Final Exam Flashcards
Discrete Variation
Traits determined by a single gene. Widow’s peak, cystic fibrosis, etc.
Quantitative Variation
Traits influenced by multiple genes and also environmental factors. Height, skin colour, etc.
Hardy-Weinberg Equation/Genotypic Frequencies
p2 + 2pq + q2 = 1
Where ‘p2‘ represents the frequency of the homozygous dominant genotype (AA), ‘2pq‘ the frequency of the heterozygous genotype (Aa) and ‘q2‘ the frequency of the homozygous recessive genotype (aa). The sum of these three genotypes must equal 1 (100%).
p + q = 1 concerns estimating the frequency of alleles in a population. The combined frequency of both the alleles must equal 1 therefore, if the frequency of one allele is known, it is possible to calculate the frequency of the other allele simply by rearranging the equation.
Heterozygosity
The measure of genetic variation at one single locus (2pq). This does not represent genetic diversity so you must use the average heterozygosity.
Allelic Diversity
They average number of allele per locus. The higher allelic diversity and heterozygosity means the species is more common.
Hardy Weinberg Assumptions
No natural selection: There are no evolutionary pressures which may favour a particular allele.
Random mating: Each individual in a population mates randomly so that mating with an individual carrying a particular allele is not favoured.
No mutations: There are no DNA mutations occurring for the alleles which may affect their function.
A closed population: Individuals within the population do not leave and new individuals are not introduced to the population.
Large population size: The population is considered large enough, at best infinite, so that major changes in allele frequencies do not cause a genetic drift.
Micro Evolution
Refers to small-scale changes in the genetic composition of a population over a relatively short period of time. Occur within a species and do not lead to the formation of new species (which would be macroevolution). Instead, microevolution results in variations in traits (coloration, size, resistance to environmental pressures, etc.).
Mechanisms of Micro Evolution
Mutation – Random changes in DNA that introduce new genetic variations.
Natural Selection – Favorable traits become more common as they help organisms survive and reproduce.
Genetic Drift – Random fluctuations in allele frequencies, especially in small populations.
Gene Flow (Migration) – Movement of genes between populations through migration and reproduction.
Non-Random Mating – When individuals choose mates based on certain traits, influencing genetic variation.
Founders Effect
Occurs when a small group of individuals becomes isolated or separated from a larger population to form a new, isolated population. Leads to lower genetic diversity in the new population. Can result from natural disasters. The concept of establishing a population from a small group of founders.
Bottleneck Effect
Type of genetic drift that occurs when a population experiences a drastic reduction in size due to an environmental disaster, disease outbreak, human activity, or other factors. This sudden reduction leads to a loss of genetic diversity, as only a small number of individuals survive to pass on their genes.
