Here is the entire lab- It's split into 5 experiments. You're supposed to use colored beads but you can use anything you want. I just need all the questions answered. Thanks!
Concepts to Explore
Evolution, Selective pressures, Non-selective pressures, Hardy-Weinberg principle, Gene pool, Gene frequency , Genetic variation , Genetic drift , Founder effect , Mutation , Allelic frequencies in a population
The gene pool is the sum of all genes and their corresponding alleles in a given population. Take a look at the population of 100 brown and white mice in Figure 1. The brown color is dominant. The standard for naming alleles is to use an upper case letter for the dominant allele, and a lower case for the recessive allele. For example, the dominant color (brown) is represented with a B, and the recessive color (white) is represented with a b.
Gene frequency refers to how many times each allele is found in the population. These 100 mice have 200 genes:
• 55 heterozygous mice (B, b) have 55 B alleles and 55 b alleles.
Figure 1: Mouse Population
• 18 homozygous dominant mice (B, B) have 36 B alleles (18 x 2 “B” = 36).
The gene frequency of the population is: B: 91 b: 109 and that they are all homologous.
Often, this is represented as a percentage of the dominant gene. In this case, the percentage of B is 45.5% (=91/200). Note that the dominant gene is less prevalent than the recessive gene. This is not unusual. It is important to remember that dominance has no direct relation- ship to prevalence.
To estimate the frequency of alleles in a population, we can use the Hardy-Weinberg equa- tion. According to this equation:
p = the frequency of the dominant allele (represented here by A) q = the frequency of the recessive allele (represented here by a)
Note: In the exercises on gene pool gene frequency, and genetic diversity; assume there are four alleles for color
Lab 4: Population Genetics and Evolution For a population in genetic equilibrium:
p + q = 1.0 (The sum of the frequencies of both alleles is 100%.) (p+q)2 =1
So p2 +2pq+q2 =1
The three terms of this binomial expansion indicate the frequencies of the three genotypes:
p2 = frequency of AA (homozygous dominant) 2pq = frequency of Aa (heterozygous) q2 = frequency of aa (homozygous recessive)
Pre-Lab Questions
1. What is the gene pool of this population (shown in the pie chart on the right)?
2. What is the gene frequency (use the Hardy-Weinberg equation)?
Materials
• Blue beads, Red beads, Green beads, Yellow beads, 2 100 mL Beakers, 2 250 mL Beakers
Questions
1. What is the gene pool of beaker #1?
2. What is the gene pool of beaker #2?
3. What is the gene frequency of beaker #1?
4. What is the gene frequency of beaker #2?
5. What can you say about the genetic variation between these populations?
Experiment 2: Genetic Drift
Genetic drift, the variation of the gene pool and/or gene frequency of a population, can result from a variety of stochastic (random) means. Consider the following population of butterflies who have half of their habitat destroyed by wildfire (Figure 3):
Figure 3: Butterfly populations before and after wildfire.
The remaining population has 50% of the initial gene pool (two colors) and the gene frequency is different. As these individuals reproduce, their offspring will no longer reflect the original population.
Materials
Blue beads, Red beads, Green beads, Yellow beads, 100 mL Beaker, 250 mL Beaker
Procedure:
From the 250mL beaker containing green and yellow beads, take 10 beads and place them into the unused 100 mL beaker (this is beaker #3).
Randomly remove half of the beads from beakers #1, #2, and #3 . These are the individuals that survived the fire. (Keep them separated so they can be returned to their proper beaker. You will use them again in the next lab.)
Record your results and place the beads back in their respective beakers.
Repeat this process four more times (five total).
• Do the results vary between the populations represented by beakers #1, #2 and #3? Why or why not?
• What observations can you make about the genetic variation between the parent and surviving populations?
Experiment 3: Stochastic Events
• Consider the same population of butterflies is in the path of a hurricane. All survive, but 10 are blown to a new location. These 10 start a new population; their progeny will reflect the founder’s gene pool. This is known as the founder effect.
Materials
Beaker #1 Beaker #2 Beaker #3
Procedure:
Remove 10 individuals from beaker #1, five from beaker #2 and two from beaker #3. The- se are the founders of your new population.
Record your results and place the beads back in their respective beakers.
Repeat this process four more times (five total).
