Download name: Lab 2 Population Genetics Quiz Key 1. Define microevolution

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Lab 2 Population Genetics Quiz Key
1. Define microevolution(1pt).
Microevolution is the change in the proportion of alleles in a population over time.
2. You have a population with 10 AA genotypes 20Aa genotypes and 10aa genotypes.
The next generation has 5AA genotypes, 10Aa genotypes, and 5aa genotypes. Did
the population evolve? (1pt)
This population is not evolving. The proportion of alleles is 0.5 A and 0.5 a in the
population at both times. The population is only changing in size.
3. You sample a population and find that is not at Hardy Weinberg equilibrium. List
3 reasons that may have caused the population not to be at Hardy-Weinberg Equilibrium.(3pts)
The population that you examined was not at Hardy-Weinberg equilibrium, therefore one of the hardy-Weinberg conditions must have been violated. You needed to
list 3 of the following conditions.
• The population may be small, violating the assumption of a large population
size.
• You could have had individuals from another population immigrating into the
population or individuals of one type emigrating from the population at a rate
that is not equal to the other types, violating the assumption of no gene flow.
• You could have mutations, violating the assumption that there are no mutations.
• We could have had natural selection, violating the assumption that there is no
natural selection.
• You could have nonrandom mating, where some types mate more frequently
with one type than another violating the assumption of nonrandom mating.
This will not change the proportion of alleles in the population but it will cause
the population to not be at Hardy-Weinberg equilibrium. Violations to all of
the other assumptions can lead to changes in the proportion of alleles in a
population. .
4. You observe a population of 50 individuals with 12 AA genotypes, 29 Aa genotypes,
and 9 aa genotypes (4pts).
(a) Assuming complete dominance and that A is the dominate allele, how many
individuals in your population express the dominant phenotype?
12 + 29 = 41 individuals will express the dominant phenotype.
(b) Calculate the proportion of each of the genotypes that you observed.
The proportion of AA genotypes in the population is 12
= 0.24. The propor50
tion of Aa genotypes of in the population is 29
=
0.58.
The
proportion of aa
50
9
genotypes is 50 = 0.18.
(c) Calculate the proportion of the A allele and the a allele.
53
2∗12+29
= 100
= 0.53. The
The proportion of the big A allele is p = 2∗12+2∗29+2∗9
29+2∗9
47
proportion of the small a allele is q = 2∗12+2∗29+2∗9 = 100 = 0.47
(d) Using the allelic proportions that you calculated above calculate the proportions of genotypes that you would expect under Hardy-Weinburg Equilibrium.
Under Hardy-Weinberg equilibrium we would expect there to be p2 = 0.532 =
0.2809 AA genotypes, 2pq = 2 ∗ 0.53 ∗ 0.47 = 0.4982 Aa genotypes, and
q 2 = 0.472 = 0.2209 aa genotypes.
5. You have a small population of 20 individuals. All of the other conditions for HardyWeinberg equilibrium are met. The population starts with a frequency of 0.5 of the
A allele and 0.5 for the a allele. If the population remains 20 individuals and the rest
of the Hardy-Weinberg conditions continue to hold, what will eventually happen to
the population? (1pt)
A small population will have genetic drift. There will be small changes in the
proportion of alleles in the population from one generation to the next due to chance
occurrences. If enough time passes eventually one of the alleles either the A allele
or the a will be lost, but we don’t know which one. When the population has no
mutation and no migrants bringing in different genotypes the population can’t get
the lost allele back.