Sequence heterogeneity

Bessho, Y., Tamura, S., Hori, H., Tanaka, H., Ohama, T. and Osawa, S. (1997) Planarian mitochondria sequence heterogeneity relationships between the type of cytochrome c oxidase subunit 1 gene sequence, karyotype and genital organ. Molecular Ecology 6, 1 29-1 36. 

Kramer, F. and Schnieder, T. (1998) Sequence heterogeneity in a repetitive DNA element of Fasciola. International journal for Parasitology 28, 1923-1 929. 

From studies done primarily in S. cerevisiae, it is clear that ectopic recombination events occur at frequencies that are high relative to mutation frequencies. These events, therefore, are likely to be important in concerted evolution and perhaps in other types of evolutionarily important processes (e.g., genome rearrangements). The genetic control of ectopic recombination as well as the effects of repeat size and/or sequence heterogeneity on the frequency and types of ectopic recombination are active areas of investigation. 

The rate of renaturation depends on the concentration of complementary sequences. Viral DNA has a smaller variety of sequences than does bacterial DNA this reflects the higher level of genetic complexity in bacteria. Thus, for viral and bacterial DNA fragments of the same average size and at the same molar concentration, there would be a higher concentration of complementary sequences in the former. Viral DNA therefore would renature faster than bacterial DNA. In other words, bacterial DNA has greater sequence heterogeneity. 

Rates of renaturation and sequence heterogeneity (or complexity) can be examined quantitatively through COT analysis. If Q is the initial concentration of DNA (moles per liter DNA phosphate) and k is the rate constant for association of the complementary strands, it can be shown that the fraction / of single-stranded molecules decreases with time t (s) according to the expression... 

Why does viral DNA have less sequence heterogeneity than does bacterial DNA SOLUTION... 

The genome of viruses carries fewer genes than does that of bacteria. Thus, in a fixed amount of DNA (say several viral genome equivalents), viral genes would be present in more copies than would individual bacterial genes. Different genes have different nucleotide sequences, but various sequences would be repeated more frequently in the viral DNA i.e., it would have less sequence heterogeneity. 

The small AFGP components, 6, 7, and 8, all had some prolines following threonines, and existed, at least primarily, as easily separable species. Sequence heterogeneity has been found with regard to the prolines (28) (Figure 3). 

Since the WalkThrough chains are a population of fragments that each stops at every position of the template molecules, they are uniform in their positional preference and lack a sequence bias. This sequence heterogeneity allows crossover to occur more randomly. 

CoDolvmer Characterization. The base-catalyzed hydrolysis reaction of polyacrylamide has been studied by several workers (27-29). Halverson, et al. (29) concluded from Interpretations of C NHR spectra that a well-spaced distribution of acrylate groups Is produced along the polymer chain. This hydrolysis procedure offered an opportunity to prepare nearly model copolymers free of chemical sequence heterogeneity. 

Steinert M, Van Assel S. Sequence heterogeneity in kinetoplast DNA Reassociation kinetics. Plasmid 1980 3 7-17. 

Kidane GZ, Ht es D, Simpson L. Sequence heterogeneity and anomalous dectrophoretic mobility of kinetoplast minidrde DNA from Leishmania tarentolae. Gene 1984 27 265-77. 

S. H. J. Bauer, X. Y. Zhang, W. Van Donngen, and M. Claeys, Chromogranin A from bovine adrenal medulla molecular charactaization of glycosylations, phosphorylations, and sequence heterogeneities by mass spectrometry. Anal. Biochem. 274, 69-80 (1999). 

Schultz, G. A. (1969), Base sequence heterogeneity in avian DNA. Ph.D. thesis. 

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