart people!

What is the point of DNA Codons (DNA Codon Table) ?

Don't we do DNA --> RNA Transcription to generate mRNA and use RNA Codon Table to do a Translation in order to generate a sequence of Amino acids?

Of Yes, what is the point of DNA Codons?

Thanks!

[GenoMax]

Most organisms use DNA as primary genetic material. There are some viruses that use RNA for their genomes.

[rebelCoder]

May I ask a related question?

Open Reading Frames: I create 6 reading frames from a DNA string and search for START - STOP codons (standard/simple stuff), but I am confused with one point: when/why/if we should use a DNA/Reverse Complement to create 6 reading frames to search in, or should we do a Transcription of both first, and search against RNA Codon Table ? And is there a case when you would need to create/search in ORFs from DNA/RevComplement vs two RNA sequences?

[cschu181]

Same as above, you'd use the DNA table only when working on the cDNA level or in case of single-exon genes. You could transcribe, but in any case other than cDNA / single-exon, this would cause intron content to be transcribed, which would then result in a mistranslated protein product (frameshifts due to the introns + extra intron content in the final product).

Edit: original comment sounded as if the DNA table itself causes mistranslation

Same as above, you'd use the DNA table only when working on the cDNA level or in case of single-exon genes, otherwise you'd get all the intron content transcribed (and ultimately translated) as well.

Answer 1

[ATpoint]

They are the same except that T is U in RNA, nothing more. If you work with DNA coding sequences, e.g. when cloning a plasmid construct that transcribes the actual spliced cDNA and you want to find amino acid codons in the sequence (or any other application on the DNA level) then you work with a DNA codon table. If you analyze RNA-seq data towards codons then you also use DNA codon table since RNA-seq involves reverse-transcribing RNA back into cDNA so we are at the DNA level again. Simply depends on the context when to use which table.