Define Genetic Variation
The differences in nucleotide sequence within a population
variation and discrete characteristics
Variation can be discrete of quantitive(continuous)
-one character or other NO in between
trait=single gene
i.e mendel
Discrete Variation: Polymorphism
Occurence of different forms –> among members of a population
2+ Phenotypes in same population
i.e hawk with 2 morphs
Define quantitive characteristics
continuous variation (Height and weight) --> Histograms and statistics
How do you measure genetic variation?
Average Heterozygosity
-Nucleotide variability: Compares DNA sequences in individuals in a population
I.E (Humans vs. humans or Human vs.Fly)
Define geographic variation
Variation through space and time( spatial axis)
i.e some mice isolated by mountains–> 2 different populations
What are Sources of genetic variation?
- Random- random changes in DNA sequence (deletion, duplication, transfer)
- Directed- organisms evolve to generate variation(independent assortment, crossing over)
- Point Mutations- Change in one base of a gene (sickle cell anemia)
- Change gene number or position- chromosomes can fuse/split, duplicate gene gets new function
- Gene duplication- Increases genome size= more material for evolution
- Rapid reproduction- High genetic variation
- Sexual reprocduction- multicellular eukaryotes incorporate changes into germ line. Rearranges alleles to new combos
- Horizontal Gene transfer- Transfer of genes from one organism to another other reproduction
Genetic Transmissions
- Vertical: Parent to offspring
2. Horizontal: One organism –> another organism
Preservation of Genetic Variation
- Neutral Variation: Doesn’t confer advantages/ disadvantages
- Ploidy: Various copies of gene
- Balancing selection: Natural selection maintains stable frequency of 2+ populations
- Heterozygote= increase in fitness
- Frequency decreases if too common
