D-loop, region

Public databases for the analysis of animals used in food production do not exist. At the University of Davis-Califomia, a first database for canine mtDNA analysis is under construction. It has been shown that variations at the D-loop region exist in almost all species (Figure 6.8). Therefore, the analysis can lead to reliable results even if no database exists [8,9]. 

Example 2 A costumer declared that hairs were found at the surface of a beef meat he bought from a self-slaughtering butcher. By animal species determination, canine DNA was identified. Since the butcher and the customer both owned a dog, samples were taken from both and mtDNA analysis was performed of the canine D-loop region. The two dogs showed different sequences, but only the customer s dog showed the same sequence as the hairs found on the meat. Therefore, the butcher s dog could be excluded as the source of the hairs. 

Upholt WB, David IB (1977) Mapping of mitochondrial DNA of individual sheep and goats rapid evolution in the D loop regions of mitochondrial DNA. Cell 11 571-583... 

Figure 13.4 Schematic diagram (a) and topology diagram (b) of the polypeptide chain of cH-ras p21. The central p sheet of this a/p structure comprises six p strands, five of which are parallel a helices are green, p strands are blue, and the adenine, ribose, and phosphate parts of the GTP analog are blue, green, and ted, respectively. The loop regions that are involved in the activity of this protein are red and labeled Gl-GS. The Gl, G3, and G4 loops have the consensus sequences G-X-X-X-X-G-K-S/T, D-X-X-E, and N-K-X-D, respectively. (Adapted from E.R Pai et al., Nature 341 209-214, 1989.)...

The overall structure of the variable domain is very similar to that of the constant domain, hut there are nine p strands instead of seven. The two additional p strands are inserted into the loop region that connects p strands C and D (red in Figure 15.8). Functionally, this part of the polypeptide chain is important since it contains the hypervariahle region CDR2. The two extra p strands, called C and C", provide the framework that positions CDR2 close to the other two hypervariahle regions in the domain structure (Figure 15.8). 

FIGURE 12.34 A general diagram for the structure of tRNA. The positions of invariant bases as well as bases that seldom vary are shown in color. The numbering system is based on yeast tRNA R = purine Y= pyrimidine. Dotted lines denote sites in the D loop and variable loop regions where varying numbers of nucleotides are found in different tRNAs. 

Smicun, Y Campbell, S. D., Chen, M. A., Gu, H and Rudnick, G. (1999) The role of external loop regions in serotonin transport. Loop scanning mutagenesis of the serotonin transporter external domain../. Biol. Chem. 274, 36058-36064. 

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