Complex Traits
What is a discrete trait? Give example (Q1)
Phenotypes fall into a few distinct classes
example: blood type
What is Heritability? (Q2)
The proportion of phenotypic variation in a population attributed to a genetic variation
Define natural selection (Q10)
Process where organisms better adapted to their environment survive and reproduce
Name one of the three types of selection (not positive or negative)
Directional, disruptive, or stabilizing (also credit for balancing)
What is a polygenic trait? Give example (Q1)
phenotypes display a (bell shaped) normal distribution
example: height
How do you measure Heritability? (Q3)
Test different genotypes in the same environment and observe phenotypic variation between generations
What is fitness?
The number of surviving, fertile offspring that an individual produces
Explain disruptive selection
When phenotypic distribution is pushed to two seperate extremes
What is pleiotropy?
When a single gene has multiple effects.
example: marfan syndrome is one mutant allele, but impacts many systems such as vision and cardiovascular function.
What would the resulting heritability be for an experiment using the same genotype in different environments?
(give answer as a percentage)
0%
What is the difference between positive and negative selection?
Positive selection=Selection that increases the frequency of an allele
Negative Selection=Selection that decreases frequency of an allele
What type of selection would be used to describe mice developing a darker fur color
When doing a cross with a polygenic trait, during which generation would you see the continuum of phenotypes?
F2 generation
What is the maximum heritability? Explain what this would mean
(Answer given as a number)
Maximum heritability=1
100% of phenotypic variation in a population can be attributed to genetic variation
Which type of selection (positive or negative) would be more common in the wild? Why?
Negative because most new mutations are neutral or harmful
Is artificial selection generally
a) Directional
b) Disruptive
c) Stabilizing
a) Directional
Would the mendelian pea pod experiment be an example of polygenic inheritance? Why or why not
No, this is discrete because inheritance is influenced by single genes
Based on your knowledge of heritability, is height likely to have a heritability of >.5, <.5, or neither?
Explain your answer for full credit
>.5
Environmental factors will not play as much of a role on height as genetics will (tall genes will likely result in a tall person)
How do you calculate relative fitness?
# of offspring of a certain genotype/# of offspring of a different genotype (with higher fitness)
Explain a situation where a heterozygote advantage may occur (or has occurred)
Carriers of sickle cell anemia are more resistant to malaria