ShmoopTube

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Here's your shmoop du jour, brought to you by sickle cells.

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If they're that sickle, they really should be at home in bed.

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If one parent is heterozygous for the sickle cell trait while the other parent does not

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carry it, what is the likelihood that their child will be a carrier?

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And here are the potential answers...

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All right, this is a pretty straightforward question... if we know what heterozygous means.

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If we don't... we can always eeny-meeny-miney-moe the answer...

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Let's assign S to represent a normal phenotype and s to represent a sickle cell phenotype:

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In genetics, heterozygous means you have one of the dominant S, and also an abnormal, recessive

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lowercase s.

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This means that one parent has the genotype of big S, big S, and one has the genotype

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big S, small S.

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If we write out a Punnett Square to represent the possible genetic combinations for the child...

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...we'll see that there is a 50% chance of the child being a carrier.

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So...our answer's C!

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Don't worry -- just because both your parents have a big S doesn't mean that you're going to have a... big S.

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No Punnett Square intended.

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