Hardy-Weinberg Model

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Hardy-Weinberg Model Additional Practice Problems

Sickle cell anemia is caused by the deleterious HS allele. The WT allele is the HB allele. In a population of 200,000 individuals, the observed frequency of HSHS is 0.0023, HBHB is 0.7560, and HSHB is 0.241. How many are the heterozygous individuals?

A. 24,100

B. 8,290

C. 36,500

D. 48,200

E. 829,200

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Human blood type is determined by three alleles IA, IB, and IO. The alleles IA and IB are co-dominant to each other, and both are dominant to IO. Within a large, randomly mating population (640,000 individuals), the frequencies for the blood type alleles are 0.3 for the IA allele, 0.6 for the IO allele, and 0.1 for the IB allele. Calculate the expected numbers of people in the population having blood type O.

A. O = 243,400 people

B. O = 324,000 people

C. O = 194,400 people

D. O = 230,400 people

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A new kind of orchid is produced that develops only purple or pink flowers. Assume that flower color is controlled by a single-gene locus and that the purple allele (C) is dominant to the pink allele (c). A random sample of 1320 orchids from a large cultivated field yields 1.167 purple flowers and 153 pink flowers. What is the frequency of the pink allele in this field population?

A. pink allele frequency = 0.847

B. pink allele frequency = 0.12

C. pink allele frequency = 0.34

D. pink allele frequency = 0.39

E. pink allele frequency = 0.153

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A new kind of geranium is produced that develops only red or yellow flowers. Assume that flower color is controlled by a single-gene locus and that the red allele (R) is dominant to the yellow allele (r). A random sample of 1000 geraniums from a large cultivated field yields 800 red flowers and 200 yellow flowers. What is the frequency of the red alleles in this field population?

A. red allele frequency = 0.847 

B. red allele frequency = 0.55

C. red allele frequency = 0.82

D. red allele frequency = 0.61

E. red allele frequency = 0.153

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Hemophilia is an X-linked recessive trait. In a population, you find a frequency of 1 hemophiliac in 200 males. Assuming that this population is in Hardy-Weinberg equilibrium and that the sex ratio is 1:1, what is the frequency of CARRIER females?

A. 0.000025

B. 0.0475

C. 0.00995

D. 0.095

E. 0.004975

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Which of the following genotype frequencies of AA, Aa, and aa, respectively, satisfy the Hardy-Weinberg principle (i.e. which are in quilibrium)

A. 0.64, 0.27, 0.09

B. 0.16, 0.48, 0.36

C. Both A and B

D. Neither E nor B

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Consider the following population for the shown trait below. What is the frequency of the IA allele in this population? Assume Hardy-Weinberg equilibrium.

A. 0.620

B. 0.359

C. 0.467

D. 0.533

E. 0.308

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Assume that a trait is caused by the homozygous state of a gene that is recessive and autosomal. Nine percent of the individuals in a given population express the phenotype caused by this gene. What percentage of the individuals would be heterozygous for the gene? Assume that the population is in Hardy-Weinberg equilibrium.

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In a population of cattle, the following color distribution was noted: 36 percent red (RR), 48 percent roan (Rr), and 16 percent white (rr). Is this population in a Hardy-Weinberg equilibrium? What will be the distribution of genotypes in the next generation if the Hardy-Weinberg assumptions are met?

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What is the number of dominant alleles in a population of 100 individuals with the following genotypes: 30 BB, 60Bb, 10bb?

A. 40

B. 60

C. 90

D. 120

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Suppose pea color is determined by 2 alleles: the Y allele is yellow and is dominant over the y allele which is green. If the Y allele is found at a 0.9 frequency in a population, what is the frequency of the y allele in that population?

A. 0.81

B. 0.2

C. 0.1

D. 0.19

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Ina certain type of wild flower, red is the dominant color and white is the recessive color. Phenotypic red flowers can be either homozygous dominant (WW)  of heterozygous (Ww) in genotype. Whereas, the phenotypic white flowers are always homozygous recessive (ww).

The phenotypic characteristics of a field of flowers were studied by a group ofresearchers, 64% of the flowers were phenotypically red.

What percent of the flowers are genotypically heterozygous (Ww)?

