DNA and amino acid sequence evolution Flashcards
What was the major school of thought about driving forces in evolution in the 1930s?
Synthesis of natural selection (Darwin) and genetics (Mendel)
What were the 2 schools of thought about the driving forces in evolution from the 1930s to the 1960s?
A- little genetic variation within species
B- lots of genetic variation within species
What school of thought was proven right in the mid-1960s and how were they proven right?
School B using protein electrophoresis
What is the major question about genetic diversity now?
What controls high levels of genetic diversity?
What are the 2 schools of thought now about the importance of random genetic drift and natural selection?
Selectionists believe that gene substitutions occur as a result of positive selection whereby an allele predominates only if it improves fitness
Neutralists believe most of the variation within and between species, is due to random genetic drift of mutant alleles that are selectively neutral
What do selectionists give as strong evidence for balancing selection?
Sickle-cell anaemia as it is caused by a single nucleotide polymorphism in the β-globulin gene and results in clumped haemoglobin and red blood cells that become sickle-shaped under oxygen stress
It actually increases life-expectancy where malaria is present so the balancing selection promotes the polymorphism even though it is not advantageous anywhere else
How can you test for neutral theory?
Look for differences in the ratios between synonymous and non-synonymous mutations between species that are either polymorphic or invariant within each of the 2 species
What would neutral theory predict about the ratios between synonymous and non-synonymous mutations?
They would be the same as fixation or elimination is viewed as the end result of genetic drift
