Understanding Evolutionring

Evolution in Small Populations

1. A population originally has 500 males and 500 females, all of whom breed.  A hurricane greatly reduces the population's size to 10 males and 10 females.  The original population had an approximately equal number of blue eye color alleles and brown eye color alleles.  The population after the hurricane has a blue eye color allele frequency of 0.9 and a brown eye color allele frequency of 0.10.  What type of event has this population experienced causing it to become so small and what is the probability that the brown eye color allele will become fixed in this population? If the brown eye does become fixed in this population, which force of evolution is most likely responsible for its fixation?

2. The island "Notsolucky" has experienced devastating catastrophic events within the last few months that have reduced the population size to 50 people.  The genetic disorder, Hurler Syndrome, is more prominent in the next generation of children from the survivors and now appears to have equal fitness to the phenotype that displays no signs of the disease.  How would we now describe the fitness state of the Hurler allele and which evolutionary force is responsible for this characteristic?

3. In the article by Sandeep et al. 2013 on conservation of Bengal tigers in India, how did the authors demonstrate that maintaining gene flow between the different tiger preserves was important to promoting a healthy level of genetic variability in each tiger reserve population?  What is drift-migration equilibrium and why is it important to maintaining genetic diversity?  How will it help Bengal tigers in India from going extinct?

4. If the strength of directional selection (S) is 0.10, how large must the effective population size (Ne) be before selection can overcome the effects of genetic drift and drive the favored allele to fixation?  What if S = 0.01; S = 0.001?  Model these in allele A1 and save screen shots or just draw the graphs on your homework.

5. The frequency of two alleles, F and f, in each of three populations of Dalmatians is 0.25 and 0.75. 

a. What are the genotype frequencies in a population with an inbreeding coefficient of 0?

b. What are the genotype frequencies in a population with an inbreeding coefficient of 0.50?

c. What are the genotype frequencies in a population with an inbreeding coefficient of 0.90?

d. What happens to all three genotype frequencies as inbreeding increases?