BIOLOGY 152 Lecture Notes - Lecture 5: Allele Frequency, Directional Selection

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9 Feb 2017

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If nothing is happening to alleles to cause them to leave population, then allele frequencies will remain the same from generation to generation. Test and if observed frequency matches expected frequency then there is no evolution good test if you want to know when evolution is occurring. If question tells you population is in equilibrium: just plug numbers into the equation this has very little use scientifically remember the equation is p^2+2pq+q^2. If question asks if it meets the conditions for hardy weinberg equilibrium. Calculate allele frequency from observed genotype frequency. Use this to determine your expected value. If they match then you have hardy weinberg equilibrium, if not evolution is occurring. If knocked out of equilibrium for some reason, a population will require one generation of random mating and no evolutionary mechanisms acting on alleles to get back. Can have new genotype frequency that conforms to the equilibrium. Although the frequency is different that doesn"t mean it doesn"t conform.

Related Questions

29. You test if this population of plants is in Hardy-Weinberg equilibrium at the flower colour locus. You conduct a chi-square test to compare the observed and expected frequencies of the two alleles. Your calculated chi-square value is 4.26. If the critical chi-square value is 3.84, which statement is FALSE? a. There is a significant difference between the observed and expected allele frequencies at this locus in the population. b. There has been a significant change in the allele frequencies at this locus from generation to generation. c. The population is in Hardy-Weinberg equilibrium at this locus.. d. Some evolutionary force is at work at this locus.

Question:

Question 1: What is NOT a force of evolution?

Mutation of genes

Genetic drift

Equilibrium of populations

Migration of populations

Question 2:

Crossing true breeding dark-coated sheep with true breedinglight-coated sheep always results in 100% dark-coated offspring.You are screening a population of 300 Soay sheep for coat color,and you count 243 dark sheep and 57 light sheep. What is thegenotype frequency of the homozygous recessive sheep forTYRP1 gene if the population is in Hardy-Weinbergequilibrium?

.421

0..176

0.864

0.190

Question 3:

In the same population, if it is under Hardy-Weinbergequilibrium, how many individuals do you expect to be heterozygousat TYRP1?

217

0.492

148

124

Question 4:

Rabbit's ears can be either short (dominant) or floppy(recessive). If a population of rabbits in Hardy-Weinbergequilibrium has 250 short eared rabbits and 100 floppy earedrabbits, what is the allele frequency of the "short" allele?

.465

0.714

0.845

0.535

Question 5:

To calculate degrees of freedom, we use the following formula:Degrees of freedom - the number of constraints imposed on yourcomparison. How many constraints are there when we use theChi-square test for Hardy Weinberg equilibrium?

Question 6:

You perform a Chi-square test for gene X and find thep-value to be greater than 0.05. What can you say with 95%certainty about this population?

This population is in Hardy-Weinberg equilibrium at theX locus: gene X isinfluenced by at least oneforce of evolution.

This population is in Hardy-Weinberg equilibrium at theX locus: gene X is notinfluenced by any forces ofevolution.

This population is not in Hardy-Weinberg equilibrium at theX locus: gene X isinfluenced by at least oneforce of evolution.

This population is not in Hardy-Weinberg equilibrium at theX locus: gene X is notinfluenced by any forces ofevolution.

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1 A) Cystic Fibrosis is an autosomal recessive disease, 1 out of every 2500 individuals of Caucasian descent in the US have cystic fibrosis. What frequency of cystic fibrosis carriers would you expect in the Caucasian population of the US under Hardy Weinberg Equilibrium? Show your work. (1 pt)

1 B) You know that penguin tuxedo color is a classic Mendelian single-gene trait, the allele for black and white tux coloring (T) is dominant over gray and white tux coloring (t). In a population of penguins, there are 400 black and white tuxedoed penguins and 200 gray and white tuxedoed penguins.

(i) Which observed genotypic or allelic frequencies can be calculated from this scenario without assuming Hardy Weinberg Equilibrium? (1.5 pt)

(ii) In one to two sentences, explain why differences may arise between observed and expected genotype frequencies. (1 pt)

1 C) You are studying inheritance of external keratin features in a dinosaur. Analysis has found that the presence of feathers is due to codominance between the AS (scales) and AH (horns) alleles. In one generation of a population you find 78 scaled dinosaurs, 76 feathered dinosaurs, and 64 horned dinosaurs.

(i) What are the observed allele frequencies of AS and AH ? Use p for the frequency of AS and q for the frequency of AH . Show your work. (1.5 pt)

(ii) What are the observed genotypic frequencies? Show your work. (1 pt)

(iii) Given the allelic frequencies calculated above, what are the expected number of scaled, feathered, and horned dinosaurs in a population of the same size (218) under Hardy Weinberg Equilibrium? Show your work. (1.5 pt)

(iv) Use a chi-square test to examine whether the gene you are studying is under Hardy Weinberg Equilibrium in this population. Show your work. Do you accept or reject the null hypothesis? (2 pts)

BIOLOGY 152 Lecture Notes - Lecture 5: Allele Frequency, Directional Selection

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