Page Lab 10. Genetie drift Genetic drift is the change in allelic frequency due

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Page Lab 10. Genetie drift Genetic drift is the change in allelic frequency due to random sampling. Some alleles can disappear from a population solely due to the effects of genetic drift. It can have its most severe effects in small populations, or when small numbers of alleles are passed to the next generation. When there are fewer copies of an allele the effects of drift are larger than when there are many copies of an allele. In today's lab we are going to carry out a sampling exercise to look at the effects of genetic drift as different numbers of alleles are passed on from one generation to the next. Exercise 1. Start with 40 buttons, 20 white and 20 black (i.e. a 50:50 ratio, or allelic frequencies of 0.500 for the white allele and 0.500 for the black). Shake them up in your hand then squeeze out 20 buttons onto the desk. Count the numbers of each button and record the allelic frequencies of the two colored buttons. If the frequencies are still 0.500 and 0.500, record this and then repeat the exercise. If, however, the ratio is not 0.500 white and 0.500 black, record the frequencies of the two different alloles. Then, you need to adjust the number of black and white buttons in the 40 buttons to match that frequency, because this represents the number of buttons going into the next generation. For example if the ratio was 0.600 white and 0.400 black, you would have 24 white button and 16 back buttons going into the next generation. Then squeeze out 20 buttons and record the allelic frequencies again. Keep doing this and record the allele frequencies, recording the allelic frequencies for up to 20 generations, but remembering to change the number of buttons each time to reflect the frequency of the buttons that resulted from the previous generation. If you get to a point when you have a frequency of 1.000 of one button (i.e. all buttons are of one color, then record that and stop. Now one allele has been eliminated by genetiç drift (random sampling) alone. Graph you data showing the frequency of each allele over the generations in a figure. Exercise 2. This is similar to exercise 1, starting with 40 buttons, 20 of each color, except instead of this time squeeze out 10 buttons each generation. Then record the allelic frequencies, and adjust the number of buttons to reflect this frequency going into the next squeezing out 20 buttons, 30

Explanation / Answer

1) Allele frequency

2)

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