A Guide to the Russian Academy of Sciences - University of Texas ...

Tchurikov, Ponomarenko, Proc. Natl. Acad. Sci., 89, 6751-6755, 1992). The
domains were observed after spontaneous degradation of chromosomes upon cell
death in the low melt agarose blocks. To elucidate the nature of forum-domains we
have started studying the Drosophila DNA big segment containing the cut locus.
The iunction of two neighboring domains was mapped in the central part of the
locus. Each domain is more that 100 kb in length. Partial sequencing of the 12 kb
region were DNA is attacked during spontaneous degradation of chromosomes was
performed. Similarly, the iunction of two forum-domains in an anonymous
genomic region was mapped and sequenced. To characterize domains further we
suppose to map looped domains, repetitive and transcribed sequences in these
genomic regions. The role of retroelements in evolution The study of suffix
retroposon in Drosophila genome continued. Most suffix copies are independent
and rather conservative, whereas the others are incorporated in different Drosophila
genes. In the latter case the suffix forms the last exon as in mature mRNA, iust
before poly(A) stretch ( that is why the element was denoted as suffix, Tchurikov et
al., Cell 28, 365-373,1982). Analysis of the suffix in different genes allows us to
conclude that the element occurs in one and the same orientation and is involved in
maturation of 3' domain of different mRNAs, thus specifying precise excision,
splicing, and polyadenylation (Tchurikov et al., EMBO I.,9, 2341-2347, 1986).
So, suffix presents the only known example of mobile element with known cellular
function. That is why it was attractive for us to study evolution of its sequences
using computer search of current nucleotide data bases. We observed the homology
between the central domain from plus strand of the element and 16S ribosomal
RNA stretches in a group of b acteria. These bacteria have close association with
eukaryotic cells and are capable of growing only inside eukaryotic cells ( so-called
endosymbionts). They are mainly associated with arthropods or other invertebrate
hosts. The data suggest the origin of this domain of the suffix from DNA or RNA
sequences of microbial organism by horizontal transfer. The suffix was found to
appear in opposite polarity comparing with the coding sequence in F and DOC
Drosophila retroelements, specifying the reverse transcriptase C-domain and
supplying the elements with both stop codon and polyadenylation signal. Thus, the
suffix incorporates an ancient domain and in different orientations it functions as a
regulatory or coding sequence in the nuclei and cytoplasm. The data on evolution of
this retroelement are clearly inconsistent with the selfish DNA paradigm. Really, the
retroelements may suit as the material for genome evolution.
1997 update: CYTOMETRY AND CHROMOSOME ISOLATION
Head Andrei I. Poletaev, Ph.D.
The work of the Unit was focused on the problems of human genome studies at the
chromosomal level. These problems can be formulated as "chromosomometry".
During the past few years the works on quantitative analysis of human
chromosomes (Kravatskii, Poletaev, Molekularnaya Biologiya, 28, 887-899, 1994;
Kravatskii, Kuznetsova, Nasedkina, Poletaev, Molekularnaya Biologiya, 30, 192-
208, 1996) by laser flow cytometry have been carried out. The experimental results
(flow karyotypes) obtained along with the developed procedures of computer data
analysis can reveal small differences in chromosomes size (0.3-0.5%, 200-500 kb),
that cannot be achieved by other methods. Such quantitative analysis of karyotypes
makes it possible to get the highest accuracy in determination of the size of
chromosomes and to trace the minimal structural rearrangement in karyotype. The
elaboration of a new technology for investigation of human chromosomes, "the
cell-by-cell flow analysis of chromosome sets" is under way. Unlike traditional
studies of metaphase chromosomes suspensions obtained from millions of mitotic
cells, the principal features of the approach are based on the preparation of mitotic
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