Ilya Zakharov-Gezekhus | Moscow State University (original) (raw)
Papers by Ilya Zakharov-Gezekhus
Genetika, 2004
Intergeneric, interspecific, and intraspecific genetic variation of the 310-bp 3'-end region ... more Intergeneric, interspecific, and intraspecific genetic variation of the 310-bp 3'-end region of the mitochondrial gene of cytochrome oxidase I (COI) has been assessed in ladybirds (Coleoptera: Coccinnellidae). The phylogenetic distances between eight species of ladybirds have been determined. Mitochondrial DNA (mtDNA) nucleotide sequences have been compared in Adalia bipunctata L. differing in the elytron and pronotum colors that have been sampled from several geographically remote populations. The taxonomic statuses of two morphs from the genus Adalia, A. bipunctata bipunctata and A. bipunctata fasciatopunctata, have been identified.
Ecological genetics, 2010
Konstantin Mereschkowsky suggested that the plastids originate from symbiotic cyanobacteria, and ... more Konstantin Mereschkowsky suggested that the plastids originate from symbiotic cyanobacteria, and the nucleus has also originated from an endosymbiont. The hypothesis of nuclear symbiogenesis was not discussed till 1980ies. Later (Gupta et al.,1994;. Lopez-Garcia, Moreira, 2001) the data were obtained in favor of the hypothesis that the nucleus originated from an archaean captured to become an endosymbiont of a bacterial host. Short biography of Konstantin Mereschkowsky is included.
Ecological genetics
Polymorphism of the mtDNA gene COI was studied in a St. Petersburg population of two spot ladybir... more Polymorphism of the mtDNA gene COI was studied in a St. Petersburg population of two spot ladybird Adalia bipunctata and analyzed in relation with the presence of a symbiotic bacterium Spiroplasma. Variable nucleotide sequences in the middle part of the gene COI formed 13 mitotypes. 84 ladybirds were studied, 21 of these were found to be infected by Spiroplasma. Mean pairwise difference of nucleotides in the COI sequence was 0.001 for uninfected and 0.020 for infected individuals, thus mtDNA polymorphism was considerably higher among uninfected ladybirds compared with infected ones.
Genetics, 2002
The two-spot ladybird beetle Adalia bipunctata (Coleoptera: Coccinellidae) is host to four differ... more The two-spot ladybird beetle Adalia bipunctata (Coleoptera: Coccinellidae) is host to four different intracellular maternally inherited bacteria that kill male hosts during embryogenesis: one each of the genus Rickettsia (α-Proteobacteria) and Spiroplasma (Mollicutes) and two distinct strains of Wolbachia (α-Proteobacteria). The history of infection with these male-killers was explored using host mitochondrial DNA, which is linked with the bacteria due to joint maternal inheritance. Two variable regions, 610 bp of cytochrome oxidase subunit I and 563 bp of NADH dehydrogenase subunit 5, were isolated from 52 A. bipunctata with known infection status and different geographic origin from across Eurasia. Two outgroup taxa were also considered. DNA sequence analysis revealed that the distribution of mitochondrial haplotypes is not associated with geography. Rather, it correlates with infection status, confirming linkage disequilibrium between mitochondria and bacteria. The data strongly ...
Moscow University Biological Sciences Bulletin, 2010
The geographic variability of Harmonia axyridis Pall. has been studied with regard to three mor p... more The geographic variability of Harmonia axyridis Pall. has been studied with regard to three mor phological features. A study of the cytochrome C oxidase subunit I (COI) polymorphism was begun. Two geo graphically separated zones inside the Russian part of the geographic range of the species are recognized. Interpopulational differences, as judged using polymorphic traits, are very small within each zone. In con trast, the differences between the populations of the western and eastern zones reach the subspecies level of. A zone of clinal variability of morphological traits is noted in Transbaikalia. It obviously resulted from sec ondary contact between the western and eastern groups of populations, which were separated during the last glaciation and then rejoined.
