Genetic and genomic technologies have come a long way since the initial studies of gene structure and expression. The study of genetics heavily relies on the idea that alleles, the versions of genes that make up a chromosome, are either recessive or dominant.
The presence of a dominant allele means that this version of the gene will be physically expressed in the human. Accordingly, when a recessive gene is present with a dominant gene, the recessive gene will be masked. However, the presence of two recessive alleles means that the gene will be expressed physically.
Image from cdc.gov
Recessive and dominant alleles are especially important to understand and analyze in terms of chronic diseases, like sickle cell. Sickle cell is a chronic condition that causes red blood cells to take on a ‘sickled’ shape, making it more difficult for the cells to carry oxygen throughout the body. Sickle cell is an inherited trait.
In fact, one in 13 Black infants are born with the sickle cell trait. However, one in 365 Black Americans live with sickle cell disease. How can that be? This is because the sickle cell trait is a recessive trait. This means that the only way that a person will show symptoms of sickle cell disease is if they have both recessive alleles.
If the infant inherits one dominant allele and one recessive allele, then that dominant allele will mask the recessive one.
Although the infant will not be diagnosed with sickle cell disease, they can still pass the trait onto their offspring. This is how two parents can both not have sickle cell disease, but have offspring that does.
Parents who are concerned that their child may either inherit the sickle cell trait or be diagnosed with sickle cell disease in the future can turn to