- Information
- AI Chat
The Hardy-Weinberg Equation Worksheet - AP
Pensacola State College
Preview text
The Equation How can we make predictions about the characteristics of a population? Why? Punnett squares provide an easy way to predict the possible genotypes for an offspring, but it is not practical 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 HardyWeinberg 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 Males Females Bb bb Bb bb bb Bb bb Bb Bb bb Bb bb bb Bb bb Bb Bb bb Bb bb bb Bb bb Bb 1. How many mating pairs are illustrated in Model 1? 12 2. Describe the parents in each mating pair in Model 1. Use terms such as homozygous, heterozygous, dominant, and recessive. One parent is heterozygous and the other is homozygous recessive. 3. Use two Punnett squares to determine the possible genotypes for offspring from the pairs. The Equation 1 4. If each mating pair has one offspring, predict how many of the first generation offspring will have the following genotypes. BB 0 Bb 6 bb 6 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? This pairing scenario is too organized. It is not very likely. b. Why is Model 1 labeled Each heterozygous beetle was mated with a homozygous beetle purposefully. 6. List two other pairings that might occur in the population in Model 1 if the beetles were allowed to mate naturally. Bb with bb bb with bb 7. If the population of beetles in Model 1 mated naturally would your prediction for the offspring in Question 4 still be valid? Explain. No, the prediction from the Punnett squares would not include the offspring from the other two types of pairings. 8. Discuss in your group the limitations of Punnett square predictions when it comes to large populations. Summarize the key points of your discussion here. Punnett squares only give the predicted offspring ratios for one type of pairing. In large populations it would be cumbersome to do a Punnett square for every possible pairing scenario. There is no way to know how many of each type of pairing will occur naturally in a large population. 2 Activities for Biology Read This! When it comes to mating in natural populations with hundreds or even millions of individuals, it is difficult, 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? Each organism has 2 alleles. 2 24 48 alleles. 13. What is the probability of an offspring from the Model 2 population getting a dominant allele? 0 14. What is the probability of an offspring from the Model 2 population getting a recessive allele? 0 15. If p is used to represent the frequency of the dominant allele and q is used to represent the frequency 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. forget there are two ways to get a heterozygous or bB.) BB 0 0 0 Bb 0 0 0 0 0 0 0 bb 0 0 0 17. Check your answers in Question 16 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. Since there are only three possible outcomes for the genotype of an offspring, the sum of those possible outcomes would represent or 1. 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 p x p Bb pq pq 2pq bb q x q 19. Complete the equation: p2 2pq q2 2pq 1 4 Activities for Biology Read This! The equations you have just developed, p q 1 and p2 2pq 1, were first developed G. H. Hardy and Wilhelm Weinberg. They represent the distribution of alleles in a population when The population is large. Mating is random. All genotypes are equally likely to reproduce (there is no natural selection). No organisms enter or leave the population (there is no immigration or emigration). No mutations occur. In other words, the group of alleles available in the population must be very stable from generation to generation. If the distribution of genotypes in a population matches that predicted the HardyWeinberg equation, then the population is said to be in equilibrium. If the distribution of genotypes in a population does not match that predicted the equation, then the population is said to be evolving. 20. Consider the requirements for a population to be in equilibrium. In the natural world, are populations likely to be in equilibrium? Justify your reasoning. It is very unlikely that all of the criteria in the Read This! box would be met in a population, so finding a population in equilibrium would be nearly impossible. 21. anemia is a genetic disease. The allele is recessive, but individuals with the homozygous recessive genotype (ss) often die prematurely due to the disease. This affects approximately of the population in Africa. Use the equations to calculate the following: a. The frequency of the recessive allele in the population (q). .30 b. The frequency of the dominant allele in the population (p). 1 0 p p 0 c. The frequency of homozygous dominant individuals in the African population. 0 x 0 0 d. The frequency of heterozygous individuals in the African population. 0 x 0 0 e. Based on this analysis, is the African population in equilibrium? Justify your answer. No. Because the members of the population that contract sickle cell because they are homozygous recessive will likely die before reproducing, the frequency of alleles in the population is not stable. There is natural selection taking place. The Equation 5 Extension Questions 25. The ability to taste PTC is due to a single dominant allele You sampled 215 individuals and determined that 150 could detect the bitter taste of PTC and 65 could not. Calculate the following frequencies. a. The frequency of the recessive allele. q 0 b. The frequency of the dominant allele. p 0 c. The frequency of the heterozygous individuals. x 0 26. Sixty flowering plants are planted in a flowerbed. Forty of the plants are homozygous dominant. Twenty of the plants are homozygous recessive. The plants naturally pollinate and reseed themselves for several years. In a subsequent year, 178 plants, 190 plants, and 52 plants are found in the flowerbed. Use a analysis to determine if the population is in equilibrium. P 0 which is not significant, because flowering population appears to be in Hardy equilibriums. The Equation 7
The Hardy-Weinberg Equation Worksheet - AP
University: Pensacola State College