Russian Journal of Genetics: Applied Research, 2012
An mtDNA polymorphism (according to the COI gene) of the two spot ladybird beetle (Adalia bipunct... more An mtDNA polymorphism (according to the COI gene) of the two spot ladybird beetle (Adalia bipunctata) St. Petersburg population has been studied, as well as the infection rate with the symbiotic bacte rium Spiroplasma. In total, 13 mitotypes differing in the nucleotide sequence of the middle part of the COI gene have been found. Of the 84 examined ladybird beetles, 21 were infected by Spiroplasma. The mean pair wise difference of the COI nucleotide sequences for the infected ladybird beetles is 0.001, and for the unin fected individuals it is 0.020; thus, the mtDNA polymorphism is considerably higher among the uninfected cohort as compared with the infected one.
Russian Journal of Genetics, 2014
The mitochondrial DNA phylogenies of closely related forms of mosquitoes from the Culex pipiens c... more The mitochondrial DNA phylogenies of closely related forms of mosquitoes from the Culex pipiens complex and of strains of the endosymbiotic bacteria Wolbachia pipientis were compared. Based on the cytochrome oxidase subunit I gene polymorphism, six mitochondrial haplotypes and four W. pipientis groups were discovered in mosquitoes from geographically remote populations. A strict correlation between the COI type and the type of W. pipientis proves the stable coinheritance and distribution of both cytoplasmic components in the examined mosquito populations and suggests either the absence or rarity of horizontal transfer of the symbionts in the Culex pipiens complex.
Doklady Akademii nauk / [Rossiĭskaia akademii nauk], 1998
Ecology and evolution, 2013
Introduction events can lead to admixture between genetically differentiated populations and bott... more Introduction events can lead to admixture between genetically differentiated populations and bottlenecks in population size. These processes can alter the adaptive potential of invasive species by shaping genetic variation, but more importantly, they can also directly affect mean population fitness either increasing it or decreasing it. Which outcome is observed depends on the structure of the genetic load of the species. The ladybird Harmonia axyridis is a good example of invasive species where introduced populations have gone through admixture and bottleneck events. We used laboratory experiments to manipulate the relatedness among H. axyridis parental individuals to assess the possibility for heterosis or outbreeding depression in F1 generation offspring for two traits related to fitness (lifetime performance and generation time). We found that inter-populations crosses had no major impact on the lifetime performance of the offspring produced by individuals from either native or ...
Zhurnal obshcheĭ biologii
Melanic polymorphism in Adalia bipunctata is usually said to result from cyclical seasonal select... more Melanic polymorphism in Adalia bipunctata is usually said to result from cyclical seasonal selection acting on the morphs: predominantly black individuals gain a reproductive advantage in the spring and summer, red forms gaining an advantage during the winter. The veracity of this proposition is based largely on a series of samples taken in Berlin-Buch in the 1930s by Timofeeff-Ressovsky (1940). These show considerable and reasonably consistent cyclical changes in the frequency of the morphs. We here give morph frequency data from sites in Russia and Britain, as well as citing data from Berlin-Buch (Schummer, 1983) which show no indication of the seasonal selection postulated by Timofeeff-Ressovsky. We discuss the possible explanations of these contradictory data sets and consider the mechanisms which might account for the maintenance of melanic polymorphism in A. bipunctata in the absence of cyclical thermal melanism.
Genetika, 2000
Some of the male-killing lines of the two-spot ladybird Adalia bipunctata L. isolated from the po... more Some of the male-killing lines of the two-spot ladybird Adalia bipunctata L. isolated from the populations of Moscow and Tomsk and having a female-biased sex ratio were found to be infected with a bacterium of the genus Wolbachia. This fact is the first demonstration of the ability of Wolbachia to kill males of a host insect. The coexistence of females infected with different male-killing bacteria was recorded in the population of Moscow.
Genetika, 2000
Two-spot ladybirds Adalia bipunctata were collected from the populations of Western and Eastern E... more Two-spot ladybirds Adalia bipunctata were collected from the populations of Western and Eastern Europe and Central Asia. The agent killing males at the early embryonic stage in these populations was identified as bacteria of the genus Spiroplasma. Bacteria found in A. bipunctata proved to be phylogenetically related to Spiroplasma ixodetis (typical line Y-32) found in tick Ixodes pacificus but not to Spiroplasma causing the death of male embryos in Drosophila.
