ABOVE: Agouti Viable Yellow mice share the same DNA sequence, but have different methylation patterns.
WIKIMEDIA COMMONS, RANDY JIRTLE AND DANA DOLINOY
Brown and yellow mice nestle side by side in their cages in Anne Ferguson-Smith’s molecular genetics lab at the University of Cambridge. The mice are Agouti Viable Yellow, naturally occurring mutants, which, though genetically identical, have coats that vary in color—a phenomenon that researchers have long studied as an example of epigenetic inheritance.
All of the mutant mice have a gene, Agouti, that influences coat color, and an adjacent transposable element—a DNA sequence that can move about the genome, creating or reversing mutations—that promotes the gene’s expression. In the brown mice, this element is methylated and, therefore, silenced. But in the yellow mice, it isn’t methylated, meaning that these animals overexpress Agouti signaling protein in many tissues, leading to their yellow hue.
Importantly, Ferguson-Smith says, yellow mother mice tend ...
