Molecular Evolution Activities
 

This is a comprehensive bibliography (under construction) of primary and secondary sources on the neutral theory of molecular evolution. It currently covers the period 1973-2001.

Author :

Moriyama, E. N.;Powell, J. R.

Year :

1996

Title :

Intraspecific nuclear DNA variation in Drosophila

Journal :

Molecular Biology and Evolution

Volume :

13

Issue :

1

Pages :

261-277

Date :

Jan

Short Title :

Intraspecific nuclear DNA variation in Drosophila

Alternate Journal :

Mol. Biol. Evol.

Custom 2 :

ISI:A1996TP07600025

Abstract :

We have summarized and analyzed all available nuclear DNA sequence polymorphism studies for three species of Drosophila, D. melanogaster (24 loci), D. simulans (12 loci), and D. pseudoobscura (5 loci). Our major findings are: (1) The average nucleotide heterozygosity ranges from about 0.4% to 2% depending upon species and function of the region, i.e., coding or noncoding. (2) Compared to D. simulans and D. pseudoobscura (which are about equally variable), D. melanogaster displays a low degree of DNA polymorphism. (3) Noncoding introns and 3' and 5' flanking DNA shows less polymorphism than silent sites within coding DNA. (4) X-linked genes are less variable than autosomal genes. (5) Transition (Ts) and transversion (Tv) polymorphisms are about equally frequent in noncoding DNA and at fourfold degenerate sites in coding DNA while Ts polymorphisms outnumber Tv polymorphisms by about 2:1 in total coding DNA. The increased Ts polymorphism in coding regions is likely due to the structure of the genetic code: silent changes are more often Ts's than are replacement substitutions. (6) The proportion of replacement polymorphisms is significantly higher in D. melanogaster than in D. simulans. (7) The level of variation in coding DNA and the adjacent noncoding DNA is significantly correlated indicating regional effects, most notably recombination. (8) Surprisingly, the level of polymorphism at silent coding sites in D. melanogaster is positively correlated with degree of codon usage bias. (9) Three proposed tests of the neutral theory of DNA polymorphisms have been performed on the data: Tajima's test, the HKA test, and the McDonald-Kreitman test. About half of the loci fail to conform to the expectations of neutral theory by one of the tests. We conclude that many variables are affecting levels of DNA polymorphism in Drosophila, from properties of nucleotides to population history and, perhaps, mating structure. No simple, all encompassing explanation satisfactorily accounts for the data.

Notes :

Times Cited: 133 TP076 MOL BIOL EVOL
 -- contributed by John Beatty, March 29, 2002