Genetika, 1999
In populations of Harmonia axyridis Pall. from Novosibirsk and Kyzyl, females (three out of 34 st... more In populations of Harmonia axyridis Pall. from Novosibirsk and Kyzyl, females (three out of 34 studied) that produce exclusively female progeny were found. In one of the families studied, the inheritance of the male-killing trait was monitored over five generations. The male-killing trait was maternally inherited. The beetles of this family were infected with the bacteria that, according to the sequence analysis of the gene fragment for 16S rRNA, belong to the genus Spiroplasma (VI group).
Doklady Biological Sciences, 2003
Russian Journal of Genetics, 2009
Quantitative methods of estimation of similarity between gene orders have been used to compare th... more Quantitative methods of estimation of similarity between gene orders have been used to compare the genomes of 14 strains of mycoplasmas and 2 strains of phytoplasmas, i.e., all genomes of bacteria of the class Mollicutes deciphered to date. Reconstructions of the mycoplasma phylogeny based on comparisons of (a) gene orders in a chromosome and (b) nucleotide or amino acid sequences have proved to be almost identical, which confirms that quantitative measures of gene order similarity can be used for meaningful phylogenetic reconstructions. Genomic rearrangements have been almost equally frequent in the evolutions of three main groups of mycoplasmas. A gene order changes by 1% approximately every 7 Myr or less (the calculation is based on the assumption that a 1% change in the nucleotide sequence of the 16S rRNA gene requires, on average, 50 Myr). In contrast to another analyzed group of obligately parasitic bacteria (rickettsiae), no distinct tendency towards a decrease in the rate of genomic rearrangements has been found in the evolution of mycoplasmas.
Russian Journal of Genetics, 2006
Mitochondrial DNA variation was examined in one of the southern most populations of domestic rein... more Mitochondrial DNA variation was examined in one of the southern most populations of domestic reindeer, inhabiting Tyva Republic (Tuva). In Tuvinian population sequence polymorphism of the mitochondrial DNA D loop region was demonstrated. In a sample of 29 individuals 7 mitotypes were distinguished, pointing to the preservation of rather high level of genetic diversity in this population.
Russian Journal of Genetics, 2005
Genetic characteristics of intratetrad mating, i.e., fusion of haploid products of one meiotic di... more Genetic characteristics of intratetrad mating, i.e., fusion of haploid products of one meiotic division, are considered. Upon intratetrad mating, the probability of homozygotization is lower than that upon self-fertilization, while heterozygosity at genes linked to the mating-type locus, which determines the possibility of cell fusion, is preserved. If the mating-type locus is linked to the centromere, the genome regions adjoining the centromeres of all chromosomes remain heterozygous. Intratetrad mating is characteristic of a number of fungi (Saccharomyces cerevisiae, Saccharomycodes ludwigii, Neurospora tetrasperma, Agaricus bisporus, Microbotryum violaceum , and others). Parthenogenetic reproduction in some insects also involves this type of fusion of nuclei. Intratetrad mating leads to the accumulation of haplolethals (i.e., lethals manifesting in haploid cells but not hindering their mating) in pericentric chromosome regions. Since heterozygosity increases viability of an organism, recombination has been suppressed during evolution in fungi characterized by intratetrad mating, which ensures heterozygosity of the most part of the genome.
Russian Journal of Genetics, 2008
Data reflecting evolutionary changes in chromosomal gene order can be used for phylogenetic recon... more Data reflecting evolutionary changes in chromosomal gene order can be used for phylogenetic reconstructions along with the results of nucleotide sequence comparison. By the example of bacteria of the genus Rickettsia , we have shown that phylogenetic reconstructions based on quantitative estimates of the similarity and cladistic analysis of gene order data, may, in some cases, amend and fill up classical phylogenetic trees. When applied, these approaches enabled us to substantiate the hypothesis that Rickettsia felis species had split before the typhus (R. typhi, R. prowazekii) and spotted fever (R. connorii) group divergence and thus R. felis does not belong to the latter group. In general, rickettsias evolved towards increasing intracellular parasitic specialization. Five Rickettsia species whose genomes have been sequenced and annotated completely actually form an evolutionary series R. bellii-R. felis-R. conorii-R. prowazekii-R. typhi. Within this series, a reduction in genome size and rapid decrease of genome rearrangement rates (genome plasticity loss) gradually occur.