A. 36%

B. 48%

C. 64%

D. 24%

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In a population of blue jays that is at Hardy-Weinberg equilibrium for two alleles forcrest height, 16% of the population shows the recessive trait. What percent of the population show the dominant phenotype?

A. 96%

B. 84%

C. 60%

D. 48%

E. 36%

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In a population of 100 alligators at Hardy-Weinberg equilibrium on the Wakulla River, 49 are homozygous dominant for bad breath(BB; not that you would get that close to notice). The genotype frequency of alligators that are heterozygous for this trait in this population is _____.

A. 49

B 0.09

C. 0.51

D. 0.42

E. it cannot be determined

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In cats, the Xb allele causes orange coat color and the XB allele causes black coat color. The alleles are X-linked and codominant, so heterozygotes are calico. Assume that a population offeral cats is in Hardy-Weinberg equilibrium, 70% of male cats in the population are black and 9% of female cats are orange. The frequency of the XB allele is _____ and we expect _____ offemale cats to be calico.

A. 49%; 42%

B. 70%; 42%

C. 30%; 42%

D. 70%; 49%

E. 49%; 30%

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Assume that all possible blood genotypes are present in a particular population that is in Hardy-Weinberg equilibrium with respect to the ABO blood-type alleles. If the frequency of the "IA" allele is 0.3 and the frequency of the "i" allele if 0.3, what is the most common blood phenotype in this population?

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A population of 264 rabbits in a national park is in H/W equilibrium with respect to the gene that controlsfur color. The allele for tan fur is dominant to the allele for white fur. If 105 rabbits have tan fur tails, what percent of the population are homozygous dominant? 

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What is the frequency of the purple allele when in a population of 1000 pea plants that all have purple flowers?

A. 0.75 (or 75%)

B. There's not enough information to calculate

C. 0.1 (or 10%)

D. 0.5 (or 50%)

E. 1.0 (or 100%)

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What is the frequency of the white allele in a population of 1000 pea plants that all have white flowers?

A. 1.0 (or 100%)

B. 0.5 (or 50%)

C. There's not enough information to calculate

D. 0.25 (or 25%)

E. 0.1 (or 10%)


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What is the frequency of the white flowers when the frequency of the purple allele (P) is 0.6?

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Gray color in horses iscaused by a dominant gene, G, and other colors by its recessive allele, g. A survey of 10,000 Arabian foals showed 76% gray. Assume random mating for color among parents.

A. What are the estimated gene frequencies?

B. What percent of the gray foals are expected to be heterozygous?

C. What percent of the parent group are expected to be heterozygous?

D. What is the probability that a randomly chosen stallion is homozygous GG?

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Among Western European people, 64% of the population find phenylthiocarbamide (PTC) to taste bitter. The remainder cannot taste it. What is the frequency of the dominant allele T which confers the ability to taste PTC?

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Red color is recessive to black. A group of 450 calves that resulted from random mating has 18 red calves. 

A. What is estimated gene frequency of the red gene?

B. What percent of the black calves are heterozygous?

C. What percent of the parent herd is heterozygous?

D. If you randomly choose two bulls, what is the probability that both are BB?

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Human blood type is determined by three alleles, IA, IB, and IO. The alleles IA and IB are codominant to each other, and both are dominant to IO. Within a large, randomly mating population (540,000 individuals), the frequencies for the blood type alleles are 0.3 for the IA allele; 0.6 for the IO, and 0.1 for the IB allele.

a. Calculate the expected number of people in the population having each blood type A, B, AB, and O.

b. Determine the percentage of type B people that are heterozygous.

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A population consists of 200 individuals with genotype information summarized below:

A. What is the frequency of the A allele?

B. What is the frequency of the a allele?

C. Is population at Hardy-Weinberg equilibrium?

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Suppose you are investigating an autosomal recessive disease known as "studious toxicosis" which occurs at a rate in the American college student population of 1 in 16 individuals. Students who inherited two recessive alleles (tt) have the disease. If we assume Hardy-Weinberg equilibrium in a large population of college students, what is the percentage of heterozygous carriers of the studious toxicosis allele in the population?

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The genotypic frequencies of the MN blood groups in various populations are shown below. Given this information, determine if the genotypic frequencies are in general agreement with the Hardy-Weinberg law.

