Genetics of Taste Worksheet

Class Total Data Chart

PTC taste test paper
Taster / Non-taster
Yourself
Class Data
  1. Using only the data above, would it be possible to determine if “tasters” or “non-tasters” is the dominant phenotype? Explain your reasoning.
  1. It is known that the ability to taste PTC paper is a dominant trait. Knowing this, tell ALL of the possible phenotypes and genotypes of both tasters and non-tasters.
  1. Can we state for certain your genotype for PTC tasting if you have the dominant phenotype? Explain.
  1. What is the name of the process used to figure out the genotype of an individual with a dominant phenotype? Explain this process (Note: This would never actually be used with humans).
  1. An individual who was heterozygous for PTC tasting mated with someone who could not taste PTC paper.

a. Parent phenotypes?

b. Parent genotypes?

c. Punnett square for cross

d. Genotype ratio of offspring

e. Phenotype ratio of offspring

  1. Define(I know you’ve had to define these several times. Hopefully you’re getting the hint that you need to know them):

a)Gene

b)Allele

c)Homologous Chromosomes

d)Law of Segregation

e)Law of Independent assortment

Dihybrid Cross

1. An individual who was heterozygous for being able to roll their tongue and homozygous for tasting PTC paper mated with an individual who could not roll their tongue or taste PTC paper.

a. What are the genotypes of the parents involved in this cross?

b. What are the phenotypes of the parents involved in this cross?

c. Show the Punnett squares for this cross below.

d. Give the phenotype ratio of their offspring.

e. Explain how this ratio can illustrate the law of independent assortment.

f. A parent who is heterozygous for rolling their tongue can have children who can or cannot roll

their tongue. Explain how this demonstrates the law of segregation.

f. How many of their offspring would have the genotype RrTt?

g. How many of their offspring would not be able to roll their tongue but could taste PTC paper?

Additional Questions

Thiourea / Sodium Benzoate
Taster / Non-taster / Sweet / Sour / Salty / Bitter / Other / Non-taster
Yourself
Class Data
  1. Answer the following questions comparing the individuals who were tasters for PTC and tasters for Thiourea.
  2. How do the percentages of tasters vs. non-tasters compare between PTC and thiourea?
  3. Were the tasters the same individuals for both substances?
  4. What does the comparison between the ability to taste PTC paper and Thiourea tell you concerning the law of independent assortment?
  1. How does the ability to taste sodium benzoate compare to the ability to taste PTC or thiourea?
  1. As we have learned, dominant alleles code for a functioning protein while recessive alleles do not. This is why heterozygous individuals only show the dominant phenotype (because it is the only protein being made). The ability to taste sodium benzoate is not a simple dominant/recessive trait like we have studied so far. In other words, if it was as simple as a dominant gene making you taste the paper and a recessive gene not allowing you to taste then all dominant individuals would make the same protein (thus tasting the same taste). Hypothesize how the genetics of tasting sodium benzoate are different as they allow different individuals to taste the same substance differently.
  1. Analyze the statement “The ability to taste is inherited.” What do you think? Defend your answer.