Structural-Genetical Mosaicism

Mosaicism is very often caused by somatic mutation. The same types of mutation that occur in germ cells may also occur in somatic cells (Shapiro, 1966). The frequency of mutation in vitro in somatic cells is similar to the frequency in vivo in germ cells. Cell clones can result from the division of somatic cell mutants. These mutants may somehow change the direction of development. The mutants will also change the observed phenotype (Searle, 1968). 

Mosaicism in female mice homozygous for the recessive nonagouti color gene (aa) is a well-analyzed example of such mutations (Bhat, 1949). The mosaic individual has an agouti spot which is caused by the somatic mutation a- (Fig. 66). 

Gene Type of mutation Type of mosaic Sex Strain origin Ratio of normal mutant gametes 

The progeny of mutant cells is incorporated into a hair folhcle in a certain body region. It is of interest that the somatic mutation which occurred during early em-bryogenesis can affect cells that are predecessors for both germ and somatic cells (Russell, 1964). Several examples of such somatic mutations are known for mice (Table 32). Similar mutations are known for Drosophila (Altenburg and Browning, 1961). 

Distributions of human embryonic cells leading to distinct mosaicism in complexes of sex chromosomes have been described (Fig. 67 Klinger and Schwar-zacher, 1962). Mosaics for differing karyotypes have also been described for the black fox (Volobuev and Radjabli, 1974). 

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All cases of mosaicism can be divided into two large groups if the classification of Russell (1964) is slightly modified (1) structural-genetical mosaicism where the... 

The best known case of structural-genetical mosaicism is the Lyonization which was discussed in Chap. 1.3.3.2. This phenomenon is characterized by the formation of cell clones which differ in X chromosome activities. 

Porter, S., Larue, L., and Mintz, B. (1991). Mosaicism of tyrosinase-locus transcription and chromatin structure in dark vs. light melanocyte clones of homozygous chinchilla-mottled mice. Dev. Genet. 12 393-402. 

The surface activity of proteins (as well as many of their other functions) depends on the so-called tertiary structure of protein molecules, which is determined by the spatial arrangement of their polypeptide chains. This tertiary molecular structure depends in turn on the primary protein structure - the aminoacid sequence, which is determined by the genetic code of a cell. The surface of a protein globule is mosaic-like it contains both polar... 

Ikemura T., Wada K.., Aota S. (1990). Giant G-i-C% mosaic structures of the human genome found by arrangement of GenBank human DNA sequences according to genetic positions. Genomics 8 207-216. 

Filamentous viruses, which are high-aspect ratio agents that proliferate in the presence of host cells, have regular self-assembled structures, and the viral coat proteins on their surface can be genetically or chemically modified to functionalise the nanovector. The tobacco mosaic virus is one of the most extensively studied ID structure for nanoscale applications, and their properties, functionalisation, and assembly into nanodevices are highlighted in the recent review by Ghodssi and co-workers. Mao and co-workers have recently demonstrated that filamentous bacteriophage can be converted into novel photo-responsive nanowires... 

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