Codominance

Trait: Human blood type

How it fits into the category: Codominance is a type of inheritance in which both alleles of a gene are expressed equally. In the case of human blood type, the A and B alleles are codominant. This means that if an individual has one A allele and one B allele, they will have blood type AB.

How often the trait is seen among living organisms: Codominance is a relatively common form of inheritance. It is seen in many different organisms, including humans, animals, and plants.

Chromosomal location: The ABO blood group gene is located on chromosome 9.

Alleles: There are three alleles of the ABO blood group gene: A, B, and O.

Mixture of alleles: Individuals with blood type AB have one A allele and one B allele.

Incomplete Dominance

Trait: Snapdragon flower color

How it fits into the category: Incomplete dominance is a type of inheritance in which the phenotype of an individual is a blend of the phenotypes of the two parents. In the case of snapdragon flower color, the red and white alleles are incompletely dominant. This means that if an individual has one red allele and one white allele, they will have pink flowers.

How often the trait is seen among living organisms: Incomplete dominance is a relatively common form of inheritance. It is seen in many different organisms, including humans, animals, and plants.

Chromosomal location: The snapdragon flower color gene is located on chromosome 17.

Alleles: There are two alleles of the snapdragon flower color gene: red and white.

Mixture of alleles: Individuals with pink flowers have one red allele and one white allele.

Multiple Alleles

Trait: Human eye color

How it fits into the category: Multiple alleles is a type of inheritance in which there are more than two alleles for a particular gene. In the case of human eye color, there are two main genes that contribute to eye color: the OCA2 gene and the HERC2 gene. Each of these genes has multiple alleles. For example, the OCA2 gene has over 10 different alleles.

How often the trait is seen among living organisms: Multiple alleles is a relatively common form of inheritance. It is seen in many different organisms, including humans, animals, and plants.

Chromosomal location: The OCA2 gene is located on chromosome 15 and the HERC2 gene is located on chromosome 5.

Alleles: There are over 10 different alleles of the OCA2 gene and over 10 different alleles of the HERC2 gene.

Mixture of alleles: The specific alleles that an individual has for the OCA2 and HERC2 genes will determine their eye color. For example, individuals with two copies of the brown allele of the OCA2 gene will have brown eyes. Individuals with two copies of the blue allele of the OCA2 gene will have blue eyes. Individuals with one copy of the brown allele and one copy of the blue allele will have hazel eyes.

Sex-Linked

Trait: Colorblindness

How it fits into the category: Sex-linked inheritance is a type of inheritance in which a gene is located on the X or Y chromosome. In the case of colorblindness, the gene for color vision is located on the X chromosome. This means that males are more likely to be colorblind than females.

How often the trait is seen among living organisms: Sex-linked inheritance is a relatively common form of inheritance. It is seen in many different organisms, including humans, animals, and plants.

Chromosomal location: The gene for color vision is located on the X chromosome.

Alleles: There are two main alleles of the gene for color vision: normal and colorblind.

Mixture of alleles: Males with one copy of the colorblind allele will be colorblind. Females with two copies of the colorblind allele will be colorblind. Females with one copy of the colorblind allele and one copy of the normal allele will be carriers of colorblindness.

Recessive Lethal

Trait: Tay-Sachs disease

How it fits into the category: Recessive lethal inheritance is a type of inheritance in which individuals who have two copies of the recessive allele for a particular gene will die at a young age. In the case of Tay-Sachs disease, the gene that encodes the enzyme hexosaminidase A is located on chromosome 15. Individuals who have two copies of the recessive allele for this gene will not produce enough hexosaminidase A, which will lead to the accumulation of a