Karen and Steve each have a sibling with sickle-cell disease. Neither Karen nor
ID: 178883 • Letter: K
Question
Karen and Steve each have a sibling with sickle-cell disease. Neither Karen nor Steve nor any of their parents have the disease, and none of them have been tested to see if they have the sickle-cell trait. Based on this incomplete information calculate the probability that if this couple has a child, the child have sickle-cell disease. In 1981, a stray black cat with unusual rounded, curled-back ears was adopted by a family in California. Hundreds of descendants of the cat have since been born, and cat fanciers hope to develop the curl cat into a show breed. Suppose you owned the first curl cat and wanted to develop a true-breeding variety. How would you determine whether the curl allele is dominant or recessive? How would you obtain true-breeding curl cats? How could you be sure they are true-breeding?Explanation / Answer
9. Sickle cell cell anemia is an autosomal recessive disorder where the person affected with the disease have sickle celled RBC's instead of normal cells . this is due to a mutation in the haemoglobin molecule.Persons affected with the disease have anemia,repeated infections and periodic episodes of pain.This is due to the rapid break down of the RBC's in the affected person.
As mentioned since the disease is autosomal it is not sex linked inheritance as the genes responsible for the disease are seen on autosomes .The genes are located on chromosome 11. The mutated copy of the gene is beta haemoglobin instead of the normal haemoglobin A.
The disease is also recessive which means if the disease has to be expressed both the copies should be present.In the question as both the parents have siblings affected with the disease the chances of them being as carriers with a copy of mutant gene is high and further the inheritance pattern will follow typical Mendelian 1:2:1 ratio where one of the child will be affected by the disease two will be carriers and one un affected.
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