B-Thalessemia Hello, Mr. And Mrs. Jones.

You came to us because you each have relatives with B-thalessemia. You wanted to know what the chances were that you would have children with this disease.

The only way a baby can be born with B-thalessemia is if both parents carry the gene for it. At conception, each child receives one set of genes from each parent. Because each of you received one gene for B-thalessemia, it is possible that your children could inherit this disease. Neither of you are sick from it because you have "Thalassemia minor" -- one gene. However, each time you conceive a child, there's a one in four chance that the child will inherit a B-thalessemia gene from each of you. That child would have thalessemia major, a potentially serious form of the disease. In this disease, there are changes in the hemoglobin of the red blood cells. The cells can't carry oxygen...

So, people with Thalessemia minor were more likely to survive and reproduce. When their children inherited only one gene, they had Thalessimia minor, like their parents, and were also likely to get Malaria. However, if the child inherited a B-thalssemia gene from both parents, then the child had Thalessemia major.
Because each of you carry one B-Thalessemia gene, every time you conceive a child, that child has a one in four chance of receiving two genes, and having Thalessemia major. This means there is a three out of four chance the child will not have Thalessemia major, and a one in four chance that the child will not receive any Thalessemia genes.…