Questions
1. What observations can you make regarding the gene pool and gene frequency of the founding individuals?
2. Do these results vary between the populations founded by beakers #1, #2 and #3? Why or why not?
3. What observations can you make about the genetic variation between the parent and founding populations?
4. Suppose you have a population of 300 butterflies. If the population grows by 12% in the following year, how many butterflies do you have?
5. Now suppose you have 300 eggs, but only 70% of those eggs progress to become a cater- pillar, and only 80 of the caterpillar progress to become an adult butterfly. How many butterflies do you have?
6. 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?
Pre-Lab Questions
• In the mammalian genome: 1. How many total basepairs are in all the mammalian genes? 2. What proportion (%) of the total genome does this represent? 3. What is the probability that a random mutation will occur in any given gene? 4. What is the probability that a random mutation will change the structure of a protein? Nonetheless, some mutations do change the protein coded for by a gene. The vast majority of these mutations are lethal and the embryo never fully develops. Occasionally mutations do not effect embryonic development and the offspring is born without complication.
Experiment 4: Natural Selection
Natural selection is a selection pressure that affects phenotypes in one of three ways:
• It will create an adaptive advantage.
• It will create an adaptive disadvantage.
• It will remain entirely neutral.
A classic example to illustrate natural selection comes from England. Prior to the Industrial Revolution, the native moths were normally a light color, though darker versions of the same species existed. The lighter color blended with the light bark of the local trees, while the darker moths experienced a higher predation rate – they were easier for birds to spot and fewer survived to reproduce. As England entered the Industrial Revolution they began burning fossil fuels with little regard to the pollutants they were emitting. The trunks of the trees became coated with soot and their color darkened. The lighter moths became more conspicuous and the darker moths were better camouflaged. The proportion of white to dark moths changed.
Materials
Procedure:
Print out the two sheets of paper marked Blue Habitat and Red Habitat, from your manual (found at the end of this lab).
Place 50 red and 50 blue beads into a 100 mL beaker.
Mix them well and pour them onto the sheet marked Red Habitat.
Keep the beads that fall onto the habitat that matches their color.
For each bead that you keep (and return to the beaker), add another bead of the same col- or to the beaker (discard the rest).
Repeat this three times.
Record the remaining colors. Blue _____________ Red _____________
Do you observe a selective advantage for the red or blue beads? Why? WITH THE REMAINING BEADS, repeat the process using the Blue Habitat.
What beads remain? Blue _____________ Red _____________
Questions
1. How did the distribution of phenotypes change over time?
2. Is there a selective advantage or disadvantage for the red and/or blue phenotypes?
3. What phenotypic results would you predict if starting with the following population sizes?
4. A. 1000: B. 100: C. 10:
5. Assume that you live in a country with 85 million people that consistently experiences an annual growth rate of 4.2%. If this population continues to grow at the same rate for the next 50 years, how many people will live in the country (round to the nearest whole number).
Experiment 5: Sickle Cell Anemia
Sickle cell anemia is a genetic disease (1 base pair mutation that changes a protein). It is common in those of African ancestry. “S” will represent the normal dominant allele and “s” the recessive sickle allele. They are co-dominant alleles – SS is normal, Ss is not fatal, ss is debilitating, painful and often fatal.
Materials
Blue beads, Red beads, 100 mL Beaker
Procedure:
Place 25 red (S) and 25 blue (s) beads into the 100 ml beaker and mix well.
Randomly (without looking) remove two beads. Repeat 10 times (without returning the beads to the beaker), each time recording if it was a SS, Ss or ss.
Remove each ss from the population – they died.
The remaining beads survived and reproduced.
Count how many red and blue beads remained (separately) and place twice that number back in the beaker.
Repeat the process seven times.
Questions
1. What is the remaining ratio of alleles?
2. Have any been selected against?
3. Given enough generations, would you expect one of these alleles to completely disappear from the population? Why or why not?
4. Would this be different if you started with a larger population? Smaller?
5. After hundreds or even thousands of generations both alleles are still common in those of African ancestry. How would you explain this?
6. The worldwide distribution of sickle gene matches very closely to the worldwide distribution of malaria (http://cdc-malaria.ncsa.uiuc.edu/). Is this significant? Why or why not?
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