Russian Journal of Genetics, 2009
Genomes of 23 strains of cyanobacteria were comparatively analyzed using quantitative methods of ... more Genomes of 23 strains of cyanobacteria were comparatively analyzed using quantitative methods of estimation of gene order similarity. It has been found that reconstructions of phylogenesis of cyanobacteria based on the comparison of the orders of genes in chromosomes and nucleotide sequences appear to be similar. This confirms the applicability of quantitative measures of similarity of gene orders for phylogenetic reconstructions. In the evolution of marine unicellular planktonic cyanobacteria, genome rearrangements are fixed with a low rate (about 3% of gene order changes per 1% of 16S rRNA changes), whereas in other groups of cyanobacteria the gene order can change several times more rapidly. The gene orders in genomes of cyanobacteria and chloroplasts preserve a considerable degree of similarity. The closest relatives of chloroplasts among the analyzed cyanobacteria are likely to be strains from hot springs belonging to the genus Synechococcus. Comparative analysis of gene orders and nucleotide sequences strongly suggests that Synechococcus strains from different environments (sea, fresh waters, hot springs) are not related and belong to evolutionally distant lines.
Russian Journal of Genetics, 2006
1329 Studies devoted to scientific and organizational activities of Sos Isaakovich Alikhanyan, an... more 1329 Studies devoted to scientific and organizational activities of Sos Isaakovich Alikhanyan, an outstanding Russian geneticist, present very scanty information on his work during the Stalin period, when the antigenetics campaign was actively expanded. As is known, Alikhanyan began his scientific work in 1931 in the Department of Genetics and Breeding of Moscow State University, headed by A.S. Serebrovsky. Alikhanyan’s research interests were very diverse, including the gene problem, inheritance of qualitative and quantitative characters in animals, and breeding. His candidate’s dissertation was devoted to basic genetic problems and was performed on Drosophila (“Study on Lethal Mutations in the Sex Chromosome Left End in Drosophila melanogaster ,” 1936). In 1937, Alikhanyan received a candidate’s degree in biology and in 1940, an academic rank of associate professor.
Genetika, 2004
Intergeneric, interspecific, and intraspecific genetic variation of the 310-bp 3'-end region ... more Intergeneric, interspecific, and intraspecific genetic variation of the 310-bp 3'-end region of the mitochondrial gene of cytochrome oxidase I (COI) has been assessed in ladybirds (Coleoptera: Coccinnellidae). The phylogenetic distances between eight species of ladybirds have been determined. Mitochondrial DNA (mtDNA) nucleotide sequences have been compared in Adalia bipunctata L. differing in the elytron and pronotum colors that have been sampled from several geographically remote populations. The taxonomic statuses of two morphs from the genus Adalia, A. bipunctata bipunctata and A. bipunctata fasciatopunctata, have been identified.
Ecological genetics, 2010
Konstantin Mereschkowsky suggested that the plastids originate from symbiotic cyanobacteria, and ... more Konstantin Mereschkowsky suggested that the plastids originate from symbiotic cyanobacteria, and the nucleus has also originated from an endosymbiont. The hypothesis of nuclear symbiogenesis was not discussed till 1980ies. Later (Gupta et al.,1994;. Lopez-Garcia, Moreira, 2001) the data were obtained in favor of the hypothesis that the nucleus originated from an archaean captured to become an endosymbiont of a bacterial host. Short biography of Konstantin Mereschkowsky is included.
Ecological genetics
Polymorphism of the mtDNA gene COI was studied in a St. Petersburg population of two spot ladybir... more Polymorphism of the mtDNA gene COI was studied in a St. Petersburg population of two spot ladybird Adalia bipunctata and analyzed in relation with the presence of a symbiotic bacterium Spiroplasma. Variable nucleotide sequences in the middle part of the gene COI formed 13 mitotypes. 84 ladybirds were studied, 21 of these were found to be infected by Spiroplasma. Mean pairwise difference of nucleotides in the COI sequence was 0.001 for uninfected and 0.020 for infected individuals, thus mtDNA polymorphism was considerably higher among uninfected ladybirds compared with infected ones.
