Biomedical subjects

E S Balakirev

Publications and source records attributed to E S Balakirev.

5 recordsLinked to original sources

PubMed2000

[Evaluation of genetic variability of the Kamchatka crab Paralithodes camtschaticus (Tilesius) using allozyme markers].

Interspecific genetic variation in populations of red king crab Paralithodes camtschaticus Tilesius (Litholidae, Decapoda: Crustacea) was examined using allozyme markers. The activity of 57 enzymes and the general protein presumably encoded by 92 loci was detected. The level of allozyme variability was low: the expected heterozygosity and the proportion of polymorphic loci were respectively 0.027 +/- 0.008 and 6.5%. This level of heterozygosity is three times lower than the average value for 122 crustacean species (0.082 +/- 0.007). Although genetic variants were found at 22 loci, their frequencies were generally low: only in loci 6-Pgd, Alp-1, and Pep-1 did the frequencies of the most common alleles not exceed 0.9. All polymorphic loci except one had two alleles; the exception was 6-Pgd, which had three alleles. The possible reasons for the low level of allozyme variability in red king crab are discussed.

Animals↗

PubMed1999

Molecular evolution of two linked genes, Est-6 and Sod, in Drosophila melanogaster.

We have obtained 15 sequences of Est-6 from a natural population of Drosophila melanogaster to test whether linkage disequilibrium exists between Est-6 and the closely linked Sod, and whether natural selection may be involved. An early experiment with allozymes had shown linkage disequilibrium between these two loci, while none was detected between other gene pairs. The Sod sequences for the same 15 haplotypes were obtained previously. The two genes exhibit similar levels of nucleotide polymorphism, but the patterns are different. In Est-6, there are nine amino acid replacement polymorphisms, one of which accounts for the S-F allozyme polymorphism. In Sod, there is only one replacement polymorphism, which corresponds to the S-F allozyme polymorphism. The transversion/transition ratio is more than five times larger in Sod than in Est-6. At the nucleotide level, the S and F alleles of Est-6 make up two allele families that are quite different from each other, while there is relatively little variation within each of them. There are also two families of alleles in Sod, one consisting of a subset of F alleles, and the other consisting of another subset of F alleles, designed F(A), plus all the S alleles. The Sod F(A) and S alleles are completely or nearly identical in nucleotide sequence, except for the replacement mutation that accounts for the allozyme difference. The two allele families have independent evolutionary histories in the two genes. There are traces of statistically significant linkage disequilibrium between the two genes that, we suggest, may have arisen as a consequence of selection favoring one particular sequence at each locus.

Animals↗

PubMed1996

Is esterase-P encoded by a cryptic pseudogene in Drosophila melanogaster?

We have amplified and sequenced the gene encoding Esterase-P (Est-P) in 10 strains of Drosophila melanogaster. Three premature termination codons occur in the coding region of the gene in two strains. This observation, together with other indirect evidence, leads us to propose that Est-P may be a pseudogene in D. melanogaster. Est-P would be a "cryptic" pseudogene, in the sense that it retains intact the coding sequence (without stop codons and other alterations usually observed in pseudogenes) in most D. melanogaster strains. We conjecture that the beta-esterase cluster may consist in other Drosophila species of functional and nonfunctional genes. We also conjecture that the rarity of detected pseudogenes in Drosophila may be due to the difficulty of discovering them, because most of them are cryptic.

Amino Acid Sequence↗

PubMed1995

[A simple method for detecting the order of relation location of fragments in constructing a paired restriction map].

A simple method for the ordering of fragments and the determination of relative positions of restriction sites when constructing pair restriction maps of linear and circular DNAs is described. The major advantages of the suggested approach as compared to the routine strategy of exhaustive search are as follows: (1) One does not need to begin the construction of the map by searching for the restrictases that produce the least number of fragments; (2) the method allows one to construct quite complicated maps, the main limiting parameter being the number of fragments during double digestion (no more than 10-12); and (3) construction of the map using this approach is less labor- and time-consuming than the routine strategy.

DNA↗

PubMedDate not supplied

[Pseudogenes: structure conservation, expression, and functions].

Pseudogenes have been defined as nonfunctional sequences of genomic DNA (junk DNA) originally derived from functional genes. It is therefore assumed that pseudogenes are not subject to natural selection and consequently pseudogene mutations are selectively neutral and have equal probability to become fixed in the population. We describe some unexpected features of pseudogenes in diverse organisms that are inconsistent with this widely accepted point of view. Pseudogenes are often evolutionary conserved and transcriptionally active. Moreover, pseudogenes that have been suitably investigated often exhibit functional roles, such as gene regulation, generation of genetic diversity, and other features that are expected in genes or DNA sequences that have functional roles. A review of the evidence leads to the conclusion that pseudogenes are important components of genomes, representing a repertoire of sequences available for functional evolution and subject to non-neutral evolutionary changes. Pseudogenes might be considered as potogenes, i.e. DNA sequences with a potentiality for becoming new genes or acquire new functions. Furthermore we conjecture that some pseudogenes along with their parental sequences may constitute sets of indivisible functionally interacting entities (intergenic complexes or "intergenes"), in which all the component elements are required in order to fulfill a collective functional role.

Animals↗