RESUMO
The modern concept of intercalary heterochromatin as polytene chromosome regions exhibiting a number of specific characteristics is formulated. DNA constituting these regions is replicated late in the S period; therefore, some strands of polytene chromosomes are underrepresented; i.e., they are underreplicated. Late-replicating regions account for about 7% of the genome; genes are located there in clusters of as many as 40. In general, the gene density in the clusters is substantially lower than in the main part of the genome. Late-replicating regions have an inactivating capacity: genes incorporated into these regions as parts of transposons are inactivated with a higher probability. These regions contain a specific protein SUUR affecting the rate of replication completion.
Assuntos
Replicação do DNA/fisiologia , DNA/genética , Genoma de Inseto/fisiologia , Cromossomos Politênicos/genética , Fase S/fisiologia , Animais , DNA/biossíntese , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster , Cromossomos Politênicos/metabolismoAssuntos
Proteínas de Ligação a DNA/genética , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Genes de Insetos , Animais , Montagem e Desmontagem da Cromatina , Cromossomos/genética , Cromossomos/metabolismo , Cromossomos/ultraestrutura , Drosophila melanogaster/metabolismo , Drosophila melanogaster/ultraestrutura , Expressão Gênica , Heterocromatina/genética , Heterocromatina/metabolismo , Heterocromatina/ultraestruturaRESUMO
The results of a comparative study of cloned DNA fragments of Drosophila simulans, D. mauritiana, D. teissieri, and D. erecta are presented. The fragments were amplified in PCR with primers specified to the region of D. melanogaster interband 61C7/C8. The uniqueness of all cloned fragments in the genomes of these species was confirmed. A comparative analysis of nucleotide sequences revealed that the rate of evolution of DNA from D. melanogaster interband 61C7/C8 is close to the rate of neutral evolution in the genus Drosophila.