Genetics, 2002
The two-spot ladybird beetle Adalia bipunctata (Coleoptera: Coccinellidae) is host to four differ... more The two-spot ladybird beetle Adalia bipunctata (Coleoptera: Coccinellidae) is host to four different intracellular maternally inherited bacteria that kill male hosts during embryogenesis: one each of the genus Rickettsia (α-Proteobacteria) and Spiroplasma (Mollicutes) and two distinct strains of Wolbachia (α-Proteobacteria). The history of infection with these male-killers was explored using host mitochondrial DNA, which is linked with the bacteria due to joint maternal inheritance. Two variable regions, 610 bp of cytochrome oxidase subunit I and 563 bp of NADH dehydrogenase subunit 5, were isolated from 52 A. bipunctata with known infection status and different geographic origin from across Eurasia. Two outgroup taxa were also considered. DNA sequence analysis revealed that the distribution of mitochondrial haplotypes is not associated with geography. Rather, it correlates with infection status, confirming linkage disequilibrium between mitochondria and bacteria. The data strongly ...
Moscow University Biological Sciences Bulletin, 2010
The geographic variability of Harmonia axyridis Pall. has been studied with regard to three mor p... more The geographic variability of Harmonia axyridis Pall. has been studied with regard to three mor phological features. A study of the cytochrome C oxidase subunit I (COI) polymorphism was begun. Two geo graphically separated zones inside the Russian part of the geographic range of the species are recognized. Interpopulational differences, as judged using polymorphic traits, are very small within each zone. In con trast, the differences between the populations of the western and eastern zones reach the subspecies level of. A zone of clinal variability of morphological traits is noted in Transbaikalia. It obviously resulted from sec ondary contact between the western and eastern groups of populations, which were separated during the last glaciation and then rejoined.
Russian Journal of Genetics: Applied Research, 2012
An mtDNA polymorphism (according to the COI gene) of the two spot ladybird beetle (Adalia bipunct... more An mtDNA polymorphism (according to the COI gene) of the two spot ladybird beetle (Adalia bipunctata) St. Petersburg population has been studied, as well as the infection rate with the symbiotic bacte rium Spiroplasma. In total, 13 mitotypes differing in the nucleotide sequence of the middle part of the COI gene have been found. Of the 84 examined ladybird beetles, 21 were infected by Spiroplasma. The mean pair wise difference of the COI nucleotide sequences for the infected ladybird beetles is 0.001, and for the unin fected individuals it is 0.020; thus, the mtDNA polymorphism is considerably higher among the uninfected cohort as compared with the infected one.
Russian Journal of Genetics, 2014
The mitochondrial DNA phylogenies of closely related forms of mosquitoes from the Culex pipiens c... more The mitochondrial DNA phylogenies of closely related forms of mosquitoes from the Culex pipiens complex and of strains of the endosymbiotic bacteria Wolbachia pipientis were compared. Based on the cytochrome oxidase subunit I gene polymorphism, six mitochondrial haplotypes and four W. pipientis groups were discovered in mosquitoes from geographically remote populations. A strict correlation between the COI type and the type of W. pipientis proves the stable coinheritance and distribution of both cytoplasmic components in the examined mosquito populations and suggests either the absence or rarity of horizontal transfer of the symbionts in the Culex pipiens complex.
Doklady Akademii nauk / [Rossiĭskaia akademii nauk], 1998
Ecology and evolution, 2013
Introduction events can lead to admixture between genetically differentiated populations and bott... more Introduction events can lead to admixture between genetically differentiated populations and bottlenecks in population size. These processes can alter the adaptive potential of invasive species by shaping genetic variation, but more importantly, they can also directly affect mean population fitness either increasing it or decreasing it. Which outcome is observed depends on the structure of the genetic load of the species. The ladybird Harmonia axyridis is a good example of invasive species where introduced populations have gone through admixture and bottleneck events. We used laboratory experiments to manipulate the relatedness among H. axyridis parental individuals to assess the possibility for heterosis or outbreeding depression in F1 generation offspring for two traits related to fitness (lifetime performance and generation time). We found that inter-populations crosses had no major impact on the lifetime performance of the offspring produced by individuals from either native or ...