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Given the following genotypic frequencies of AA = 0.39, Aa = 0.56, and aa = 0.05, is this population in Hardy-Weinberg equilibrium? Explain why the data does or does not satisfy the Hardy-Weinberg equilibrium.

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Among Arabs, the frequencies of alleles determining the ABO blood type groups were estimated as IA = 0.209, IB = 0.129, IO = 0.660. What are the expected genotypic frequencies?

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M and N are blood groups separate from A, B, and O. It is controlled by two alleles of one gene, LM and LN. People with blood type M are homozygous for , people with type N blood are homozygous for , and people who have blood type MN are heterozygous. Three different human populations have the following MN blood group frequencies shown below.

a) What are the allele frequencies for M and N in each population?

b) Which populations are in Hardy-Weinberg equilibrium?

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Which of the following is an assumption of Hardy-Weinberg equilibrium?

A. Every individual in the population always mates with an individual with a different genotype.

B. Every individual in the population has an equal probability of surviving and reproducing.

C. Genotypes sometimes mutate into other genotypes.

D. The total number of individuals (population size) changes from generation to generation.

E. There is separation of soma and germline.

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Within a population of butterflies, the color brown (B) is dominant over the color white (b), and 40% of all the butterflies are white. Given this information, calculate the following:

A. The percentage of heterozygous butterflies in the population.

B. The frequency of homozygous dominant individuals.

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In house cats, the presence of black splotches is coded for by a dominant allele S; the recessive allele s codes for no black splotches. In a very large feral house cat population, you find that 5/9 of the cats have black splotches.

A. Assuming random mating, no natural selection on black splotches, and no mutation or gene flow, what proportion of the cats in the population are heterozygous at the S locus?

B. What will be the frequency of the dominant allele S in the following generation?

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Having a widow's peak hairline is a Mendelian trait that exhibits complete dominance. Imagine 51% of Americans have a widow's peak. If this population is in Hardy-Weinber equilibrium, what percentage of the population must be heterozygous for this trait?

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Hardy-Weinberg equilibrium is utilized to predict allele frequencies in populations from generation to generation. For this equilibrium to be achieved, there are certain requirements (disruptive and dispersive) that must be met. What are they? Failure to comply to these expectations may suggest that something biologically interesting is occurring. Give an example of what that something interesting could be.

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What 3 assumptions make an "deal population" that behaves according to the Hardy-Weinberg equilibrium?

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A population has 36% recessive homozygotes. What would the expected frequency of the homozygous dominant genotype be?

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Compare the observed genotype frequencies you just calculated with the genotype frequencies expected if the population is in Hardy-Weinberg equilibrium. At day 7, is the seedling population in Hardy-Weinberg equilibrium, or is evolution occurring?

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What happens in a population that is not in Hardy-Weinberg equilibrium? 

Drag the labels to the table below to describe how allele frequencies would be affected under different conditions. Remember that p is the frequency of the CR allele, and q is the frequency of the CW allele. Labels may be used once, more than once, or not at all.

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Using the day 7 data, what is the frequency of the CGallele (p)?

Using the day 7 data, what is the frequency of the CYallele (q)?

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In a given population, only the "A" and "B" alleles are present in the ABO system; there are no individuals with type "O" blood or with O alleles in this particular population. If 200 people have type A blood, 75 have type AB blood, and 25 have type B blood, what are the allelic frequencies (p and q) of this population? Assume type A blood= p and type B blood= q.


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There is a population with the following genotype frequencies: 3200 WW, 1600 Ww, and 200 ww. Is this distribution of genotype frequencies consistent with Hardy-Weinberg equilibrium? If so, why? Show your calculations.




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The fraggles are a population of mythical, mouse-like creatures that live in underground tunnels and chambers beneath a large vegetable garden (which supplies their food). Of the 80 fraggles in this population, 60 have green fur and 20 have gray fur. Green fur is controlled by a dominant allele and gray fur by a recessive allele. Assuming Hardy-Weinberg equilibrium, how many fraggles are homozygous dominant?

a. 0.25

b. 40

c. 60

d. 0.50

e. 20

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In a population of fiddler crabs, Uca pugilator, that is in Hardy-Weinberg equilibrium for two alleles, L and l (where L causes long antennae and l causes short antennae), 84% of the population show the dominant phenotype. What is the frequency of heterozygotes?

