The Hardy-Weinberg Equation How can we make predictions about the characteristics of a population? Herricks High School - SCIENCE 10080

Why? The Hardy-Weinberg Equation How can we make predictions about the characteristics of a population? Punnett squares provide an easy way to predict the possible genotypes for an offspring, but it is not practi- cal to perform a Punnett square analysis on all possible combinations of all members of a population to predict what the population might look like in the future. For that we must turn to statistics. The Hardy- Weinberg equation is a tool biologists use to make predictions about a population and to show whether or not evolution is occurring in that population. Model 1 – Controlled (Selective) Mating Males Females 1. How many mating pairs are illustrated in Model 1? 2. Describe the parents in each mating pair in Model 1. Use terms such as homozygous, heterozy- gous, dominant, and recessive. 3. Use two Punnett squares to determine the possible genotypes for offspring from the pairs. 4. If each mating pair has one offspring, predict how many of the first generation offspring will have the following genotypes. 5. Imagine the 24 beetles in Model 1 as a population in an aquarium tank. a. How likely is the pairing scenario in Model 1 to take place during the natural course of things within that tank? b. Why is Model 1 labeled “Selective Mating”? 6. List two other pairings that might occur in the population in Model 1 if the beetles were allowed to mate naturally. 7. If the population of beetles in Model 1 mated naturally would your prediction for the offspring in Question 4 still be valid? Explain. 8. Discuss in your group the limitations of Punnett square predictions when it comes to large popu- lations. Summarize the key points of your discussion here. ™ This study source was downloaded by from CourseH on :37:12 GMT -05:00 Model 2 – Population Genetics 9. ompare the organisms in the population in Model 1 with the organisms in the population in Model 2. 10. Individually match up twelve mating pairs from the population in Model 2 that might occur in a natural, random mating situation. 11. Compare your set of mating pairs with other members of your group. Did your mating scheme match anyone else’s in the group? This studTy shouercHe waarsddyo-wWnloeaidnedbbeyrg10E00q00u8a1t9i9o46n675 from CourseH on :37:12 GMT -05:00 3 Read This! When it comes to mating in natural populations with hundreds or even millions of individuals, it is dif- ficult, maybe even impossible, to think of all the mating scenarios. After several generations of leaving things up to nature, the alleles that are present in the population will become more and more randomized. Statistics can help biologists predict the outcome of the population when this randomization has occurred. If the population is particularly nonrandom to start, this randomization may take several generations. 12. How many total alleles are in the population in Model 2? 13. What is the probability of an offspring from the Model 2 population getting a dominant allele? 14. What is the probability of an offspring from the Model 2 population getting a recessive allele? 15. If p is used to represent the frequency of the dominant allele and q is used to represent the fre- quency of the recessive allele, then what will p + q equal? 16. Use your knowledge of statistics to calculate the probability of an offspring from the Model 2 population having each of these genotypes. Support your answers with mathematical equations. 17. Check your answers in Question 16 by adding the three values together. Your sum should be equal to one. Explain why the sum of the three answers in Question 16 should be equal to one. 18. Using p and q as variables, write formulas for calculating the probability of an offspring from a population having each of the following genotypes. BB Bb bb 19. Complete the equation: ™ This study source was downloaded by from CourseH on :37:12 GMT -05:00 a. How might this trait affect the values calculated in Question 21 and the population’s tendency toward Hardy-Weinberg equilibrium? 23. Consider the beetle population in Model 2. Imagine a change occurred in the beetle’s ecosystem that made it easier for predators to spot the white beetles and six of the white beetles were lost. Predict the genotype frequency in the population after this event. 24. Compare your answers to Question 22 with those of Question 16. How do your answers support the conclusion that the population is not in Hardy-Weinberg equilibrium? ………………………………………………CONTINUED……………………………… 7