Zhurnal obshcheĭ biologii
Melanic polymorphism in Adalia bipunctata is usually said to result from cyclical seasonal select... more Melanic polymorphism in Adalia bipunctata is usually said to result from cyclical seasonal selection acting on the morphs: predominantly black individuals gain a reproductive advantage in the spring and summer, red forms gaining an advantage during the winter. The veracity of this proposition is based largely on a series of samples taken in Berlin-Buch in the 1930s by Timofeeff-Ressovsky (1940). These show considerable and reasonably consistent cyclical changes in the frequency of the morphs. We here give morph frequency data from sites in Russia and Britain, as well as citing data from Berlin-Buch (Schummer, 1983) which show no indication of the seasonal selection postulated by Timofeeff-Ressovsky. We discuss the possible explanations of these contradictory data sets and consider the mechanisms which might account for the maintenance of melanic polymorphism in A. bipunctata in the absence of cyclical thermal melanism.
Genetika, 2000
Some of the male-killing lines of the two-spot ladybird Adalia bipunctata L. isolated from the po... more Some of the male-killing lines of the two-spot ladybird Adalia bipunctata L. isolated from the populations of Moscow and Tomsk and having a female-biased sex ratio were found to be infected with a bacterium of the genus Wolbachia. This fact is the first demonstration of the ability of Wolbachia to kill males of a host insect. The coexistence of females infected with different male-killing bacteria was recorded in the population of Moscow.
Genetika, 2000
Two-spot ladybirds Adalia bipunctata were collected from the populations of Western and Eastern E... more Two-spot ladybirds Adalia bipunctata were collected from the populations of Western and Eastern Europe and Central Asia. The agent killing males at the early embryonic stage in these populations was identified as bacteria of the genus Spiroplasma. Bacteria found in A. bipunctata proved to be phylogenetically related to Spiroplasma ixodetis (typical line Y-32) found in tick Ixodes pacificus but not to Spiroplasma causing the death of male embryos in Drosophila.
Genetika, 1999
In populations of Harmonia axyridis Pall. from Novosibirsk and Kyzyl, females (three out of 34 st... more In populations of Harmonia axyridis Pall. from Novosibirsk and Kyzyl, females (three out of 34 studied) that produce exclusively female progeny were found. In one of the families studied, the inheritance of the male-killing trait was monitored over five generations. The male-killing trait was maternally inherited. The beetles of this family were infected with the bacteria that, according to the sequence analysis of the gene fragment for 16S rRNA, belong to the genus Spiroplasma (VI group).
Doklady Biological Sciences, 2003
Russian Journal of Genetics, 2009
Quantitative methods of estimation of similarity between gene orders have been used to compare th... more Quantitative methods of estimation of similarity between gene orders have been used to compare the genomes of 14 strains of mycoplasmas and 2 strains of phytoplasmas, i.e., all genomes of bacteria of the class Mollicutes deciphered to date. Reconstructions of the mycoplasma phylogeny based on comparisons of (a) gene orders in a chromosome and (b) nucleotide or amino acid sequences have proved to be almost identical, which confirms that quantitative measures of gene order similarity can be used for meaningful phylogenetic reconstructions. Genomic rearrangements have been almost equally frequent in the evolutions of three main groups of mycoplasmas. A gene order changes by 1% approximately every 7 Myr or less (the calculation is based on the assumption that a 1% change in the nucleotide sequence of the 16S rRNA gene requires, on average, 50 Myr). In contrast to another analyzed group of obligately parasitic bacteria (rickettsiae), no distinct tendency towards a decrease in the rate of genomic rearrangements has been found in the evolution of mycoplasmas.
Russian Journal of Genetics, 2006
Mitochondrial DNA variation was examined in one of the southern most populations of domestic rein... more Mitochondrial DNA variation was examined in one of the southern most populations of domestic reindeer, inhabiting Tyva Republic (Tuva). In Tuvinian population sequence polymorphism of the mitochondrial DNA D loop region was demonstrated. In a sample of 29 individuals 7 mitotypes were distinguished, pointing to the preservation of rather high level of genetic diversity in this population.
