PubMed Health⌕ Search

Biomedical subjects

E V Ananiev

Publications and source records attributed to E V Ananiev.

5 recordsLinked to original sources
PubMed1978

Reiterated genes with varying location in intercalary heterochromatin regions of Drosophila melanogaster polytene chromosomes.

The localization of two cloned D. melanogaster DNA fragments in polytene chromosomes was determined by means of in situ hybridization. These different fragments (Dm 225 and Dm 234B) are present in the genome in hundreds copies and contain genes whose transcription yields two different classes in abundant mRNA (Ilyin et al., 1976, 1977; Tchurikov et al., 1978). About 20--30 sites of these genes are demonstrable in the polytene chromosomes of a given stock. There are small but significant variations in the number and localization of these sites among individuals of the same stock. On the other hand, different stocks of D. melanogaster have an utterly different distribution of revealed hybridization sites in the polytene chromosomes. The location of both fragments (Dm 225 and Dm 234) was found to be virtually identical within any given stock of D. melanogaster. 69 sites for localization of Dm 225 or Dm 234 genes were detected in the chromosomes of 11 individuals studied. At least 50 (and up to 62) of them coincide with intercalary heterochromatin regions which are known to be characterized by ectopic pairing, late replication and the presence of "weak spots" in the chromosome. The ability of Dm225 and Dm 234 to code for the "abundant" classes of messenger RNA (Ilyin et al., 1976) and the fact that their location may coincide with the histone and ribosomal genes suggest that intercalary heterochromatin regions are "nests" containing various types of actively transcribable tandem-repeated genes coding for common "household" cell functions.

Animals↗
PubMed1978

The properties of gene Dm 225, a representative of dispersed repetitive genes in Drosophila melanogaster.

The properties of Dm 225 DNA, a fragment of D.melanogaster genome 2.9 kb in length excised by EcoRI endonuclease and cloned in the lambda gt phage or pMB9 plasmid, are described. The DNA hybridizes to a significant portion (0.8%) of total polysomal poly(A)(+)RNA (mRNA). The size of the hybridizing mRNA is about 2.3 kb (19S); it is present in the fraction of heavy polysomes. Dm 225 DNA fragments obtained with the aid of Hae III endonuclease have been mapped. mRNA hybridizes with all the fragments. In one of the end fragments, the 3'-end of mRNA has been localized and thus the direction of transcription determined. About 250 copies of the gene Dm 225 are present in the haploid genome of D.melanogaster, and all of them have the same size upon restriction with EcoRI endonuclease. On the other hand, the sequences of the genome adjacent to Dm 225 DNA are different and may vary from one cell line to another as evidenced by experiments in which the D.melanogaster DNA was restricted by Hind III endonuclease. In combination with in situ hybridization data /1,2/ the results obtained in this paper demonstrate that the structural gene present in Dm 225 DNA is a representative of a multiple gene family dispersed throughout the whole genome of D.melanogaster.Images

Animals↗
PubMed1977

Replication of chromosomal DNA in diploid Drosophila melanogaster cells cultured in vitro.

Replication rate and replicon sizes in chromosomal DNA of in vitro cultured diploid D. melanogaster cells were determined using autoradiography of 3H-thymidine labeled DNA. Synthesis of DNA in euchromatic and heterochromatic regions of Drosophila diploid cells occurs at different periods of the S phase which last 10 h. During the first 4 h the synthesis is observed only in euchromatic regions. The heterochromatic synthesis starts shortly before the synthesis in euchromatic regions is completed and lasts for 6 h until the end of the S phase. The cells were synchronized by 5-fluorodeoxyuridine which blocked the diploid cell DNA synthesis. Synthesis was found to start simultaneously in most euchromatic replicons. In the majority of the replicons the synthesis started at a single point and proceeded bidirectionally. The average rate of DNA synthesis per fork was 12.5 mum/h (38kb). The mean distance between the middle points of adjacent labeled regions was 70 mgm (210 kb). The size of most replicons ranged from 40 to 120 mum. - These estimates do not apply to the heterochromatic portions of the D. melanogaster genome since the measurements have been carried out on DNA preparations obtained during the first 2 h of the S phase. - On the average, a replicon can consist of 7 chromomeres since the size of a replicon in diploid cell chromosomal DNA and DNA length of a polytene chromomere average 210 and 30 kb, respectively.

Animals↗
PubMed1977

Isolation of eukaryotic DNA fragments containing structural genes and the adjacent sequences.

In Drosophila melanogaster structural genes are located close to moderately reiterated sequences. One of the clones obtained contains the DNA related to intercalary heterochromatin of D. melanogaster. These are individual differences in the distribution of genetic material in polytenic chromosomes of different stocks of D. melanogaster. The techniques that allow isolation of DNA fragments containing structural genes at the beginning, in the middle, or the end of the coding strand have been elaborated.

Animals↗