AP Biology Blog (:: Hardy-Weinberg Lab

Hardy-Weinberg Equilibrium Model Planner

This document exists to help you plan your approach as you work on your Hardy-Weinberg Model. Some time spent thinking about what you are going to do, and how you are going to do it, can go a long way toward helping you create the best model you can.

1. Pick a question to investigate. Remember that the idea of your model is to help illustrate how some source of evolutionary pressure can affect the distribution of alleles in a population. There is really no limit to what you could decide to look at. Certainly, it’s very possible to model any of the major evolutionary pressures (natural selection, genetic drift, gene flow, sexual selection) in the spreadsheet model. But don’t feel limited. Also, don’t feel overwhelmed. There is nothing wrong with simple. Use the space below to write down some ideas about the question(s) you are interested in investigating. If you do have multiple questions, you’ll need to make a choice before moving into #2 (or maybe you’ll revise your choice if the rest of this isn’t working out like you hoped it would).

Why is polydactyly a dominant trait, but is not a common trait amongst most human populations?

2. Determine the ingredients. What are you going to need to do to your model to help you analyze your question? You’ve already got a good foundation in the model that we created in class. It would be silly to start from scratch. But you are going to need to figure out what you are going to have to do to change/expand your model for your purpose. Sketch some ideas in the space below. Keep them general.

-We would use “A” as dominant alleles and “B” as recessive alleles.

-I will make the assumption that all the organisms in our hypothetical populations are diploid.

-Gametes for the next few generations would be would be random.

-I need to determine how the allele frequencies might change from generation to generation.

-Many people mistaken “dominant” for common. The presence of polydactyl can be caused by a dominant mutation, however, it only occurs in .31-6.18 births of 1000, which may vary depending on ethnicity. That means although mutation is dominant, it is very unlikely to have that gene mutation.

3. Quantify your ideas. You are going to have to translate the ideas that you have into the language of the spreadsheet. Maybe you need to alter equations or add additional ones. This step is quite possibly the most difficult one. Don’t get discouraged. Spend some time and think about what you are doing before you start making changes to your foundational model. Remember to simplify things as much as possible. It may even be helpful for you to sketch out your spreadsheet model here.

-The determination of a person obtaining polydactyly is based according to family history. Polydactyl tends to be a strong family trait that usually does not skip generations and for that reason, the chance of passing on this traits is 50%, this only being if the parent has polydactyly. Discrepancies between percentages would have to be due to the fact if perhaps a parent has polydactyly but as a recessive trait, therefore lowering possibilities. This can occur even when your family has no family history of polydactyl, again chances are highly varied.

Lets consider the scenario that a father has heterozygous dominant for the trait of polydactyly (Rr) and the mother is is heterozygous as well but not for the trait (Rr). The probability of the child having polydactyly would be 25%.

4. Implement your changes. Now is the time to actually make the changes to your model. Here are a few points to keep in mind:

Feel free to run off a “copy” of your foundational model, and make your changes to that instead. Just select the sheet tab at the bottom of the spreadsheet, and use the duplicate option. You can also rename sheets, and do all sorts of other things from that menu.
Remember that color and borders are your friends. They help keep you organized.