Multiple Alleles
Not all genetic traits are composed of only two alleles. Some genes have more alleles, also called multiple alleles. An example would be the human blood type.
There is allele A, B, and O. The alleles may share codominance and are expressed equally such as in the case of type AB. Or there is a dominance of allele type over the other. For example, a genotype of AO results in a phenotype of A.
There is allele A, B, and O. The alleles may share codominance and are expressed equally such as in the case of type AB. Or there is a dominance of allele type over the other. For example, a genotype of AO results in a phenotype of A.
Codominance vs. Incomplete Dominance
Codominance: Alleles expressed equally in the phenotype.
Example: One black chicken mixed with one white chicken would result in a chicken with both black and white feathers.
Incomplete Dominance: Alleles blend in the phenotype.
Example: One black chicken mixed with one white chicken would create grey offspring
Example: One black chicken mixed with one white chicken would result in a chicken with both black and white feathers.
Incomplete Dominance: Alleles blend in the phenotype.
Example: One black chicken mixed with one white chicken would create grey offspring
Polygenic Inheritance
Polygenic inheritance is a single characteristic that is controlled by more than one gene, like human skin color and height.
Variation follows a bell shape distribution, ie not many people at the extreme ends of a trait.
Variation follows a bell shape distribution, ie not many people at the extreme ends of a trait.
Pedigrees
Pedigrees are charts of the genetic history of a family over a course of several generations. Squares are men, circles are women. A line between a circle and a male signifies marriage and a line and a square/circle resulting from the marriage line signifies offspring.
Pedigrees can be used to determine whether or not someone was a heterozygous.
Pedigrees can be used to determine whether or not someone was a heterozygous.
The Genetic Code is Nearly Universal
Nearly every organism shares the same codons for the same amino acids. This also provides evidence of evolution since this shows how all organisms are related in a way.