These studies are now being done by GWAS in 2 patient groups, examining both baseline HbF and the HbF response to hydroxyurea. Genetic modulation of sickle cell disease: Homozygosity for a single Î²-globin gene mutation (HBB; glu6val) causes sickle cell anemia.hese studies are now being done by GWAS in 2 patient groups, examining both baseline HbF and the HbF response to hydroxyurea. Genetic modulation of sickle cell disease: Homozygosity for a single Î²-globin gene mutation (HBB; glu6val) causes sickle cell anemia.
Spiral Galaxies. Spiral galaxy M100. Spiral galaxies have three main components: a bulge, disk, and halo (see right). The bulge is a spherical structure found in the center of the galaxy. This feature mostly contains older stars. The disk is made up of dust, gas, and younger stars. The disk forms arm structures.
In doing so, two main categories of galaxies were created-spiral and elliptical. Unlike a spiral or elliptical galaxy, irregular galaxies lack a distinct structure or shape. They are thought to make up about a quarter of all galaxies. Most irregular galaxies were once spiral or elliptical galaxies but were deformed by disorders in gravitational pull. Irregular galaxies contain large amounts of hydrogen that, in some cases, indicates new star formation.