Understanding Autosomal Recessive Inheritance
* Recessive: A recessive gene only expresses its trait if two copies of the gene are present.
* Autosomal: The gene is located on a non-sex chromosome (autosome).
Scenario:
* Both parents are carriers. This means each parent has one normal gene (let's call it "N") and one defective gene (let's call it "s"). Their genotypes are "Ns".
Possible Genotypes for the Child:
When the parents have children, each parent contributes one gene to their offspring. Here are the possible combinations:
* NN: Normal, not a carrier
* Ns: Carrier, no sickle-cell disease
* sN: Carrier, no sickle-cell disease (same as Ns)
* ss: Has sickle-cell anemia
Probability of Being a Carrier:
* Out of the four possible genotypes, two of them (Ns and sN) represent a carrier.
* Therefore, the likelihood of the child being a carrier is 2 out of 4, or 50%.
Important Note: While this explanation gives the basic probability, it's important to remember that:
* Genetic counseling: People with a family history of sickle-cell anemia should consider genetic counseling to get personalized information about their risk.
* Testing: There are tests that can determine if a person is a carrier or has sickle-cell anemia.
