Genes classical

Structure—function relationships of prolactin among a variety of species have been pubUshed (17,18). Only one gene for prolactin appears to exist (19). Although classically placed in the category of simple protein hormones, prolactin can be glycosylated. Carbohydrate attachment occurs at Asn-31, where the consensus glycosylation sequence Asn—X—Ser is found. 

The majority of industrial research describes classical approaches to yield improvement (49). However, there has been some work using genetically modified organisms. In the case of these recombinant organisms, the carotenoid biosynthetic gene cluster has been expressed in noncarotegenic species such as E. coli (50) and S. cerevisiae (51). 

The classic zinc fingers, the DNA-binding properties of which are discussed in Chapter 10, are small compact domains of about 30 residues that fold into an antiparallel p hairpin followed by an a helix. All known classic zinc fingers have a zinc atom bound to two cysteines in the hairpin and two histidines in the helix, creating a sequence motif common to all zinc finger genes. In the absence of zinc the structure is unfolded. 

A scientific procedure that turns the classical pharmacology approach upside down. Instead of finding the elusive receptor for a known hormone or transmitter what classical pharmacology aims at, reverse pharmacology is initiated through the discovery of the receptor gene and aspires to the identification of the receptors unknown ligand. 

Figure 2 The classical activation pathway of SHR. SHRs (gray circle) are associated with chaperones (rectangles). After binding of steroid hormones (black circle) SHRs activate target genes in the nucleus. Additional regulation mechanisms, e.g., phosphorylation are described in the text.

Classical global knockouts may have a developmental or lethal phenotype and thus preclude the analysis of the phenotypic consequences of the lack of a gene in specific tissues in adult animals. With the development of the cre/loxP and flp/FRT systems, it has become possible to excise defined DNA fragments from the genome of specified cells. Cre and Flp are bacterial and yeast recombinases, respectively, which recognize loxP and FRT sequences, respectively. The most common... 

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