Nature HapMap cover
When comparing the genetic code (the 3 billion A, C, G, and T letters) of two people, changes can be seen every one to three thousand letters. The changes are often inherited in groups, taking on a kind of "block" structure. Each difference is one of two letters (represented by the deeper and paler red colors). This image was used for the cover of the HapMap issue of the journal Nature. It was created using this project and depicts the CFTR region of the human genome, a reference to (one of?) the earliest genetic projects (localization of CFTR alleles) to grace the cover of Nature.
This image represents blocks in the genetic profile of three different populations using data collected by the International HapMap Project (hapmap.org). The top row shows a group of Yorubans from Africa, the middle row a groups with Western European Ancestry, and the final group a set of Japanese and Han Chinese individuals. Higher genetic diversity is seen with less "block" structures in each row, lower genetic diversity means more blocks. The vertical height of each column is proportional to the number of people in each group that has one group of changes or another.