Beta gene not needed
Newborns have fetal hemoglobin, not adult hemoglobin, in their red blood cells.
major babies look normal at birth because fetal hemoglobin doesn't need beta globulin from the beta genes. As fetal hemoglobin goes away after birth and adult hemoglobin starts being made, the baby will feel the effects of his lack of beta globulin. Symptoms start after the first 6-8 months of life.