Population genetics Flashcards
What are uses of population genetics?
• Forensic genetics
o Paternity testing
o Crime scenes
• Conservation genetics
• Management of pesticide and antibiotic resistance
o Natural selection resulting
• Origins of people and populations of animals
Why is conservation genetics important?
• Design of captive breeding programs so that genetic variability is maintained
• Mating structures in endangered populations
o Minimum viable population size maintenance-
50 for a captive population
500 for a wild population
• Resolving taxonomic uncertainties
• Source populations for recovery programs
• Paternity testing and forensics
What is a polymorphism?
• Polymorphism- existence of two or more allelic forms
What is monomorphic?
• Monomorphic- only one allelic form
What is an allozyme?
• Allozyme- variations in form of a metabolic enzyme
What is vertebrate allozyme polymorphic loci percentage?
15-30%
What is invertebrate allozyme polymorphic
30-40%
What is a plant allozyme polymorphic loci percentage?
25%
What is vertebrate heterozygosity percentage?
5-8%
What is invertebrate heterozygosity percentage?
7-15%
What is plant heterozygosity percentage?
7%
How does evolution proceed?
• Evolution proceeds by the differential reproduction of genotypes
How does selection and variation interact?
• Expect variation to be eliminated by selection
What is the interaction between selection and evolution?
• Selection is pushing populations in one direction, while evolutionary forces are pushing populations in another direction to maintain variability
Why do lethal alleles still exist in a population?
• Natural selection can be weak if lethal allele kills you after reproductive age, hence why deleterious alleles are maintained in the population
Where does new genetic variation come from?
- Mutation
- Migration
- Sexual reproduction
How does mutation introduce new genetic variation?
o Original variation from mutation
o Slow process
o pn=p0e^(-nu)
Let the mutation rate from allele a to allele A be u
pn is the frequency of allele A at time n
p0 is the frequency of allele A at time 0
How fast are mutation rates?
o Mutation rates are:
Very slow- do not contribute much to genetic variability but is root of all genetic variability
How do sexual species generate variability?
o Sex generates variability
Sexual species
• Crosssing over and sexual reproduction produces high heterozygosity and shuffling of exons
• Genetically variable
How do asexual species generate variability?
Asexual/clonal species
• Variation arises only through mutation
• Amount of variation and the rate of evolution is lower in asexual species
• Asexual species are very similar to each other
What can gene duplication result in?
- Natural selection can only act on existing DNA sequences
* Gene duplication can allow for new gene function and permits evolutionary change
What can duplicated/repeated sequences resulting from gene duplication be?
• Duplicated/ repeated sequences can:
o Retain original function
o Acquire new functions
o Lose function in some duplicates
What are pseudogenes?
• Pseudogenes-segments of DNA that are related to real genes. Pseudogenes have lost at least some functionality, relative to the complete gene, in cellular gene expression or protein-coding ability
What are gene families, when are they switched on and where do they come from?
o May cooperate to produce gene products
o Various versions switched on in different tissues and different lifestages