PTC Taster
  • Dominance describes the molecular relationship between products of two different alleles.
MINT Learning Objectives
  • Calculate allele frequency from genotype or phenotype numbers

  • Define allele in terms of DNA sequence

  • Define dominance in terms of alleles, DNA variants and protein variants

National Standards Alignments:
  • Vision and Change Core Concepts and Competencies (http://visionandchange.org)

    • Core Concept:

      • Structure and Function: Basic units of structure define the function of all living things.

      • Information Flow, Exchange, and Storage: The growth and behavior of organisms are activated through the expression of genetic information in context

    • Core Competencies:

      • Ability to use quantitative reasoning: Biology relies on applications of quantitative analysis and mathematical reasoning.

      • Ability to communicate and collaborate: Biology is a collaborative scientific discipline.

  • Biocore Guide (Brownell et al., https://doi.org/10.1187/cbe.13-12-0233)

  • Evolution: Mutations that change protein structure and/or regulation can impact anatomy and physiological function at all levels of organization.

  • Information Flow: Gene expression and protein activity are regulated by intracellular and extracellular signaling molecules. Signal transduction pathways are crucial in relaying these signals.

  • Information Flow: Organisms have sophisticated mechanisms for sensing changes in the internal or external environment. They use chemical, electrical, or other forms of signaling to coordinate responses at the cellular, tissue, organ, and/or system level.

  • Information Flow: Information stored in DNA is expressed as RNA and proteins. These gene products impact anatomical structures and physiological function.

  • Structure Function: The three dimensional structure of a molecule and its subcellular localization impact its function, including the ability to catalyze reactions or interact with other molecules. Function can be regulated through reversible alterations of structure e.g. phosphorylation.

  • Structure Function: Natural selection has favored structures whose shape and composition contribute to their ecological function.


  • Process of Science Skills, Pelaez, N, et al. “The Basic Competencies of Biological Experimentation: Concept-Skill Statements“ (2017). PIBERG Instructional Innovation Materials. Paper 4. http://docs.lib.purdue.edu/pibergiim/4

    • Observations

      •  Apply systematic observations to discern variable properties of components of biological systems

      • Compare observations to existing knowledge, models, or theories

    • Hypothesis

      • Use a model (i.e. an abstraction or simplification: an equation, computer simulation, conceptual drawing, or other explanatory representation that shows key elements and their relationships) to generate new hypotheses.

      • Generate multiple explanations of the natural world that are testable and potentially falsifiable

    • Measurement

      • Choose appropriate measurements based on available equipment, population/species, natural variation, and research question(s)

    • Sampling

      • Identify a target population(s) (might be molecules, cells, organisms, or populations) for the planned experiment

    • Measurement

      • Record data in an organized and systematic way using appropriate tables, forms, etc.

    • Inferences and conclusions

      • Determine and articulate whether data support or refute hypotheses and predictions

      • Align conclusion with analyses, hypotheses, research question(s), and existing knowledge

    • Representations

      • Distill results into clear numeric and/or graphical forms that are aligned with the experimental objective/question/hypothesis

Interactive Video Vignette Information
IVV Title: A Matter of Taste
IVV URL for Students:  
  • Copy the URL to the Clipboard. Either paste it into an email to your students, or use it to create a link in your course management system.
IVV Description
Two students studying genetics struggle to define dominance. They explore an example, PTC taster vs. nontaster phenotypes, and collect data in a science fair setting. The molecular reasons for the dominance relationship between alleles is discussed, and the common assumptions that dominant alleles are better, stronger, or more common are debunked.
Novice Ideas and IVV Learning Goals
Novice Ideas
  • Dominant (in terms of genetics) means stronger and/or better; Recessive version is bad

  • Dominant (in terms of genetics) means more common; Recessive is rare

  • Dominance suppresses or overwhelms the recessive allele

  • Recessive means not expressed or not present

  • An allele is just a unit of inheritance (for example, B/b and no more).

  • “Gene” and “allele” are abstract concepts rather than physical entities

  • Two alleles are very different, code for different proteins

  • Genes code directly for traits/Proteins work in isolation

  • Phenotype frequency = allele frequency

Ideas addressed in the IVV
  • Genes are sequences of DNA that code for a product

  • Two alleles may differ by one or a few nucleotides

  • The versions of the protein that are present are a result of the particular alleles that are present in the genome.

  • The dominant allele is the one whose associated phenotype is observed when the two alleles are present together. And nothing else.

  • None of the following can be predicted based on dominance: frequency, fitness, quality, usefulness to the organism

  • Both alleles may be expressed in the same cell

  • A trait is a complex outcome based on which alleles (of multiple genes) are present and how they are expressed.

  • Allele frequency can be calculated using HWE

Recommended In-class Curricular Material
Please see the MINT FAQ page for general information on the use of MINTs and IVVs with your class. The following curricular materials are provided as examples of resources that may be used in class to further student learning towards IVV and MINT learning objectives.
Assessment Question Information
The research team has developed multiple select questions for assessing IVV effectiveness. Please contact the research team if you are interested in assessing IVV use in your course.
Download this MINT

Acknowledgement

This material is based in part upon work supported by National Science Foundation (NSF) grants 1432286 and 1432303. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

Ó2018, RIT. Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.