Every human has a couple of genes that will be separated when they make gametes. A baby will get one gene from each parent (one sperm and one egg).
Sickle cell gene is inherited by an autosomal recessive pattern, which means you need both defect genes to get the disease. The person with 1 defect gene can survive and live like normal. This person called a carrier because they carry one defect gene.
Someone that carries one defect gene can come as a result if you cross normal or carrier genotype (AA/Aa) with a carrier(Aa), or with homozygote recessive that carries 2 defect genes (aa). The person will get one healthy gene from the first parent with normal genes, and one defect gene from the second parent.
