Download Key terms: Classical school Balance school Genetic load Gel

BIOL 3046: Molecular evolution
Review material
Intro & Genetic load (Neutral_T1)
Key terms:
Classical school
Balance school
Genetic load
Gel electrophoresis
Selective death
Haldane’s dilemma
Mutational load
Substitutional load
Segregational load
Reproductive excess
Cost of selection
Hard selection
Soft selection
Incompatibility load
Lag load
Positive Darwinian Selection
Negative Darwinian selection
Review questions:
1. Compare the similarities and differences between the Balance and
Classical schools of Neo-Darwinism.
2. Although the predictions for natural variation under the balance school
were correct, their mechanism for the maintenance of such variation is
now believed to be wrong. Discuss why the predictions of balance
school were qualitatively correct, yet the mechanism was
unsatisfactory. [Part of the answer requires material from T2]
3. What is the genetic load on a population that has a mean fitness of
0.95? How much genetic death occurs in a population of 100000 per
generation?
4. Discuss the notion of genetic load as it relates to an entire population.
5. What is the relationship of hard and soft selection to arguments
against selectively maintained polymorphism based on the notion of
genetic load?
6. Why is mutational load approximately independent of the selective
coefficient of the new mutation? What are the implications for
mutational load as a source of load on populations? Note that our
model assumes that the alleles are recessive. What if they were
dominant? What if there were very many site that could experience
deleterious mutations?
7. Consider two populations. Populaiton1 has no reproductive excess,
whereas the Populaiton2 has an excess of 0.1. What are the relative
effects of natural selection on the size of populations 1 and 2 when the
cost of selection is 0.05? What about a cost of 0.15? What about the
rate of change, per generation? What do you need to known to be
able to predict the ultimate fate of the population?