what are 5 assumptions about the population which must be met to make the hardy-weinberg rule valid

Biology 198
PRINCIPLES OF BIOLOGY
Hardy-Weinberg practice questions

Updated: 21 Baronial 2000

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POPULATION GENETICS AND THE HARDY-WEINBERG Law

The Hardy-Weinberg formulas allow scientists to make up one's mind whether evolution has occurred. Whatsoever changes in the gene frequencies in the population over time can be detected. The police substantially states that if no evolution is occurring, and so an equilibrium of allele frequencies volition remain in effect in each succeeding generation of sexually reproducing individuals. In order for equilibrium to remain in effect (i.eastward. that no evolution is occurring) and then the post-obit five conditions must be met:

1. No mutations must occur and then that new alleles do non enter the population.
2. No gene flow can occur (i.east. no migration of individuals into, or out of, the population).
3. Random mating must occur (i.east. individuals must pair by chance)
4. The population must be big so that no genetic drift (random chance) tin can crusade the allele frequencies to change.
5. No choice can occur and then that certain alleles are non selected for, or against.

Obviously, the Hardy-Weinberg equilibrium cannot exist in existent life. Some or all of these types of forces all human action on living populations at various times and evolution at some level occurs in all living organisms. The Hardy-Weinberg formulas allow usa to detect some allele frequencies that change from generation to generation, thus allowing a simplified method of determining that evolution is occurring. There are two formulas that must be memorized:

p^two + 2pq + qⁱⁱ = ane and p + q = ane

p = frequency of the dominant allele in the population
q = frequency of the recessive allele in the population

pⁱⁱ = percentage of homozygous ascendant individuals
q^two = percentage of homozygous recessive individuals
2pq = percentage of heterozygous individuals

Individuals that have aptitude for math find that working with the to a higher place formulas is ridiculously easy. However, for individuals who are unfamiliar with algebra, it takes some practice working problems before you lot get the hang of it. Below I have provided a serial of practice issues that you may wish to try out. Note that I take rounded off some of the numbers in some bug to the second decimal place:

1. Problem #1.

   Yous have sampled a population in which yous know that the percentage of the homozygous recessive genotype (aa) is 36%. Using that 36%, calculate the following:

   1. The frequency of the "aa" genotype.
   2. The frequency of the "a" allele.
   3. The frequency of the "A" allele.
   4. The frequencies of the genotypes "AA" and "Aa."
   5. The frequencies of the ii possible phenotypes if "A" is completely dominant over "a."
2. Problem #ii.

   Sickle-cell anemia is an interesting genetic disease. Normal homozygous individials (SS) have normal blood cells that are easily infected with the malarial parasite. Thus, many of these individuals become very ill from the parasite and many die. Individuals homozygous for the sickle-prison cell trait (ss) have scarlet claret cells that readily collapse when deoxygenated. Although malaria cannot grow in these red blood cells, individuals often die because of the genetic defect. Notwithstanding, individuals with the heterozygous condition (Ss) have some sickling of ruddy blood cells, simply more often than not not plenty to cause mortality. In addition, malaria cannot survive well inside these "partially defective" red blood cells. Thus, heterozygotes tend to survive better than either of the homozygous conditions. If ix% of an African population is built-in with a astringent form of sickle-cell anemia (ss), what per centum of the population volition exist more resistant to malaria considering they are heterozygous (Ss) for the sickle-prison cell cistron?

3. PROBLEM #3.

   There are 100 students in a grade. Ninety-six did well in the course whereas four blew it totally and received a grade of F. Pitiful. In the highly unlikely event that these traits are genetic rather than environmental, if these traits involve ascendant and recessive alleles, and if the iv (4%) represent the frequency of the homozygous recessive condition, delight calculate the post-obit:

   1. The frequency of the recessive allele.
   2. The frequency of the dominant allele.
   3. The frequency of heterozygous individuals.
4. PROBLEM #four.

   Within a population of butterflies, the color brown (B) is dominant over the color white (b). And, 40% of all butterflies are white. Given this simple information, which is something that is very likely to be on an exam, calculate the following:

   1. The percentage of butterflies in the population that are heterozygous.
   2. The frequency of homozygous dominant individuals.
5. Trouble #five.

   A rather large population of Biology instructors accept 396 ruby-sided individuals and 557 tan-sided individuals. Assume that red is totally recessive. Please calculate the following:

   1. The allele frequencies of each allele.
   2. The expected genotype frequencies.
   3. The number of heterozygous individuals that you would predict to be in this population.
   4. The expected phenotype frequencies.
   5. Weather happen to be really expert this year for breeding and side by side year at that place are one,245 young "potential" Biology instructors. Assuming that all of the Hardy-Weinberg atmospheric condition are met, how many of these would you lot expect to be cherry-red-sided and how many tan-sided?
6. PROBLEM #6.

   A very large population of randomly-mating laboratory mice contains 35% white mice. White coloring is caused by the double recessive genotype, "aa". Calculate allelic and genotypic frequencies for this population.

7. PROBLEM #7.

   Afterwards graduation, you and xix of your closest friends (lets say 10 males and 10 females) lease a aeroplane to go along a round-the-world tour. Unfortunately, y'all all crash land (safely) on a deserted isle. No one finds you and you start a new population totally isolated from the rest of the world. 2 of your friends carry (i.due east. are heterozygous for) the recessive cystic fibrosis allele (c). Assuming that the frequency of this allele does non change every bit the population grows, what will be the incidence of cystic fibrosis on your isle?

8. Problem #8.

   You lot sample one,000 individuals from a large population for the MN blood group, which tin can hands be measured since co-say-so is involved (i.e., you can detect the heterozygotes). They are typed appropriately:

   Blood Blazon	GENOTYPE	NUMBER OF INDIVIDUALS	RESULTING FREQUENCY
   M	MM	490	0.49
   MN	MN	420	0.42
   North	NN	xc	0.09

   Using the data provide to a higher place, calculate the following:

   1. The frequency of each allele in the population.
   2. Supposing the matings are random, the frequencies of the matings.
   3. The probability of each genotype resulting from each potential cantankerous.
9. Trouble #9.

   Cystic fibrosis is a recessive condition that affects most 1 in 2,500 babies in the Caucasian population of the The states. Please calculate the following.

   1. The frequency of the recessive allele in the population.
   2. The frequency of the dominant allele in the population.
   3. The percent of heterozygous individuals (carriers) in the population.
10. PROBLEM #10.

    In a given population, only the "A" and "B" alleles are present in the ABO system; at that place are no individuals with blazon "O" claret or with O alleles in this detail population. If 200 people have type A blood, 75 take blazon AB blood, and 25 take blazon B blood, what are the alleleic frequencies of this population (i.e., what are p and q)?

11. Trouble #11.

    The ability to taste PTC is due to a single dominate allele "T". You sampled 215 individuals in biology, and determined that 150 could detect the bitter taste of PTC and 65 could not. Calculate all of the potential frequencies.

12. PROBLEM #12. (You will non have this type of problem on the exam)

    What allelic frequency will generate twice every bit many recessive homozygotes as heterozygotes?

ANSWERS TO THE QUESTIONS

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