QotW: Identifying diseased genes

Deciphering the odd letters in our DNA can help us identify some health conditions...
05 April 2022


A figure rising out of a strand of DNA.



Malcolm wrote in to ask "How can we identify a disease? When looking at a sample of chromosomes, what are scientists looking for to spot a diseased gene?"



When infected with a new disease, it’s imperative for scientists to know exactly what it is in order to find the best cure for it. So how do they do it? Here to break it down to Otis Kingsman is Jocelynn Pearl from Tune Therapeutics of the Lady Scientist Podcast...

Jocelynn - When attempting to identify a disease, we have to compare two different sequences within the gene. If we think of the set of genes in someone’s chromosomes like a library of books, we can think of the hunt for a disease gene like looking for a book where an important word or sentence is different to the correct version - in this case, the transcription or translation of that gene.

Otis - Changes to the genetic sequence of a gene are called mutations. We can read these out using sequencing technology.

Jocelynn - The common way we sequence genes is by using Sanger Sequencing developed by Nobel Laureate Frederick Sanger and his colleagues in 1977. The sequence splits a gene into four base pairs of DNA, called nucleotides, represented as A, T, C, or G which stands for adenine, thymine, cytosine and guanine. Each group of 3 nucleotides is called a codon and these get translated to amino acids, the building blocks of proteins.

Otis - These proteins are the instructions for all sorts of processes within our bodies. When a disease is present, it leads to a mutation occurring in the codons in the protein.

Jocelynn - This disruption in the transcription or translation of the gene can change the function of the protein or the amount of that protein in a person. For example, in sickle cell disease, the gene that encodes  the protein ‘beta hemoglobin’ is mutated. Where there should be an “A” nucleotide, there is a “T”, and this mutated gene makes a person's red blood cells form a sickle shape so they cannot carry enough oxygen around the body.

Otis - The human genome is complex. It is like sifting through multiple libraries. As such finding these mutations can still be quite difficult. Fortunately, we have a few tools and techniques to help us.

Jocelynn - We use tools like ‘whole genome sequencing’ to find things like inherited gene mutations. We also use something called ‘genetic markers’ to conduct ‘genome-wide association studies’. These make comparisons across populations of people to understand genes that are associated with more complex diseases that might be caused by multiple factors  - things like obesity or schizophrenia. Over the years we have learned more about the genes that can cause disease, but there is still much to learn.

Otis - So Malcolm, scientists identify diseased genes by looking for mutations within the DNA sequences. If our colons aren’t correct, then it will affect the function of our proteins and lead to illnesses and problems within our body. But thanks to new technologies and developments in medicine, by identifying them we can start to figure out how to best cure it. Thank you to Jocelynn Pearl for clearing things up. Next week, we’ll be charging head first into this question from listener Barry.

Barry - “What causes degradation in electric car batteries? And what are the upcoming developments in EV battery technology?”


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