Topic 1: Intro to Population Genetics Flashcards
What is the field of population genetics?
The field of biology that studies the genetic composition of biological populations, and the changes in genetic composition that result from various influences
What are the three fields that fall into population genetics?
Theoretical pop gen: uses math and computer models to understand the effects of different processes
Experimental pop gen: uses controlled lab and field experiments to test theoretical predictions
Empirical pop gen: studies genetic variation in natural populations often with the aim of understanding population genetics
What are the two other factors that population genetics is intimately bound with?
Evolution which can be defined as any change in a population’s genetic composition, and natural selection which can lead to evolution.
It is often regarded as the theoretical cornerstone of evolutionary biology
What are the four processes that lead to changes in gene frequency?
Genetic drift, mutations, migration, natural selection
What was Darwin’s contribution to population genetics?
He published the Origin of Species in 1859
It contained 2 main theses:
1. Modern species were descended from common ancestors
2. The process of natural selection was the major mechanism of evolutionary change
Proposed the 4 conditions that must be met for natural selection to happen:
1. More individuals are born than survive
2. Individuals vary
3. Some variation is inherited
4. Survival and reproduction are not random
Why was the second thesis from the Origin of Species not readily accepted? (the process of natural selection was the major mechanism of evolutionary change)
Darwin did not propose a mechanism of inheritance, , and many thought that inheritance was still blending, and if evolution was caused by selection on variation, and variation is inherited by blending, why does variation exist on populations?
What are the two schools of thought that were present in the 19th century?
Gradualists: believed that selection acts on small individual variations and therefore evolution is slow and gradual (people who study continuous variation think this)
Saltationist: believed that natural selection must act on large discontinuous traits therefore evolution is mostly stasis with occasional jumps (punctuated equilibrium)
What was the reaction from gradualists and saltationists when Mendel’s work was rediscovered and it was revealed that inheritance was due to the passing on of discrete units?
Saltationists were happy as they believed that this supported their view of evolution by discrete steps (Mendelians)
Gradualists were unhappy as they felt that this was inconsistent with their observations of continuous traits and the process of gradual evolution (biometricians)
What was the major discovery of Hardy and Weinberg?
They showed that allele frequencies and genotype frequencies will remain constant in the absence of other factors (basis for theoretical population genetics)
What was the contribution of R.A Fisher to genetics?
He showed that variation in quantitative characters could be explained by Mendelian inheritance, and developed stats techniques and developed quantitative genetics.
Wrote “Genetic Theory of Natural Selection”
What was the contribution of JBS Haldane to population genetics?
Developed the mathematical theory of natural selection and pioneered mathematical predictions of the changes in gene frequency due to selection.
“Causes of Evolution”
What was the contributions of Sewell Wright to the field of population genetic?
Known for his work on inbreeding and effective population size, he emphasized evolution through genetic drift in small populations
Shifting balance theory: theory describes evolution as a process by which favourable gene combinations come together in small isolated populations then increase in frequency by selection
What was the contribution of Dobzhansky to population genetics?
He used empirical data from natural and experimental Drosophila to support the theoretical work of Fisher, Wright and Haldane.
“Genetics and the Origin of species” argued that mutation is the source of all variation, and initiated the modern synthesis of evolutionary biology and genetics
What was the contribution of Lewontin and Hubby to population genetics?
The published the technique of protein electrophoresis, and found more genetic variation in natural population. Pioneers of molecular genetics
What was the contribution of Kimura to population genetics?
Founded the neutral theory of molecular evolution, which proposed that most variation at the protein level is neutral and variation is maintained by a balance of mutation and genetic drift
This was a controversial idea leading to selectionist versus neutralist
