Download How does natural selection affect gene frequency over several

How does natural selection affect gene frequency over several generations?
Due to winter bunnies with no fur won't survive, so there will be increase in the number of
bunnies with FF genes, or bunnies with fur.
Clearly state your hypothesis (a tentative explanation or solution to the problem).
Our hypothesis is that after the experiment and after natural selection the furless bunnies will
die and only dominant alleles (bunnies with fur) will be left.
State what you would predict (if your hypothesis is true) about the frequency of F alleles and f
alleles in the population of rabb’its after 10 generations, where ff bunnies are selected against
(do not survive).
There will be a higher of F alleles than f alleles.
Generation Number of Number of Number of Number Number Total
Gene
Gene
FF
Ff
ff
of F
of f
number frequency frequency
individuals individuals individuals alleles
alleles
of
of F
of f
alleles
1
15
20
14
50
49
100
51/100
49/100
2
22
6
8
50
22
72
44/72
22/72
3
23
4
1
50
6
56
50/56
6/56
4
24
2
1
50
4
54
50/54
4/54
5
25
0
1
50
2
52
50/52
2/52
6
7
8
9
10
Discussion Questions
Introduction (Claudia):
In this lab we were observing natural selection. Over time the number of alleles in a
generation would change which results in evolution. This would happen because there are
genetic traits that would either be helpful or damaging to a species throughout its life, therefore
the damaging traits would die off leaving only the helpful ones. For example in this lab we are
looking at rabbits. Specifically we are looking at the traits of fur vs. no fur. The trait for fur is
dominant (F), and furless is recessive (f).We tossed 50 red beads - representing the fur trait and 50 white beads - representing the furless trait - and mixed them together in a bowl. From
there we went on to pull out pairs that came out of the “mating” process and recorded our data.
Abstract (Payne):
The Hardy-weinberg theory was explored using rabbits with fur or no fur as an model.
(the rabbits were represented as beads in this experiment.) The allelic frequency in our bunny
population was examined by randomly choosing two alleles and creating a phenotype of a
bunny with it. It was noted that the recessive alleles are slowly receding and taken out of the
population. The dominant genotype and phenotypes appeared more frequently as the hairless
bunnies (homozygous recessive, hairless) died out. This data suggests that eventually
recessive genes will be eliminated from the population, and has only been shown due to the
equation set forth by Hardy-Weinberg.
Methods (Richard):
The way we went about conducting this experiment was simple. All we needed was 100
beads,split half and half with two different colors, a bowl, and a 9 by 11 chart. We noted that the
50 red beads were representing alleles for the bunnies with fur, and the white bunnies
represented hairless bunny alleles. In ten trials consisted of one of us closing our eyes and
grabbing two beads. There were three possible combinations for the Als and there were three
separate trays for each respective combination. If two red beads were drawn it went in tray one,
which represented the dominant fur bunny allele. If one red and one white bead were drawn the
beads would go in tray two, representing the mixed fur bunny. But, if two whites were drawn,
the whites would go on tray three, be noted as hairless bunnies, and unlike the other two Als,
the recessive Als wouldn’t be put into the bowl again for the upcoming trial. So eventually, there
were only 50 beads, all red, that were in the bowl for the trials.
Results (Claudia):
After doing this experiment we came up with these results.
Generation Number of Number of Number of Number Number Total
Gene
Gene
FF
Ff
ff
of F
of f
number frequency frequency
individuals individuals individuals alleles
alleles
of
of F
of f
alleles
1
15
20
14
50
49
100
51/100
49/100
2
22
6
8
50
22
72
44/72
22/72
3
23
4
1
50
6
56
50/56
6/56
4
24
2
1
50
4
54
50/54
4/54
5
25
0
1
50
2
52
50/52
2/52
The 1st generation was naturally without a winter to kill the ff alleles. Then from there on the
other generations there was a harsh winter that would kill the ff alleles, therefore every
generation the numbers of f alleles would lower. Then in the 5th generation after this one there
would be no f alleles left and there would only be furred rabbits left.
Discussion (Richard):
Our group and I figured that, even though there was an even number of both colors of
beads, the white ones wouldn’t be present in the bowl around trial six or seven. We noted that
even though the white ones would be taken out, eventually making it less likely to get a pair, the
white beads were bigger than the red ones, making it apparent that those had a better chance
of being picked.
1. What was your original hypothesis?
2. Based on your lab data, do you need to change your hypothesis? Explain.
3. Compare the number of alleles for the dominant characteristic with the number of alleles
for the recessive characteristic.
4. Compare the frequencies of the dominant allele to the frequencies of the recessive
allele.
5. In a real rabbit habitat new animals often come into the habitat (immigrate), and others
leave the area (emigrate). How might emigration and immigration affect the gene
frequency of F and f in this population of rabbits? How might you simulate this effect if
you were to repeat this activity?
6. How do your results compare with the class data? If significantly different, why are they
different?
7. How are the results of this simulation an example of evolution?
Conclusion (Solka):
In this lab we observed simulated natural selection in a small population of wild rabbits.
The dominant trait of the rabbits is fur (red allele) and the recessive trait of the rabbits is fur-less
(white allele). Homozygous furless rabbits (white-white alleles) are not able to survive because
of the winter, while heterozygous red-white rabbits and red-red rabbits will survive the winter
and live on to reproduce the next generation of rabbits. Our hypothesis matched the actual
results of the experiment.