3.4.8 - Genetic Variation Flashcards
Multiple allele definition?
More than 2 alleles, of which 2 may present at the loci of an individual’s homologous chromosomes
Example of co-dominance?
Snapdragon plant can have red pigment, or white
If the offspring have 1 of each allele, the flowers will appear pink
Example of multiple allele gene?
Blood types, A, O, B
Both A and B are co-dominant and O is recessive to both
Gene pool definition?
All the alleles of all genes of all individuals in a population at any given time
Allele frequency definition?
Number of times an allele occurs within the gene pool
Hardy Weinberg conditions?
No mutations arise
Isolated population (no flow of alleles in/ out)
No selection (all alleles equally likely to pass to next generation)
Population is large
Random mating
Hardy Weinberg equations?
p + q = 1
p^2 + 2pq + q^2 = 1
Where p^2 is the frequency of homologous dominant, 2pq is the frequency of carriers and q^2 is the frequency of homologous recessive
Selection definition?
Process by which organisms are better adapted to their environment survive and breed, while the less adapted fail to do so
Process which selection occurs?
Organisms produce more offspring than can be supported and population remains not stable (must be intraspecific competition)
Within gene pool, some alleles more likely to survive, obtain resources, grow rapidly and better chance of reproduction
Only those successful at reproduction can pass alleles to next generation
Example of selection?
Peppered moth: White used to favourable, industrial revolution came, buildings black with soot. Black moths therefore more likely to survive as they camouflage. The frequency of the black moths increase
Directional selection definition?
Selection may favour individuals that vary in 1 direction from the mean of the population
Directional selection fur length example?
At 10 degrees, mean optimum fur length = 15mm
Temperature falls to 5 degrees, long fur is more suited
Over generations, mean fur length increases, as they survive more
Over further generations, the shift in mean fur length continues, new optimum = 20mm
Stabilising selection definition?
When the environment remains constant, those with phenotype closest to the mean are more likely to pass alleles to the next generation
Tends to eliminate phenotypes at the extremes
Co-dominance definition?
Where both alleles are equally dominant, and broth expressed in the phenotype
