Anne Buchanan has a wonderful post over at The Mermaid’s Tale on one of my biggest pet peeves in public discussions of genetics:
I also found the Brca1 gene in one of the intervals I was looking at, the “breast cancer 1” gene. Candidate? This is one of the genes that, when mutated, is associated with high risk of early onset breast cancer. But, in spite of its name, it’s not a gene ‘for’ breast cancer. It’s a DNA repair gene, and it’s expressed in a variety of organs in the body, at various developmental stages. In the picture to the left, the darker stain in the section of mouse embryo represents Brca1 expression; it’s in the brain, the facial region, the liver, the intestine, the lungs, and so on.
And it’s bad enough to be named after a function that you only have when you’re mutated, that ignores your major purpose in life. But, here’s the height of indignity for a poor gene: the gene that sits next to Brca1 on mouse chromosome 11 is called Nbr1, which is short for “next to BRCA1” gene. What a way to go through life! This gene was first identified in the mid 1990s, and was of interest because of its chromosomal proximity to Brca1. But its function is still not known.
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These are but two examples of why identifying candidate genes for traits of interest is difficult. And, these are genes we know something about. When nothing’s known, neither where a gene is expressed or what it does, that gene can’t be considered a candidate for anything, even though it certainly does something. And that’s true for a lot of genes.
Students come into the classroom typically with a notion that genes are “for” something phenotypic (light skin, short height, curly hair, etc…). Getting students to embrace the fact that what genes are “for” is typically a gene product still many steps removed from not one, but many downstream phenotypes is a challenge, a challenge made greater by the fact that figuring out those interim steps in the process is difficult even for the professionals.
