Incomplete dominance is the situation in which one allele is not completely dominant over another allele. So for example spotted animals the are a base color with spots of another color with in the fur.
Codominance is the situation in which the phenotypes produced by both alleles are completely expressed. This is also like incomplete dominance with showing different colors in the fur.
Multiple alleles are a gene that has more than two alleles. Like the color of the fur is 2 to 3 different colors.
Polygenic trait is a trait controlled by two or more genes.
Environmental conditions can determine a animals genes and in what way they are expressed. They can also determine genetics traits internally.
Created with images by Brian J Kelly - "Spice (A1300145)" • Violette79 - "Our Pretty Spots :))" • kmo - "Let us not forget the queen of the house...looking fully derpy today. #morevalla #dogs" • qmnonic - "MY corn" • skeeze - "dalmatian dog head" • Russellbande - "jack russell terrier jrt jack russell" • PublicDomainPictures - "africa african animal" • Sam Foles - "Ready to Pounce" • Pitsch - "cat animal white" • Dai Luo - "Spots"