Polytene Chromosome Bands Research Articles

Decapentaplegic: A gene complex affecting morphogenesis in Drosophila melanogaster

The decapentaplegic gene complex (2–4.0) in Drosophila melanogaster is defined by a series of allelic mutations affecting imaginal disk development. Decapentaplegic ( dpp) mutant individuals exhibit a variety of pattern deficiencies and duplications in structures derived from one or more of the 15 major imaginal disks. Based on dpp mutant phenotypes, we suggest that the dpp gene complex is involved in the elaboration of positional information within developing epidermal tissue. The dpp mutations are recessive and fall into six phenotypic classes. Milder alleles (classes I and II) affect only one or a few disks while most alleles (classes III, IV, V and EL) affect all major imaginal disks. Class EL homozygotes are embryonic lethals; development is arrested before germ-band shortening late in gastrulation. Presently inseparable from EL, is a haplo-insufficient function ( Hin-d) associated with the distal (left) end of the dpp gene complex. The dpp gene complex occupies most or all of 22F1–3, three densely staining polytene chromosome bands. A colinearity exists between map positions of the four identified functional units within the complex and the severities of mutant phenotypes caused by disruption of these functions. Most dpp mutations are gross chromosomal rearrangements; they exert polar effects on the decapentaplegic functions that are proximal to the rearrangement breakpoints in 22F. Many structural similarities exist between the decapentaplegic and bithorax gene complexes.

Isolation of DNA from single microsurgically excised bands of polytene chromosomes of Chironomus.

A method is described for excising by a glass knife single bands of isolated polytene chromosomes of the salivary glands of Chironomus tentans larvae. DNA strands were isolated from cut-out bands and their contour lengths were determined on electron micrographs. The mean contour length of DNA strands isolated from the double band I-8A was about twice that of the single band I-11B, namely 63 versus 34 micrometers. The described method may be applicable for molecular studies on single bands (e.g., by DNA cloning).

Evolutionary relationships to parasitism by seven species of the Drosophila melanogaster subgroup

Parasitic wasps are an important component of the niche of Drosophila species. The susceptibility to the Cynipid Leptopilina boulardi was estimated in the seven sibling species of Drosophila belonging to the melanogaster subgroup. Three categories of Hies can be distinguished, according to the level of cellular immune reaction and success of parasitism. Drosophila melanogaster and D. mauritiana belong to the category 1, specified by no encapsulative reaction and a high rate of successful parasitism. Category 2, characterized by a moderate encapsulation rate and a high mortality include D. simulans.5, D. erecta and D. orena. Category 3, with D. yakuba and D. tcissien, is specified by a very low rate or absence of successful parasitism due to a highly efficient immune cellular reaction. This classification parallels the phylogenic relationship based upon polytene chromosome banding sequences. Such specific ditferences in susceptibility to parasites may plan an important role in the competition between these species in Africa.

Informational content of polytene chromosome bands and puffs.

(1981). Informational Content of Polytene Chromosome Bands and Puffs. Critical Reviews in Biochemistry: Vol. 11, No. 4, pp. 303-340.

Genetic characterization of the region between 86F1,2 and 87B15 on chromosome 3 of Drosophila melanogaster.

The region between 86F1,2 and 87B15 on chromosome 3 of Drosophila melanogaster, which contains about 27 polytene chromosome bands including the 87A7 heat-shock locus, has been screened for EMS-induced visible and lethal mutations. We have recovered 268 lethal mutations that fall into 25 complementation groups. Cytogenetic localization of the complementation groups by deficiency mapping is consistent with the notion that each band encodes a single genetic function. We have also screened for mutations at the 87A7 heat shock locus, using a chromosome that has only one copy of the gene encoding the 70,000 dalton heat-shock protein (hsp70). No lethal or visible mutations at 87A7 were identified from 10,719 mutagenized chromosomes, and no female-sterile mutations at 87A7 were recovered from the 1,520 chromosomes whose progeny were tested for female fertility. We found no evidence that a functional hsp70 gene is required for development under laboratory conditions.

Isolation and characterization of the dopa decarboxylase gene of Drosophila melanogaster.

We have isolated chromosomal deoxyribonucleic acid clones containing the Drosophila dopa decarboxylase gene. We describe an isolation procedure which can be applied to other nonabundantly expressed Drosophila genes. The dopa decarboxylase gene lies within or very near polytene chromosome band 37C1-2. The gene is interrupted by at least one intron, and the primary mode of regulation is pretranslational. At least two additional sequences hybridized by in vivo ribonucleic acid-derived probes are found within a 35-kilobase region surrounding the gene. The developmental profile of ribonucleic acid transcribed from one of these regions differs from that of the dopa decarboxylase transcript.

Isolation and characterization of the dopa decarboxylase gene of Drosophila melanogaster.

We have isolated chromosomal deoxyribonucleic acid clones containing the Drosophila dopa decarboxylase gene. We describe an isolation procedure which can be applied to other nonabundantly expressed Drosophila genes. The dopa decarboxylase gene lies within or very near polytene chromosome band 37C1-2. The gene is interrupted by at least one intron, and the primary mode of regulation is pretranslational. At least two additional sequences hybridized by in vivo ribonucleic acid-derived probes are found within a 35-kilobase region surrounding the gene. The developmental profile of ribonucleic acid transcribed from one of these regions differs from that of the dopa decarboxylase transcript.

Genetic and biochemical characterization of mutants at an RNA polymerase II locus in D. melanogaster

We previously described an α-amanitin-resistant mutant of D. melanogaster ( AmaC4 or simply C4) with an altered, amanitin-resistant RNA polymerase II. We have now more fully characterized this mutant genetically and biochemically. We genetically mapped C4 to position 35.66 on the X chromosome and cytogenetically localized it to the polytene chromosome band interval 10C2–10D4. We then demonstrated that C4 is allelic to a previously known lethal-mutable locus I(1)L5 in this chromosomal region. Several known lethal alleles of L5 in fact affected the properties of RNA polymerase II in vitro. Following EMS mutagenesis of the C4-bearing chromosome we recovered new lethal L5 alleles, some of which were shown biochemically to have an altered amanitin-resistant polymerase II component. Furthermore, we induced mutants of C4 that had lost amanitin-resistance and showed that these mutants were also lethal alleles of L5. All the lethal alleles of L5 failed to completely complement each other genetically, and when analyzed biochemically their polymerase II displayed altered enzymatic properties. We conclude that C4 is an allele of the L5 locus and that this locus is most probably a structural gene for a subunit of RNA polymerase II. Some of the mutants at this locus display developmental abnormalities.

Cytogenetic analysis of the chromosomal region immediately adjacent to the rosy locus in Drosophila melanogaster.

This report describes the genetic analysis of a region of the third chromosome of Drosophila melanogaster extending from 87D2-4 to 87E12-F1, an interval of 23 or 24 polytene chromosome bands. This region includes the rosy (ry, 3-52.0) locus, carrying the structural information for xanthine dehydrogenase (XDH). We have, in recent years, focused attention on the genetic regulation of the rosy locus and, therefore, wished to ascertain in detail the immediate genetic environment of this locus. Specifically, we question if rosy is a solitary genetic unit or part of a large complex genetic unit encompassing adjacent genes. Our data also provide opportunity to examine further the relationship between euchromatic gene distribution and polytene chromosome structure.----The results of our genetic dissection of the rosy micro-region substantiate the conclusion drawn earlier (SCHALET, KERNAGHAN and CHOVNICK 1964) that the rosy locus is the only gene in this region concerned with XDH activity and that all adjacent genetic units are functionally, as well as spatially, distinct from the rosy gene. