Koi Fish Hardy-Weinberg PDF

Preview

Summary

Download Koi Fish Hardy-Weinberg PDF

Description

Name ____Oyinda Adeyemo____

2021______

LAB EXERCISE 3:

Fish-Pond Populat Introduction

Introduction Evolution is defined as a change in the frequencies of alleles in a population. Note that a change that influences phenotypic or genotypic frequencies, while not changing allelic frequencies, would therefore not cause that population to evolve. To understand how a population can be changed, we must first understand a population that is not changing (and is therefore in a state of equilibrium). During today’s lab you will be simulating changes in a virtual population of koi fish. Color in this particular variety of koi is controlled by a single gene, for which there are only two alleles (R = orange and r = white). But, because these alleles are codominant, heterozygotes are both orange and white with a “mottled” appearance. This gives us three possible genotypes with three distinct phenotypes. So…

Individuals that are homozygous recessive have the genotype rr and the phenotype:

Individuals that are homozygous dominant have the genotype RR and the phenotype:

Individuals that are heterozygous have the genotype Rr and the phenotype:

Question 1: If the gene for color in this example were NOT codominant, what would the heterozygous koi fish look like? ________Rr Rw________

Materials This example gives us an opportunity to study how various factors affect the frequencies of alleles in a population. To do this, we will use a simulator created by Virtual Biology Lab, which can be found using the following web address:

http://virtualbiologylab.org/ModelsHTML5/PopGenFishbowl/PopGenFishbowl.html Experiment Activity 1: Background Click on the link for “Background Information”. Read the section on Population Genetics and answer the following question. Question 2: In your own words, what is the difference between macroevolution and microevolution? Which one are we studying today? Microevolution is the process of change from one generation to another over a period of time while macroevolution is the resulting pattern of these long term changes Read the section on Hardy-Weinberg Equilibrium and answer the following questions. Question 3: According to the website, what are the 5 conditions that might cause proportions of alleles and genotypes to change from generation to generation? (note that the website lists 5 things that are required for a population to NOT change) 1. 2. 3. 4. 5.

______Insufficient population_______ ______Immigration or emigration of the population_________ ______Mutation________ ______Selective mating_______ ______Unfit genotype_________

This section also gives us our first glimpse of the variable used in Hardy-Weinberg formula. In the koi pond example, explain what each of the following represent: Question 4: p=

_______dominant (R) allele________

q =.

________recessive (r) allele_________

p2 =

_______ dominant homozygous frequency (RR)_________

2pq = ________ heterozygous frequency (Rr)______________ q2 =

_________ recessive homozygous frequency (rr)__________

Read over each of the evolutionary mechanisms in the next section. Explain (again, using your own words) the following mechanisms:

Question 5: Genetic drift = Change in the frequency of an allele as time changes Migration =

Movement of individuals in or out of a population

Non-random mating = Process where an individual picks a mate similar to its own genotype or phenotype

Read the final two sections in the background. While recommended that you also read the tutorial secti Activity 2: Run Experiments Experiment 1: Migration Let’s see how new individuals entering the pond c population. For this experiment, set the following acc -Set the migration rate to 0.5 -Set the proportion of migrants with the R -Set the speed to 16X -Note that the initial ‘R’ allele frequency is s

(meaning the r and R alleles are both balanced at 50%) Run the simulation for 250 generations. Sketch the results of the allele pr

Fill in the following table using the data in the data collection tab:

Question 6: Did the genotypic frequencies change? Yes Question 7: Did the allelic frequencies change? No Question 8: Did the population evolve? (EXPLAIN). Yeah, the population evolved. At generation 0, we could see an equal amount of heterozygous individuals and homozygous dominant individuals and as the generations went by, the heterozygous individuals began to decrease while the homozygous dominant individuals increased.

Experiment 2: Relative Fitness Now, let’s see how giving an advantage t genetics of our population. For this experim -Set the migration rate to 0.0. (no -Set the relative fitness for the rr -Set the relative fitness for the Rr -Set the relative fitness for the RR -Set the speed to 16X -Again, note that the initial ‘R’ allele

Run the simulation for 250 generations.

Sketch the results of the allele proportion graph

Fill in the following table using the data in the data collection tab:

e

Question 9: Did the genotypic frequencies change? Yes Question 10: Did the allelic frequencies change? Yes Question 11: Did the population evolve? (EXPLAIN). No. The population did not evolve. By the 250th generation, there were still some heterozygous individuals amongst the homozygous recessive individuals. Experiment 3: No Selection, No Migration Finally, what happens if there are no fitness advantages and no sources of new alleles? What happens if we take ALL of the sources of change out, and only modify the population size? -Set the initial population size to 25 (very small -Set the carrying capacity to 25 -Make sure all other settings are normal

Question 12: What do you PREDICT will happen in this small population without any outside sources of genetic change? Will allelic frequencies remain steady at 0.5 or change in any particular direction? I think the allelic frequencies would remain steady.

Low Population Run 1

Low Population Run 2

Low Population Run 3

Question 13: Were the results consistent across the three runs? Did the populations evolve? No, the result was not consistent. The evolution evolved. Now, change the population settings and run again -Set the initial population size to 500 (ver -Set the carrying capacity to 500 -Make sure all other settings are normal Question 14: What do you PREDICT will happen this time with a much larger population, but not outside sources of genetic change? Same thing as before or a different result? (Explain your reasoning) Different results, there would be a genetic variation among the fish since it’s a larger population and rr, Rr & RR are similar ratio.

High Population Run 1

High Population Run 2

High Population Run 3

Question 15: Were the results consistent across the three runs? Did the populations evolve? The results were not consistent. The population did not evolve.

Question 16: What evolutionary mechanism could possibly explain any genetic changes you observed in the koi population? Non-random mating

Question 17: Explain the differences you observed between the low population runs and the high population runs. In the high population, the homozygote individuals remained throughout from generation to generation while in the low population there was no homozygote individual or homozygous dominant by the 250th generation...