Using the class as a sample population, the allele frequency of a gene controlling the ability to taste the chemical PTC (phenylthiocarbamide) can be estimated. A bitter taste reaction is evidence that the dominant allele is present, though the person could be TT or Tt. Inability to taste PTC means the individual is tt.
You will also calculate the frequency of individual who can roll their tongue, which is also determined by a dominant allele: either TT or Tt. Those who can't roll their tongues are tt.
After surveying the class, determine the frequency by dividing the number of those with the trait, by the total number in the class.
| Phenotypes | ||||||
| Tasters (p2) | Tasters (2pq) | Non Tasters (q2) | Tongue Rollers (p2) | Tongue Rollers (2pq) | Non Tongue Rollers (q2) | |
| Class Population | ||||||
| North American Population |
0.11
|
0.44
|
0.45
|
.17
|
0.48
|
0.35
|
Hardy-Weinberg Problems (SHOW ALL WORK)
1. In Drosophila (fruit fly), the allele for normal wing length is dominant over the allele for short wings. In a population of 1000 individuals, 360 show the recessive phenotype. How many individuals would you expect to be homozygous dominant for the trait.
2. The allele for a widow's peak (hairline) is dominant over the allele for a straight hairline. In a population of 500 indiviuals, 25% show the recessive phenotype. How many individuals would you expect to be homozyous dominant and heterozygous for the trait?
3. The allele for a hitchhiker's thumb is dominant over a straight thumb. In a population of 1000 individuals, 510 show the dominant phenotype. How many individuals would you expect for each of the three possible genotypes for this trait.
4. 1. If 9% of an African population is born with a severe form of sickle-cell anemia (ss), what percentage of the population will be more resistant to malaria because they are heterozygous(Ss) for the sickle-cell gene?
5. This is a classic data set on wing coloration in the scarlet tiger moth (Panaxia dominula). Coloration in this species had been previously shown to behave as a single-locus, two-allele system with incomplete dominance. Data for 1612 individuals are given below:
White-spotted (AA) =1469 Intermediate (Aa) = 138 Little spotting (aa) =5
Calculate the allele frequencies ( p and q )
6. After graduation, you and 19 friends build a raft, sail to a deserted island, and start a new population, totally isolated from the world. Two of your friends carry (that is, are heterozygous for) the recessive cf allele, which in homozygotes causes cystic fibrosis. Assuming that the frequency of this allele does not change as the population grows, what will be the instance of cystic fibrosis on your island?
SCHOOL SURVEY
In humans, the allele that causes the big toe of the foot to be slightly shorter than the second toe is a dominant allele. Some have a big toe that is longer than the second toe, though this is a recessive trait (tt). Conduct a survey of your school and determine the allele frequencies of TT, Tt, and tt.
Number Surveyed ___________
Short big toe ____________
Long big toe ____________