Biology: The Dynamic Science (MindTap Course List)
4th Edition
ISBN: 9781305389892
Author: Peter J. Russell, Paul E. Hertz, Beverly McMillan
Publisher: Cengage Learning
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Chapter 21, Problem 15TYK
Summary Introduction
To review:
Designing of an exercise by taking two varieties of beans to represent the two alleles at the same gene locus, to illustrate the affects of
Introduction:
Genetic drift is also known as allelic drift or Sewall Wright effect. This is a mechanism of evolution accompained with the change in the frequency of an existing gene variant or allele in a population due to chance (Sampling error). The process of genetic drift takes place in all populations of non-infinite size, but the observed effects are strongest in small populations. Bottleneck effect (sharp reduction of population size by a natural disaster) and founder effect (dissociation of small group from the main population) shows the major effect on genetic drift.
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Consider the B locus which has two alleles in a population: B and b. Researchers examined the genotypes several individuals for this locus and obtained the following numbers
B/B: 302individuals
B/b: 56individuals
b/b: 17individuals
If the B locus is at Hardy-Weinberg equilibrium, what would the expected number of individuals with the Bb genotype? Round your answer to the closest full number.
A mountain region has a population of 5,000 mountain goats. You score these animals for the R locus and find that this locus has two alleles, R (dominant) and r (recessive). 3200 individuals are homozygous dominant, 1,600 are heterozygous, and 200 are homozygous recessive.
a) Calculate the allele frequencies for this population. Show your work.
b) Calculate the observed genotypic frequencies for this population. Show your work.
c) Calculate the expected genotype frequencies if the population is in Hardy-Weinberg equilibrium. Show your work.
d) Does this population appear to be at H-W equilibrium? Why or why not? (You do not need to analyze this statistically).
Answer the question, using the graphs attached.
Chapter 21 Solutions
Biology: The Dynamic Science (MindTap Course List)
Ch. 21.1 - If a population of skunks includes some...Ch. 21.1 - Prob. 2SBCh. 21.1 - What factors contribute to phenotypic variation in...Ch. 21.2 - Prob. 1SBCh. 21.2 - Why is the Hardy-Weinberg principle considered a...Ch. 21.2 - Prob. 3SBCh. 21.3 - Which agents of microevolution tend to increase...Ch. 21.3 - Which mode of natural selection increases the...Ch. 21.3 - In what way is sexual selection like directional...Ch. 21.4 - How does the diploid condition protect harmful...
Ch. 21.4 - Prob. 2SBCh. 21.4 - Prob. 3SBCh. 21.5 - How can a biologist test whether a trait is...Ch. 21.5 - Why are most organisms adapted to the environments...Ch. 21 - The reason spontaneous mutations do not have an...Ch. 21 - The phenomenon in which chance events cause...Ch. 21 - Prob. 3TYKCh. 21 - Prob. 4TYKCh. 21 - Prob. 5TYKCh. 21 - Which of the following represents an example of...Ch. 21 - A population of mice is at HardyWeinberg...Ch. 21 - If the genotype frequencies in a population are...Ch. 21 - An Eastern European immigrant carrying the allele...Ch. 21 - If a storm kills many small sparrows in a...Ch. 21 - Prob. 11TYKCh. 21 - Discuss Concepts Many human diseases are caused by...Ch. 21 - Prob. 13TYKCh. 21 - Apply Evolutionary Thinking Captive breeding...Ch. 21 - Prob. 15TYKCh. 21 - Design an experiment to test the hypothesis that...Ch. 21 - Peter and Rosemary Grant of Princeton University...
