Heritability Flashcards
How do environmental effects act on traits like height?
the same genotype can produce different phenotypes depending on what environment it is grown in
How does heritability affect monozygotic and dizygotic traits?
High heritability
- genetically identical individuals have identical phenotypes
- Genetically similar individuals have similar phenotypes
Low heritability
- individuals have different phenotypes, even when genetically similar or even identical
What is the equation of broad-sense heritability? H(N)
H(B) = V(G)/V(P)
G - genotypic
P - phenotypic
What happens to variation if there is no genetic variability?
No environmental effects?
If there are both genetic and environmental effects?
No genetic
- variation is completely environmental
- parents uncorrelated with offspring, unless parents live in similar environments to offspring
No environmental
- All variance is genetic
- offspring the same as their parents even when living in different environments
Both
- Heritability is between zero and one
- offspring resemble their parents but not exactly
How do you calculate Selection (S)? Response to selection (R)?
The average of the next population?
Survivors minus total pop.
Heritability times S
Old pop average plus R
What are broad sense and narrow sense heritability?
Broad - proportion of phenotypic variance that is due to genetic effects
- In a given POPULATION
Narrow - proportion of phenotypic variance that is due to additive genetic effects
- Between parents and offspring
What are the complications in measuring real-world complications? How do you correct it?
Parents and offspring share genes
Parents and offspring often share environment as well
So if offspring resemble parents, is it because of genes or environment? By randomizing genotypes across environments
How is heritability effected?
If you change the population or environment, you change the heritability
Traits can have a high heritability but be influenced by a new environment
If a genotype of the same species produces unfavourable results in a different environment, what is the easiest way to improve result?
Mimic the environment of the other genotype
What are size-number trade offs? Life history trade offs?
Flower example - larger flowers is favourable but means fewer flowers, so selection for size would be opposed by selection for more flowers
Life history is a pattern of allocation of time and energy to various basic activities
What is the comparison made in life history trade offs? Is it optimal? Why or why not?
Survivorship of progeny vs clutch size
It is close at times, but not optimal. Numbers aren’t all that matters as quality (fitness) is most important
How do you measure optimality in trade offs?
Multiply number of offspring by fitness of offspring (survivorship)
