The probability that their child will have sickle-cell disease is 1/4.
Why is this correct?
Karen and Steve both have a sibling affected by sickle-cell disease. Despite neither Karen nor Steve, nor their parents, showing signs of the disease, none of them have undergone testing to confirm if they carry the sickle-cell trait.
Given this limited information, let's ascertain the probability that their child might inherit sickle-cell disease. This hereditary condition follows a recessive pattern, manifesting only if both parents carry the sickle-cell trait.
In light of their siblings' condition, it's deduced that each of their parents likely carries the sickle-cell trait. Assessing whether Karen and Steve carry the trait provides insight into the likelihood of their child inheriting the disease.
Employing a Punnett square to outline genetic possibilities:
S = Sickle-cell allele
N = Normal allele
Karen's Possible Gametes: S or N
Steve's Possible Gametes: S or N
Potential genetic combinations:
| S | N |
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S | SS | SN |
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N | SN | NN |
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For their child to develop sickle-cell disease (SS), both Karen and Steve must carry the sickle-cell trait (SN) and pass on the sickle-cell allele (S). This particular outcome arises in 1 out of 4 possibilities (SN).
Consequently, the probability that their child will have sickle-cell disease is 1/4.
Complete 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 will have sickle-cell disease. Express your answer as a fraction using the slash symbol and no spaces (for example, 1/16).