a. 0.8

b. 0.41

c. 0.48

d. 0.27

e. 0.04

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For a trait (bumpy or smooth skin) with two alleles (where smooth is the recessive allele), a population of 56 toads not in Hardy- Weinberg equilibrium has 12 heterozygotes, 32 homozygous dominant toads, and the remainder have smooth skin. What is the frequency of the dominant allele in this population?

a. 0.68

b. 0.57

c. 0.66

d. 0.34

e. 0.79

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What is the frequency of individuals with Type B blood in a human population in Hardy-Weinberg equilibrium in which all possible blood genotypes are present if the frequency of individuals with Type O blood is 0.09 and the frequency of the I A allele is 0.5?

a. 0.04

b. 0.12

c. 0.24

d. 0.16

e. it cannot be determined from the information given

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In a study of a population of blue-footed boobies that is in Hardy-Weinberg equilibrium, you find that 49% of the boobies have the recessive wing-color phenotype. Wing color is determined by a single autosomal gene for which there are two alleles. What would be the percentage of heterozygotes in the population?

a. 59%

b. 21%

c. 42%

d. 9%

e. it cannot be determined from the information given

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In peas, a gene shows incomplete dominance for flower color such that RR = purple, Rr = pink, and r = white. In an isolated pea patch, a killing frost takes the population out of H/W equilibrium and leaves only 36 plants with white flowers, 7 with pink flowers, and 14 with purple flowers. What is the frequency of the recessive allele in the surviving population population?

a. 0.31

b. 0.69

c. 0.63

d. 0.60

e. 0.37

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All of the following are criteria for maintaining Hardy-Weinberg equilibrium involving two alleles except ____.

a. there should be no natural selection.

b. matings must be random.

c. gene flow from other populations must be zero.

d. populations must be large.

e. the frequency of all genotypes must be equal.

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You have a population of 100 individuals in HW equilibrium and there are two alleles at the T locus (T and t). If there are 64 individuals in the population with genotype tt, what is the expected frequency of the t allele under HW?

a. 0.05  

b. 0.06   

c. 0.8   

d. 0.75   

e. 1.0

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A population of cats is in Hardy Weinberg equilibrium for the S locus which causes patches of white fur. There are two alleles S and s. The frequency of the S allele is 0.2 and the frequency of the s allele is 0.8. What is the expected frequency of Ss cats in the population?

a. 1.0     

b. 0.2     

c. 0.32

d. 0.16      

e. 0.8

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The most common allele for any trait is always the dominant allele. 

a. True    

b. False

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In the Hardy-Weinberg equation, p + 2pq + q 2 = 1. If the dominant allele frequency is 0.8, what percent of the population will be homozygous recessive? 

a.  0.64

b.  0.32

c.  0.04

d.  0.16

e.  0.40

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In the Hardy-Weinberg equation, p 2 + 2pq + q 2 = 1. If the dominant allele frequency is 0.8, what percent of the population will be homozygous dominant? 

a.  32%

b.  16%

c.  4%

d.  64%

e.  40%

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In the Hardy-Weinberg equation, p 2 + 2pq + q 2 = 1. If the dominant allele frequency is 0.8 what percent of the population will be heterozygous? 

a.  32%

b.  16%

c.  64%

d.  4%

e.  40%

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At Hardy-Weinberg equilibrium: 

a.  Allele frequencies change from one generation to the next

b.  Evolution does not occur

c.  Allele frequencies change from one generation to the next so evolution does not occur

d.  Allele frequencies remain constant from one generation to the next so evolution does not occur

e.  Allele frequencies remain constant from one generation to the next

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In the Hardy-Weinberg equation, p2 + 2pq + q2 = 1: 2pq represents: 

a.  The frequency of homozygous recessive individuals

b.  The frequency of homozygous dominant individuals

c.  The frequency of heterozygous individuals

d.  The frequency of homozygous recessive and heterozygous individuals

e.  The frequency of homozygous dominant and heterozygous individuals

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In the Hardy-Weinberg equation, p + q = 1, p and q represent the frequency of alleles in a population of diploid organisms if: 

a.  Two or more alleles exist for that gene

b.  Two or more genes are needed to express a trait

c.  Only two alleles exist for that gene

d.  The trait is polygenic

e.  Only one allele exists for that gene

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