عنوان

A molecular natural history of the P-element family in Drosophila melanogaster

TLpq303636332

انگلیسی

A molecular natural history of the P-element family in Drosophila melanogaster

[Thesis]

J. W. Ajioka

State University of New York at Stony Brook

1987

114

Ph.D.

State University of New York at Stony Brook

1987

Little information exists about the mechanisms that determine the fate of mobile elements in natural populations. The distribution of 352 P-elements across 63 X chromosomes were catalogued in samples drawn from two natural populations of Drosophila melanogaster. There is an extremely high occurrence of elements at the distal tip relative to the rest of the euchromatic chromosome. Moreover, the distribution of de novo insertions of the P-element on a specific laboratory chromosome is markedly different. In contrast, insertional data for the usd\piusd2 chromosome indicates an elevated rate associated with the distal site, although it does not appear sufficient to explain the large differential accumulation on wild chromosomes. This raises the issue of interchromosomal (or tip) variation in relative insertion rates, as well as the possibility that rates of elimination are lower at the distal tip. Proposals are suggested for resolving these competing views. The P-element occupies a site at the distal tip of the X chromosome in Drosophila melanogaster, at a frequency of about 75% and 98% in natural populations from North America (Mt. Sinai, NY and Homestead, FL) and Botswana, Africa, respectively. In contrast this site is occupied at a frequency of about 4 percent in a population from Tunisia. These results coupled with de novo insertion studies demonstrate that the behavior of the distal tip of the X chromosome may be quite variable as a target site for P-element insertion. A molecular analysis of P-element insertions in 19 X chromosome distal tips isolated from a Mt. Sinai, NY population was initiated. Whole genomic restriction mapping of these independent distal tips indicates most contain multiple P-element copies inserted into a common region. The analysis of the cloned distal tip P-element usd\lambdausd16BT suggest that a target site for insertion is present. Within usd\lambdausd16BT, the putative target sequence is 1.9 kb, is found only at the tips of chromosomes, varies between 0 and approximately 50 copies per genome and is associated with other moderately repetitive sequences in what appears to be a "clustered and scrambled" arrangement. X chromosome tips vary for the presence of this 1.9 kb sequence, which may, in part, explain the geographic variation in P-element occupancy of this site. (Abstract shortened with permission of author.)

Biological sciences

Biology

Biology

Genetics

J. W. Ajioka

p

[Thesis]

276903

a

Y