AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |
Back to Blog
There are numerous examples of pleiotropy in humans. Some genes affect more than one phenotypic trait. There are genes for straight and curly hair, and if an individual is heterozygous, they will typically have the phenotype of wavy hair. Most individuals with Tay Sachs disease die at a young age, typically by the age of five years.įigure 5.14.3 Three phenotypes of hair through the incomplete dominance model.Īnother good example of incomplete dominance in humans is hair type. This leads to the accumulation of lipids in the brain starting in utero, which causes significant brain damage. Homozygotes who have only defective allele, however, produce only nonfunctional enzyme. Heterozygotes who have one normal and one defective allele produce half as much functional enzyme as the normal homozygote, and this is enough for normal development. A defective allele for the gene results in the production of a nonfunctional enzyme. The normal allele for the gene in this case produces an enzyme that is responsible for breaking down lipids. As a result, the heterozygote individual produces only half the amount of normal protein as is produced by an individual who is homozygous for the normal allele.Īn example of incomplete dominance in humans is Tay Sachs disease. Generally, this happens when the two alleles for a given gene both produce proteins, but one protein is not functional. In this case, an intermediate phenotype results in heterozygotes who inherit both alleles. No antigen is associated with the O allele, so people with the OO genotype have no antigens for ABO blood type in their blood (type O blood).Īnother relationship that may occur between alleles for the same gene is incomplete dominance. This occurs when the dominant allele is not completely dominant. Similarly, both BB and BO genotypes have the same phenotype, with the B antigen in their blood (type B blood). As a result, both AA and AO genotypes have the same phenotype, with the A antigen in their blood (type A blood). The A and B alleles are dominant to the O allele. There are three common alleles for this trait, which are represented by the letters A, B, and O.Īs shown in the table there are six possible ABO genotypes, because the three alleles, taken two at a time, result in six possible combinations. Your blood type refers to which of certain proteins called antigens are found on your red blood cells. Traits controlled by a single gene with more than two alleles are called multiple allele traits. The majority of human genes are thought to have more than two normal versions, or alleles. Figure 5.14.2 ABO blood types per genotype.
0 Comments
Read More
Leave a Reply. |