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- In this version of the simulation (500 population size; 500 carrying capacity), all fish are equally likely (though not 100% likely) to survive and reproduce. There are no mutations, nor are there any entering or leaving the population. When they reproduce, they choose a mate from the pool at random and produce ten offspring by chance with the probability of the offspring’s genotypes determined by the punnett square. What caused the allele frequencies to change and vary in the trials? (ex attached).arrow_forwardPlease refer to the Chi squared step by step document for an example to follow. 4a. A large random sample taken from a natural population of flowering plants found 300 plants with red flowers (RR genotype), 150 with pink flowers (Rr genotype) and 38 white flowers (rr genotype). Is the population in HWE? Step 1 Calculate the frequencies of alleles R and r. Include the formula for calculating allele frequencies in a population. Ans: Step 2 Based on the allele frequencies how many individuals are expected to a certain genotype? Calculate by multiplying the number of individuals in population (n) x frequencies of alleles for that genotype: Ans: T Step 3 Fill in the Table Below Genotype Ans: RR Rr rr Observed Expected Obs - Exp Step 3 Use the following formula to calculate the Chi squared value., Note calculate for each genotype and get the sum. (Obs - Exp)² Exp ³x²³ = [ (O - E)² E Step 4 Determine the Chi Square value for 1 Degree of Freedom and for the probability 0.05 from the table…arrow_forwardExample: I go to a different population of fruit flies that have the same two alleles for eye-color. I suspect that the alleles occur in different frequencies in this second population. I sample 1000 flies and discover 10 that have brown eyes. What are the estimated frequencies of the "R" and "r" alleles in this population? Answer: Again, p2 + 2pq + q2 = 1. The term q2 = the relative frequency of homozygous recessive individuals, which corresponds to the ten brown-eyed flies I counted out of 1000 flies sampled. Thus, q2 = 10/1000 = 1/100. q = the square root of 1/100 or 0.1. Thus the frequency of "r" in this second population is 0.1 and the frequency of the "R" allele is 1 - q or 0.9. Problem 1: Phenylketonuria (PKU) is a disease caused by the build-up of the byproducts of metabolizing phenylalanine. It is caused by a defective, recessive allele. If a child is homozygous for this recessive allele, it will develop PKU. In the United States, PKU is detected in approximately 1 in 10,000…arrow_forward
- Suppose that a population is at equilibrium between mutation and selection for a deleterious recessive allele, where s = 0.5 and μ = 10−5. What is the equilibrium frequency of the allele? What is the selection cost?arrow_forwardCalculate selection for the following scenario. In a population of prairie dogs living on a prairie, prairie dogs with genotype AA have 9 offspring per year on average, those with genotype Aa have 5 offspring per year on average, and those with genotype aa have 8 offspring on average. Round selection to the nearest hundredth, report selection as a value ranging from "0.00" to "1.00" • Selection on genotype Aa: • Selection on genotype AA: • Selection on genotype aa: Which genotype has the highest fitness? Fill in the blank with homozygous dominant, heterozygous, or homozygous recessivearrow_forwardCalculate selection for the following scenario. In a population of prairie dogs living on a prairie, prairie dogs with genotype aa have 8 offspring per year on average, those with genotype Aa have 4 offspring per year on average, and those with genotype AA have 3 offspring per year on average. Round selection to the nearest hundredth, report selection as a value ranging from "0.00" to "1.00" Selection on genotype Aa: Selection on genotype AA: Selection on genotype aa: Which genotype has the highest fitness? Fill in the blank with homozygous dominant, heterozygous, or homozygous recessivearrow_forward
- Please help and explainarrow_forwardThe allele frequencies of the parents in our simulation were p = 0.75 and q = 0.25. The heterozygote has a selective advantage and therefore a fitness of W12 = 1. Assume the homozygotes have a fitness of W11 = 0.4 and W22 = 0.1, respectively. Calculate the allele frequencies after two rounds of selection and show your work.arrow_forwardexplain why “editing” is a metaphor for how naturalselection acts on a population’s heritable variationarrow_forward
- A researcher examines a locus, or marker, in which there is a particular C/T polymorphism in a population of interest. Let’s call this Locus 1. They obtain the following genotype counts in a sample of the population: CC:42, CT:16, TT:32. a) Calculate the genotype frequencies and the allele frequencies for Locus 1 in the sample.b) Calculate the observed heterozygosity (the frequency of heterozygotes) and the observed homozygosity (the total frequency of all homozygotes) in the sample. Ensure that these two frequencies add up to 1.arrow_forwardWhat is the frequency of cats in the current population that are homozygous dominant? Question 2 options: 0.52 0.68 0.84 0.89arrow_forwardThe plots show changes in the frequency of allele A1 during population genetic simulations (allele frequency through time plots). The sets of runs in the two panels differed in only one variable. What was the difference? 100% 80% 60% 40% 20% 0% 0 1000 2000 3000 4000 O The A1 mutation rate was less on the right O Balancing selection slowed the increase in A1 frequency on the right O Selection is weaker in the right panel O Selection is stronger in the right panel 5000 6000 7000 100% 80% 60% 40% 20% 0% 0 1000 2000 3000 4000 5000 6000 7000arrow_forward
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