B.What proportion of the herd is likely to be heterozygous? 50%

C.The owner then separates all those animals showing crinkly-hair and sends them for slaughter.He allows the remaining animals to breed freely.What proportion of the next generation of lambs would be expected to show crinkly hair? 1/9

2.If, in a sample of people from Birmingham, 22% were found to be of blood group N, what, approximately, would be the expected percentages of the M and MN groups? M 28.2%, MN 49.8%

3.A packet of Nicotiana seeds was bought from a seedsman and, when the seeds germinated, 192 seedlings were albino and 2880 were green.

A.What proportion of the seedlings would be expected to be homozygous for chlorophyll production?56.25%

B.What proportion of the seedlings would be expected to be carriers of the albino gene?37.5%

4.A recessive lethal gene in chickens causes circulatory failure and death of the embryo at 70 hours.A commercial hatchery finds that a hatching failure due to this gene of greater than 4% is unacceptable.What is the upper limit for the frequency of this allele in the breeding population of fowls that is acceptable to the hatchery managers?0.2

5.The alleles for red and white coat color in cattle show absence of dominance, the heterozygote being roan.

A.In a freely breeding herd of 1000 head how many would you expect to be of each coat color if the allele for white coat has a frequency of 0.4?Red: 36%, Roan 48%, White 16%

B.If all the white cattle were sold for slaughter and the red and roan animals were allowed to breed freely, about what percentage of the offspring would be expected to be white? 8.2%

6.In a sample of 2400 births at a maternity hospital, six babies died shortly after birth from the effects of a recessive gene (co) for colonic obstruction.

A.What is the frequency of this gene in the population?0.5

B.What proportion of the population is heterozygous and what proportion is homozygous for the normal allele? Heterozygous: 9.5%; Homozygous normal: 90.25%

7.In a randomly mating population of Drosophila three alleles for the white-eye locus were known to be present in the following percentage frequencies:

w⁺ (wild type, red eye)20%

w^a (apricot eye)8%

w (white eye)72%

Phenotypes associated with each genotype are as follows:

w⁺w⁺ , w⁺ w^a , w⁺w - red 36%

w^a w^a - apricot 0.64%

w^aw - light apricot 11.52%

ww - white 51.84%

What percentages of the various eye colors would you expect to find in the population?

8.A rancher decided to raise cattle in an isolated valley and bought 1000 head which he transported to the valley to establish a randomly mating population.When released, the animals consisted of 130 white-coated beasts, 330 red, and 540 roan.

A.Does this represent a population in equilibrium?No

B.What will be the proportions of coat color in the next generation?Red 36%, roan 48%, white 16%

C.Is this second generation in equilibrium?Yes

9.In a certain population the following gene frequencies were observed:

I (blood group O) 0.775

M 0.45

Rh⁺ 0.6

What percentages of the population would be expected to have the following blood groups?

A.ORh^-9.61%

B.O MN 29.73%

C.O MN Rh⁺ 24.97%

10.Because a nurseryman finds that his customers generally prefer antirrhinum flowers that are red or pink, he plans that the seeds provided for sale shall contain as few seeds for white flower as possible.He samples his antirrhinum plot which has been established for some years, pollinates randomly, and finds that 9% of the plants have white flowers.He uproots these plants. Next year the remaining red and pink flowers pollinate freely and he collects their seed for marketing.

A.What proportion of the seeds he sells will subsequently produce plants with white flowers?5%

B.How could he obtain an antirrhinum plot that never gives “white-flower” seeds?Red x Red

C.Can he obtain a plot that gives only red and pink flowers?No.

11.Three alleles for the C locus (coat color) in the rabbit are c (albino), which is recessive to c^ch (chinchilla coat), which in turn is recessive to C (the allele for full coat color).In a randomly mating population of rabbits the following gene frequencies were determined:

C 0.2

c^ch0.6

c0.2

What proportions of coat color (expressed as percentages) would you expect to find in that population?Full color 36%, chinchilla 60%, albino 4%

12.In a different population of rabbits a further allele of the C locus was present, namely c^h (Himalayan coat).This allele is dominant to c (albino) but is recessive to the other alleles.The frequencies of the alleles were:

C0.2

c^ch0.3

c^h0.3

c0.2

What percentages of coat color would you expect in this population?Full color 36%, chinchila 39%, Himalayan 21%, albino 4%

13.A mink rancher has a randomly breeding population of animals but decides to prevent those animals which show a barred fur pattern (due to a recessive gene b) from mating, since this fur is less valuable commercially.Initially the barred animals make up 9% of his population.What proportion of barred animals will he obtain 

A.In the next generation?

B.After five generations?
 

	p	q	p2	2pq	p2
start	0.83	0.17	0.68	0.29	0.03
1st gen.	0.85	0.15	0.73	0.25	0.02
2nd gen.	0.87	0.13	0.76	0.22	0.02
3rd gen.	0.89	0.11	0.79	0.20	0.01
4th gen.	0.90	0.10	0.81	0.18	0.01
5th gen.	0.91	0.09	0.82	0.17	0.01

14.A recessive mutation causes short sightedness (ss) in cats.The frequency of homozygous wild type (+/+), heterozgous (+/ss) and homozygous recessive (ss/ss) individuals was assessed in two populations of cats.
 

	+/+	+/ss	ss/ss
country cats	0.49	0.42	0.09
City cats	0.52	0.45	0.03

A.Are the two populations in Hardy-Weinberg equilibrium? Country cats - yes; city cats - no

B.If one population is not, what might cause this deviation? City cats probably can’t breed freely - since many are kept in the house.There may also be migration (purchases from pet store) or breeder selection at play.

15.For an X-linked trait, 9% of the females in the population are affected.What percentage of the males would be affected?What percentage of the population would be represented by carriers?For sex-linked traits, the frequency of male genotypes differs: freq. of dominant genotype is p, frequency of recessive phenotype is q.Thus, 30% of males would be affected, and 42% of females would be heterozygous carriers.

16.You have been commissioned to study the genetic make-up of an ancient tribe of Arabs whose descendents live in northern Saudi Arabia.They hire you to test for the frequencies of a number of well-known genetic traits.The only hitch is that these people won’t let any outsiders go near the women.“No problem,” you say, “as long as I can test the men to determine allele frequencies, I can figure out the gene frequencies in women.That is, if the mode of inheritance is known, and if we can assume Hardy-Weinberg equilibrium.”Prove you can by filling in the empty boxes.

 

trait	mode of inheritance	frequency of trait in males	p	q	frequency of trait in females
PTC taster	autosomal dominant	0.75	.5	.5	.75
blue eyes	autosomal recessive	0.09	.7	.3	.09
color-blindness	X-recessive	0.05	.09	.05	.0025
Xg blood type	X-dominant	0.4	.4	.6	.64
pattern baldness	autosomal dominant in males, recessive in females	0.36	.2	.8	.04

For questions, comments and additional information, contact  mfhicks@pstcc.edu
Last Updated: July 8 2001
Site map: Margaret F. Hicks Home - Biology 2120 - Notes - Hardy-Weinberg Solutions

 
 

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