Russian Journal of Genetics, 2005
Genetic characteristics of intratetrad mating, i.e., fusion of haploid products of one meiotic di... more Genetic characteristics of intratetrad mating, i.e., fusion of haploid products of one meiotic division, are considered. Upon intratetrad mating, the probability of homozygotization is lower than that upon self-fertilization, while heterozygosity at genes linked to the mating-type locus, which determines the possibility of cell fusion, is preserved. If the mating-type locus is linked to the centromere, the genome regions adjoining the centromeres of all chromosomes remain heterozygous. Intratetrad mating is characteristic of a number of fungi (Saccharomyces cerevisiae, Saccharomycodes ludwigii, Neurospora tetrasperma, Agaricus bisporus, Microbotryum violaceum , and others). Parthenogenetic reproduction in some insects also involves this type of fusion of nuclei. Intratetrad mating leads to the accumulation of haplolethals (i.e., lethals manifesting in haploid cells but not hindering their mating) in pericentric chromosome regions. Since heterozygosity increases viability of an organism, recombination has been suppressed during evolution in fungi characterized by intratetrad mating, which ensures heterozygosity of the most part of the genome.
Russian Journal of Genetics, 2008
Data reflecting evolutionary changes in chromosomal gene order can be used for phylogenetic recon... more Data reflecting evolutionary changes in chromosomal gene order can be used for phylogenetic reconstructions along with the results of nucleotide sequence comparison. By the example of bacteria of the genus Rickettsia , we have shown that phylogenetic reconstructions based on quantitative estimates of the similarity and cladistic analysis of gene order data, may, in some cases, amend and fill up classical phylogenetic trees. When applied, these approaches enabled us to substantiate the hypothesis that Rickettsia felis species had split before the typhus (R. typhi, R. prowazekii) and spotted fever (R. connorii) group divergence and thus R. felis does not belong to the latter group. In general, rickettsias evolved towards increasing intracellular parasitic specialization. Five Rickettsia species whose genomes have been sequenced and annotated completely actually form an evolutionary series R. bellii-R. felis-R. conorii-R. prowazekii-R. typhi. Within this series, a reduction in genome size and rapid decrease of genome rearrangement rates (genome plasticity loss) gradually occur.
Russian Journal of Genetics, 2009
Genomes of 23 strains of cyanobacteria were comparatively analyzed using quantitative methods of ... more Genomes of 23 strains of cyanobacteria were comparatively analyzed using quantitative methods of estimation of gene order similarity. It has been found that reconstructions of phylogenesis of cyanobacteria based on the comparison of the orders of genes in chromosomes and nucleotide sequences appear to be similar. This confirms the applicability of quantitative measures of similarity of gene orders for phylogenetic reconstructions. In the evolution of marine unicellular planktonic cyanobacteria, genome rearrangements are fixed with a low rate (about 3% of gene order changes per 1% of 16S rRNA changes), whereas in other groups of cyanobacteria the gene order can change several times more rapidly. The gene orders in genomes of cyanobacteria and chloroplasts preserve a considerable degree of similarity. The closest relatives of chloroplasts among the analyzed cyanobacteria are likely to be strains from hot springs belonging to the genus Synechococcus. Comparative analysis of gene orders and nucleotide sequences strongly suggests that Synechococcus strains from different environments (sea, fresh waters, hot springs) are not related and belong to evolutionally distant lines.
Russian Journal of Genetics, 2006
1329 Studies devoted to scientific and organizational activities of Sos Isaakovich Alikhanyan, an... more 1329 Studies devoted to scientific and organizational activities of Sos Isaakovich Alikhanyan, an outstanding Russian geneticist, present very scanty information on his work during the Stalin period, when the antigenetics campaign was actively expanded. As is known, Alikhanyan began his scientific work in 1931 in the Department of Genetics and Breeding of Moscow State University, headed by A.S. Serebrovsky. Alikhanyan’s research interests were very diverse, including the gene problem, inheritance of qualitative and quantitative characters in animals, and breeding. His candidate’s dissertation was devoted to basic genetic problems and was performed on Drosophila (“Study on Lethal Mutations in the Sex Chromosome Left End in Drosophila melanogaster ,” 1936). In 1937, Alikhanyan received a candidate’s degree in biology and in 1940, an academic rank of associate professor.