IB DP Biology: HL复习笔记10.3.1 Gene Pools

• A gene pool consists of all the genes and their different alleles, present in an interbreeding population
• Some populations of the same species are geographically isolated from each other
  • So multiple gene pools can exist for a species
•  Individuals in a population tend to have common characteristics and resemble each other
  • Two geographically-isolated population may have different characteristics whilst still being the same species
  • This is one basis for speciation
•  A consideration of all the genes (and alleles thereof) in a population is important as that will govern the genomes of the next generation
  • This collection of genes and alleles is commonly called the gene pool

Calculating allele frequencies

• Allele frequencies are defined as the relative abundance of alleles for a particular gene
• Allele frequency is calculated by dividing the number of times the allele of interest is observed in a population by the total number of copies of all the alleles at that particular genetic locus in the population
  • Allele frequencies are expressed as a number between 0.0 and 1.0 or as percentages 0 - 100%
    • We can think of this as a probability that an allele chosen at random in a given gene will be a particular allele of interest
  •  The frequencies of all the alleles for a particular gene must add up to 1

   Step 1: Calculate the sum of the allele frequencies given

   Step 2: Work out the sum of the remaining allele frequencies

   Step 3: Apply the 4:1 ratio of albino allele: Himalayan allele given in the question

   Step 4: Complete the table with these frequencies

Stable gene pools

• Populations retain a stable gene pool under the following conditions
  • The population is large
  • Each individual in the population has an equal chance of mating
  • That matings are random
  • There are no selective pressures acting upon individuals based on their phenotype
•  A stable gene pool means that a population is not evolving