John Hay
John Hay Biomedical
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Here's an example of what's due today

SNP and PTC case

Thu, Oct 22, 2026 · Week 9 · Genetics of Disease (Medical Interventions)

Today's goal: Connect a single-nucleotide polymorphism to a phenotype using the PTC-tasting genotype dataset.

Learn first

What a finished product looks like

This is a model of the work you should turn in today. Use it to check your own: match the structure and the level of detail, do not copy it. Your data and wording should be your own.

Genotype-to-phenotype table
Completes: Completes the SNP case analysis: a genotype-to-phenotype table for three individuals with homozygous or heterozygous labels, an evidence sentence, and a carrier prediction.

I found the SNP column for the TAS2R38 PTC-tasting gene and matched each person's genotype to their tasting phenotype. I used T for the taster allele and t for the non-taster allele.

Does the tasting allele track with the trait? Yes. Everyone with at least one T allele tasted PTC, and the only non-taster was homozygous tt. Evidence: Person 1 (TT) and Person 2 (Tt) both tasted; Person 3 (tt) did not, so the T allele tracks with tasting and behaves as dominant.

Carrier prediction: Person 2 is a heterozygous taster (Tt). They show the taster phenotype but carry one non-taster allele, so they could pass the non-taster allele to a child.

PersonGenotypeZygosityPhenotype
1TThomozygoustaster
2Ttheterozygoustaster
3tthomozygousnon-taster
Genotype-to-phenotype table: TT and Tt individuals taste PTC; the tt individual does not, showing the taster allele is dominant.

Also due today: Submit your genotype-to-phenotype table and prediction to the course shell.

Check yourself

WebXam problem for today's skill

One exam-style question that uses exactly what you practiced today. Try it before you reveal the answer, then read why each choice is right or wrong.

WebXam-style domain: Biotechnology Research and ExperimentsSelf-check skill: Linking a SNP genotype to phenotype and identifying carriers
For the PTC-tasting gene, the taster allele (T) is dominant over the non-taster allele (t). A person who can taste PTC but could still pass a non-taster allele to a child must have which genotype?

Tap an answer to see the full explanation. Nothing is recorded or graded.

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