1. Define the following terms and
utilize these terms in an appropriate context:
allele frequency
assortive mating
coefficient of inbreeding genetic drift
disruptive selection
fitness
gene pool
hybrid vigor
genetic equilibrium
genetic variability
Hardy-Weinberg law
population
inbreeding
migration
natural selection
gradualism
selection coefficient
stabilizing selection allopatric
speciation speciation
punctuated equilibrium
directional selection
race
2. Define population and compare
the types of mating systems prevalent in natural
populations as well
as laboratory populations.
3. Using the MN blood groups as an
example of inheritance controlled by semidominant
alleles, and given
the phenotype frequency, calculate the gene frequencies in a population.
4. Again using the MN blood groups
as an example, and given the gene frequencies,
calculate the probability
of any phenotype occurring.
5. Describe a Hardy-Weinberg equilibrium,
and explain the conditions necessary for a
population to be in
such an equilibrium.
6. Given the phenotype frequencies
in a population, calculate the gene frequencies of
autosomal dominant
and recessive alleles, and the frequencies of homozygous dominant
and heterozygous genotypes.
7. Given the phenotype frequencies
in a population, calculate the frequencies of sex-linked
dominant and recessive
alleles.
8. After determining the allele frequencies
for a sex-linked character, determine the
frequencies of male
and female genotypes in a population of a given size.
9. Modify the expansion of the Hardy-Weinberg
principle to calculate the allele frequencies
of a multiple allelic
circumstance such as blood types A, B and o.
10. Explain that the process of evolution
requires conditions that produce change in allele
frequencies and which
generate genetic variation.
11. Using a formula for mutational
rates in a population determine the mutational rate of a
population. Determine
how many generations might be required to influence existing allele
frequencies.
12. Examine, using the expression
1/2N, how genetic drift effects the fixation rates for alleles
in various sizes of
populations.
13. Determine the rate of fixation
for differing population sizes when the existing allele
frequencies are previously
known.
14. Determine mathematically the effects of selection on allele frequencies.
15. Explain how mutation and migration
introduce new alleles into a population. Highlight
the fact that these
new alleles are retained or lost depending on the fitness conferred by
these alleles and by
the action of selection.
16. Calculate the coefficient of
inbreeding using a human pedigree showing consanguineous
matings within the
pedigree.
Resources: Text Chapter 23, 24
Genetics and Evolution
Hardy-Weinberg:
Populations remain constant if:
random mating
no mutation
no change in population due to migration
large population
no selection pressures + or -
But. . . . . populations and allele
frequencies do change leading to modification, defining the
process of evolution.
4 Processes:
1. Mutation-
origin of new genotype and phenotypes spontaneously in the pop; heritable,
beneficial change
2. Migration- movement of new alleles into or old alleles out of a population
3. Selection (Natural
and Artificial)- different abilities of individuals to survive and
produce
offspring able to cope with a particular environment
4. Random Genetic
Drift- random changes in allele frequency that occur by chance.
Effects small pops much more than large ones.
Mutation- ultimate source
of variation, however, it is a weak force for changing allele
frequencies
-most mutations harmful
to organism
-slow mutation rates argument for the earth’s age being 4.5 billion years.
How mutation rates effect allele frequencies:
pt = po (1 - u)t t = generations po = freq of dominant allele at a given time
pt = freq of dominant after t generations
u = rate of mutation
frequency of A decreases
gradually because a fraction of them changes every generation
to a
if p = 1 for A
(and if mutation rate is 1/100,000 or 10-5 per gene per generation) it
will take
~1000 generations to lower the frequency to .99
pt = 1(1 - 10-5)1000 or [1 X (.99999)1000]
the smaller the initial
frequency the longer time required (a change of .01 will take about
2000 generations if
initial frequency is .5)
Gene Flow (migration)- genetic migration,
individuals moving from one to another population
and interbreed with
its members.
-may not change gene frequency for whole species but it can change it locally.
Genetic Drift:
-pop not infinitely large, there are finite
-breeding individuals produce virtually infinite # of gamete combos from
gene pool
-because of pop size only a few gametes will participate in fertilization
Therefore, from generation to generation we can expect different combos
rather
than repeat the same ones ("One in a Million", "there will never
be another quite
like you")
Genetic drift will contribute to fixation of alleles
Ex. if T and t are in a population how long could it take for t to
be eliminated? (in
other words, how long before p = 1.0 and q = 0?)
Rate of fixation = 1/2N N = # of individuals in population
**This will determine how many genes an individual has will be fixed with
a single allele
each generation
**The smaller the population the greater the fixation rate.
Rate of fixation if 2 individuals:
1/2(2) = 1/4 in a monohybrid cross, how many individuals will be
expected to be
homozygous dominant?
If N = 30
1/2(30) = 1/60 or .017 this # indicates that .017 or 1.7% of alleles would
be
expected to fix each generation
if in humans with 100,000 genes then (.017)(100,000)
equals 1700 alleles will fix
every generation for 30 individuals
if N = 90
1/2(90) = 1/180 or .006 then (.006)(100,000) = 600 alleles will fix per generation
if N = 90,000
1/2(90,000) = 1/180,000 or .0000055 (5.5 X 10-6)
then (.0000055)(100,000) = .55 alleles will fix per generation (or in 2
generations
one will fix)