Lab Manual Ch. 4 Flashcards
Great Lakes fishery populations
- overexploitation and invasion by exotic species has placed severe stress on native fish species
- many commercially valuable species have been eliminated/reduced
what evolutionary forces have had a significant impact on the genetic variation of Great Lakes fishery populations?
- selection forces of humans reduce genetic diversity (eg size-selective fishing gear, habitat elimination, alteration of prey species, pollution stresses)
- gene flow; the greater the rate of gene flow, the more homogeneous two populations become. any activity which changes the population densities affects the distance between populations
- genetic drift
what did managers have to do to combat the Great Lakes problem?
- stock the lakes with fish that would eventually begin to reproduce and replenish species
- cultivated in hatcheries
issues with cultivating fish in hatcheries then releasing them into the wild
- genetic diversity is low
- locally adapted populations may be replaced with genetically homogeneous populations which limits adaptive potential
- may increase competition or introduce diseases
why are traditional Mendelian methods of making crosses/scoring phenotypes insufficient for a detailed estimate of genetic variation within a population?
- restricted primarily to phenotypic characters
- too time consuming to wait for future generations
- does not always yield precise information on genotype (homozygous dominant vs heterozygote)
- too many gene loci in most organisms for this process to yield reliable estimates of genetic variation
protein electrophoresis
- tissue sample homogenised to release enzymes
- drop of each sample placed in a straight row near the edge of a rectangular sheet of cellulose acetate gel
- electrodes attached to filter paper wicks soaked in buffer solution at the end of each gel
- electrical current applied across the gel for 20/30 mins
- gel stained for a particular enzyme by pouring over it a solution containing a substrate along with a dye that precipitates where the reaction occurs
- dark bands appear
why do different allonyms move through the gel at different rates?
enzymes of the same size and shape move at a rate determined largely by the ratio of positively charged to negatively charged amino acids
allozymes
differ in their amino acid sequence and are the product of a single genetic locus
diagram for allozyme gel analysis
monomeric enzyme
produces one polypeptide chain which is a fully functional protein
dimeric enzyme
single polypeptide chain is produced by each allele, but these remain inactive until they form dimers
it is necessary to screen at least —— enzyme loci to get a representative sample of the variation in populations
12 to 15
two measures of genetic variation
polymorphism (P)
heterozygosity (H)
variation as measured by the average heterozygosity represents
the adaptive potential of the species and is a powerful evolutionary mechanism
two statistics to quantify genetic differentiation between populations
- genetic identity, I, which estimates the proportion of genes that are identical in the two populations being compared
- genetic distance, D, which estimates the accumulated number of gene differences per locus that have occurred over evolutionary time
