- There are approximately 3,000,000,000 base pairs in the mammalian genome (genes constitute only a portion of this total).
- There are approximately 10,000 genes in the mammalian genome.
- A single gene averages 10,000 base pairs in size.
- Only 1 out of 3 mutations that occur in a gene result in a change to the protein structure.
In the mammalian genome:
- How many total base-pairs are in all the mammalian genes?
- What proportion (%) of the total genome does this represent?
- What is the probability that a random mutation will occur in any given gene?
- What is the probability that a random mutation will change the structure of a protein?
Experiment 1: Genetic Variation
- What is the initial gene pool of beaker #1?
- What is the initial gene pool of beaker #2?
- What is the initial gene frequency of beaker #1?
- What is the initial gene frequency of beaker #2?
- What can you say about the genetic variation between these populations?
- What is the new gene pool of beaker #1?
- What is the new gene pool of beaker #2?
- What is the new gene frequency of beaker #1?
- What is the new gene frequency of beaker #2?
- What can you say about the genetic variation between these populations after mixing?
Experiment 2: Genetic Drift
- What observations can you make regarding the gene pool and gene frequency of the surviving individuals? How does this change with multiple trials?
- Do the results vary between the populations represented by beakers #1 and #2? Why or why not?
- 3. How will the removal of individuals from the different populations affect the genotypes of future generations? How is this different from the genotypes that would have resulted if those individuals had not been removed?
- Suppose you have a population of 300 butterflies. If the population experiences a net growth of 12% in the following year, how many butterflies do you have?
- Now suppose you have 300 eggs, but only 70% of those eggs become caterpillars, and only 80% of the caterpillars become adult butterflies. How many butterflies do you have? (For simplicity, assume that all butterflies survive to the next year in this example.)
- Suppose you have a population of 150 butterflies, but a wildfire devastates the population and only 24 butterflies survive. What percent does the colony decrease by?
Experiment 4: Natural Selection
Distribution of colors after Step 6:
Do you observe a selective advantage for the red or blue beads? Why?
Distribution of colors after Step 7:
- How did the distribution of phenotypes change over time in the two different environments?
- For the two different environments, is there a selective advantage or disadvantage for the red and/or blue phenotypes?
- What phenotypic results for each environment would you predict if starting with the following population sizes?
Experiment 5: Sickle Cell Anemia Inheritance Patterns
- What is the final ratio of alleles?
- Were either of the alleles selected against?
- Given enough generations, would you expect one of these alleles to completely disappear from the population? Why or why not?
- Would this be different if you started with a larger population? Smaller?
- After hundreds or even thousands of generations both alleles are still common in those of African ancestry. How would you explain this?
- The worldwide distribution of sickle gene matches very closely to the worldwide distribution of malaria (see images below). What is the significance of this?