Week 13
define population genetics, population, and gene pool
population: a group of interbreeding individuals that have a common set of genes and exist in the same place and time
population genetics: study of the genetic makeup of a pop. and the changes in its genetic composition over time
gene pool: the common set of genes in a population
How does migration affect genetic variation in and between populations?
The source population will lose genetic variation
The recipient population will gain genetic variation
The two populations will become more genetically similar
true/false: Chromosomal rearrangments can cause lead to cancer
true
If a trait has a high additive genetic variation in proportion to total variance, what does this tell us about how it will respond to selection?
It will respond well to selection becuase it has a high narrow sense heritability
What are the 5 assumptions of Hardy-Weinberg Equlilibrium?
1. No new mutations
2. No migration
3. Large pop.
4. Random mating
5. No natural selection (same fitness)
What is the effect of inbreeding on genotypic frequencies?
increase in homozygosity
decrease in heterozygosity
What was the goal of the human genome project?
generate the first sequence of the human genome
In many species, as body size increases, litter size also increases. How would you describe this phenomeon?
positive correlation
Based on the table below, calculate allelic, genotypic, and expected genotypic ratios (if it were in Hardy-Weinberg EQ)
AA = 34
Aa = 44
aa = 22
f(AA)= 0.34 p= 0.56 Expected: f(AA) = 0.31
f(Aa)=0.44 q= 0.44 f(Aa) = 0.49
f(aa)= 0.22 f(aa) = 0.19
In a population of rats, grey fur is the wildtype to the brown fur mutation. Out of the 204 rats, 38 have brown fur. If the forward mutation rate is 4x10^-5 and the reverse mutation rate is 1x10^-5. What is the expected change delta q?
p=0.57
q=0.43
delta q = 1.8 x 10^-5
true/false: it only takes one mutation to become cancerous
false; usually 3-9 mutations are needed
In white-throated sparrows, about 98% of the observed pairings are between a mate with white-stripes and another with tan stripes. What phenomeon is being observed?
negative assortative mating
A rancher determines that the average amount of wool produced by sheep in her flock is 10 kg per year. In an attempt to increase the wool production in the flock, she picks 10 sheep with the highest wool production; the average amount of wool produced per sheep by those selected is 32kg per year. She interbred these selected sheep and found that the average wool production among the progeny of the selected sheep was 24 kg per sheep per year. What is the narrow sense heritability of wool production?
S= 22
R=14
narrow sense heritability= 0.64
In a population of frogs, spots are dominant to no spots. 16% of frogs in this population do not have spots. If there is an inbreeding coefficient in this population of 0.3, what would you expect to be the new frequency of frogs with no spots in the next generation?
0.232
What is the difference between a tumor suppressor gene vs. an oncogene
tumor suppressor gene: inhibits cell division; needs two mutated copies to remove inhibition
oncogene: stimulates cell division; only needs one mutated copy to over-stimulate cell division
Overhunting of northern elephant seals in the 1890s reduced their population to roughly 20 individuals. What type of evolutary event is this?
Genetic bottleneck (genetic drift)
A farmer wants to increase the size of strawberries on his farm. Strawberries have a narrow sense heritability of 55% for weight. The mean weight of the strawberries on his farm is 11g. If strawberries with a mean weight of 15g are intercrossed, what is the mean strawberry weight for the next generation?
13.2 g
Calculate fitness and selection coefficient for the following genotypes :
AA 15
Aa 32
aa 3
AA: w=0.47 s=0.53
Aa: w=1 s=0
aa: w=0.09 s=0.91
A breast cancer cell travels through the lymph nodes into the lungs. Is this a benign or malignant tumor? Why?
Malignant; it is spreading to other parts of the body
What is the main source of genetic variation in a population?
mutations