Question: What is the most exciting thing you have discovered so far??

Andy MacLeod answered on 14 Jun 2011:

Hi catangell. I remember your name from the chat on Monday. Another intesting question!

Most of the time when people are looking at genes, they’re looking at changes in sequence. If you imagine that DNA is a big set of instructions for telling a cell what to do, then the most common type of variation is what we call “Single Nucleotide Polymorphisms” or SNPs. ‘Nucleotides’ are the A’s G’s C’s and T’s that make up the DNA alphabet. ‘Single’ nucleotide means it just affects one of them and ‘Polymorphism’ is a change. So a SNP is a single letter that’s changed in the DNA instructions, and that can sometimes cause cells to behave differently. My colleagues have been looking at the effects of SNPs on intelligence but haven’t found any specific genes.

I’ve been looking at a different kind of genetic variation called “Copy Number Variants” or CNVs. If you think of SNPs as single-letter typos in the instruction book, then CNVs are like whole paragraphs (sometimes even chapters!) that have been deleted or copied more than usual. We normally get two copies of each gene: one from mum and one from dad. But sometimes the copying mechanism isn’t exact, so genes can be deleted (so we have 0 or 1 copy) or duplicated (so we have more than 2). If these genes give instructions that affect how intelligent you are, then we’d expect the number of gene copies to be related to intelligence measures. This is what I’ve been doing: we have intelligence test results from about 3,000 people, and I’ve looked at a whole load of genes to see what effect the number of copies have. I didn’t find much effect for most of them, but there are a couple where it looks like changes in gene count can effect intelligence. That made me pretty excited.