Learn About Dominant and Recessive Genes

Host: We use the terms at times recessive and dominant, what do you mean by that. Lakshmi Mehta: Okay, recessive and dominant is now referring to problems at the gene level. So we are talking about the pairs of genes that we carry. All the genes are in pairs, some genetic abnormalities are caused when one of the pair of genes doesn't work, that's called a dominant gene. So for example, you have Marfan Syndrome, it's dominant gene, because if you have two copies of the Fibrillin gene and one copy is not working it's enough to give that person problems, despite the normal copy, so that's dominant. Then you have another way that genes cause problems and that's if both the copies of the genes pair are not working, so that is called recessive. When you have recessive disease say for example, Cystic Fibrosis or Thalassaemia or Sickle cell Anemia, these are recessive gene disorders. The individual with the problem has two copies -- both copies of the gene, doesn't carry not working. Host: So both the mother and the father have to carry this way. Lakshmi Mehta: Exactly, so those two genes that are not working, didn't just pop-up out of the blue, they came one from each parent. So the parents, they are carriers. Host: And the risk of offspring is one in four. Lakshmi Mehta: Right, the risk for that couple to have more children with the same problem is one in four in every single pregnancy. It's like tossing a coin and there is also the three-fourth chance that they may not have the child with problems. Host: You could have ten kids and not have it either. Lakshmi Mehta: Exactly, You could have ten kids -- Host: But if he had a 1000 kids, 250 will get it. Lakshmi Mehta: One would expect. Host: 250 out of a 1000. Lakshmi Mehta: Yeah, but we have seen families they have had very bad luck and every single pregnancy has been affected and we have seen people who never knew they were carriers and got away with it and never had a child with the problem.