Dominant-recessive interactions

The dominant-recessive interactions of allelic genes, gene complementation, epistasis, and the modification an interactions of nonallelic genes have been the object of investigations in genetics for a long time. 

In some cases the gene modifiers could, apparently, change the dominant-recessive interaction between isozymes (which is regularly of a codominant character). For instance, a gene modifier was found in D. melanogaster which controlled the dominant expression of the slow isozyme of alkaline phosphatase in heterozygous flies. In the F2 a segregation was obtained wherein the ratio of individuals with slow and fast isozymes was equal to 3 1 (Schneiderman et al., 1966). 

A major reason for using merodiploids is to study the interaction between different alleles of the same gene. This often tells us a great deal about how a gene or the gene product functions. The two simplest types of interactions are dominant and recessive. A cell that is z+/Fz behaves like a z+ cell as far as the metabolism of j8-galactosidase is concerned. Therefore, the z+ allele is dominant to the z allele, or conversely, the z allele is recessive to the z+ allele. 

Alleles are classified by how they interact with each other. The red-hair allele is recessive —i.e., one such gene on each member of the chromosome pair is required for the trait to be manifest. The nonred-hair allele, in contrast, is dominant —i.e., a person with either one or two of these genes has nonred hair. It is customary to designate dominant alleles with capital letters and recessive alleles with lower-case letters. If r stands for the red-hair gene and R for its alternative, rr persons will have red hair, and Rr and RR will not. 

It was shown81 that for a wide variety of gene interactions the mutation component is 1 for a detrimental trait determined solely by balance between mutation and selection. If the trait has a quantitative basis, the principle still holds true. For example, if the disease is expressed only when a particular threshold of the underlying variable is exceeded, the mutation component is still 1. The dominance of the gene also does not matter even a rare recessive disease has a mutation component of 1. 

Type 2 von Willebrand disease, diagnosed in 9% to 30% of affected patients, is characterized by a qualitative abnormality of von Willebrand factor. Bleeding manifestations may be more severe than with type 1 disease. Inheritance is most often autosomal dominant, but may be recessive. Type 2 von Willebrand disease may be further subdivided into four variants. Type 2A is the most frequent subtype and is characterized by a reduced von Willebrand factor-platelet interaction and an absence of high- and intermediate-molecular-weight factor multimers. Type 2B is a less common variant in which there is an abnormal von Willebrand factor that has an increased affinity for the platelet glycoprotein Ib receptor. This is associated with thrombocytopenia, which is usually mild. In addition, there are usually no high-molecular-weight forms of von Willebrand factor. Type 2M... 

Zeolites exhibit many unique adsorption properties, mainly because of then-unique surface chemistry. The surface of the framework is essentially oxygen atoms, whereas Si and A1 are buried or recessed in the tetrahedra of oxygen atoms. They therefore are not fully exposed and cannot be readily accessed by adsorbate molecules. Also, the anionic oxygen atoms are more abundant and are much more polarizable than the A1 and Si cations. Therefore, the numerous anionic oxygen atoms dominate the van der Waals interactions with the sorbate molecules, that is, the 4>d + [Pg.173]

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