There are five main factors that can affect the Hardy-Weinberg principle. These factors include:

1. Genetic drift:
Genetic drift refers to the random changes in the frequency of alleles in a population. It is particularly significant in small populations where chance events can have a greater impact. Genetic drift can lead to changes in the allele frequencies over time, which can deviate from the expected proportions predicted by the Hardy-Weinberg principle.

2. Gene flow:
Gene flow occurs when individuals migrate between populations and bring new alleles with them. This can introduce new genetic variation into a population and can potentially alter the allele frequencies. Gene flow can disrupt the equilibrium predicted by the Hardy-Weinberg principle.

3. Mutation:
Mutations are random changes in the DNA sequence that can create new alleles. These new alleles can affect the allele frequencies in a population and can lead to deviations from the Hardy-Weinberg equilibrium.

4. Non-random mating:
The Hardy-Weinberg principle assumes random mating within a population, meaning that individuals choose their mates without regard to their genotypes. However, in reality, individuals often choose mates based on certain traits or characteristics, which can lead to non-random mating. Non-random mating can lead to changes in the genotype frequencies and can violate the assumptions of the Hardy-Weinberg principle.

5. Natural selection:
Natural selection is the process by which certain traits become more or less common in a population over time. If certain alleles provide a selective advantage, they will increase in frequency, while alleles with a disadvantage will decrease. Natural selection can cause changes in the allele frequencies and can lead to deviations from the Hardy-Weinberg equilibrium.

In conclusion, the Hardy-Weinberg principle can be affected by five main factors: genetic drift, gene flow, mutation, non-random mating, and natural selection. These factors can lead to changes in the genotype and allele frequencies in a population, which can deviate from the expected proportions predicted by the Hardy-Weinberg equilibrium.