White contra gray matter: fMRI hemodynamic responses show similar characteristics, but differ in peak amplitude The sickle (betas) mutation in the beta-globin gene (HBB) occurs on five "classical" betas haplotype backgrounds in ethnic groups of African ancestry. Strong selection in favour of the betas allele - a consequence of protection https://viewsdirectory.com/listings13268991/detalles-ficci%C3%B3n-y-mantenimiento-de-c%C3%A1maras-de-seguridad