How do scientists read DNA sequences?

Question

I’ve been watching some videos about DNA and came across a DNA sequence with a bunch of letters for a virus. How do scientists read them or make sense of them? Can they tell what a virus/or DNA will do or how it will work, just from the sequence?

In: 5

Answer 1

DNA sequences consist of 4 nucleic acid residues – these are just simple molecules – and they are abbreviated by four letters: atgc.

Those letters can encode proteins, which do a lot of the chemical work that makes up what we think of as life. The atgc letters encode each subunit of a protein (an amino acid residue) by their arrangement in triplets such as acc, tca, ccc – each of these triplets are called codons.

So, if you want to read a coding sequence, you can manually start looking at the sequence until you see a “start” codon (atg) and then just roll down the line a codon at a time until you get to the end. The end is encoded by a “stop” codon. You then look at all of the amino acid residues in sequence to figure out what the encoded protein is by comparing it to other known protein sequences. If it does not match anything, then you have to do a ton of work to figure out if the protein is actually made by the organism and then what it does. You can usually get at least some idea of basic function just by looking at the sequence.

Now, that is just what is called coding sequence. There is a whole lot of DNA around and within coding sequences and the analysis of those sequences is much, much more complex. This “non coding” sequence may regulate gene expression, contribute to the physical structure of the genome or maybe not do much of anything. The best ways to analyze this information these days is by using special software that looks for certain sequences or patterns.

You mentioned viral DNA. A viral genome is almost always arranged with high efficiency and has complex gene regulation. An expert in viral genomes can quickly identify the majority of coding sequences in a viral genome, but figuring out the nuances of gene regulation and protein function can take years.

I hope this helps.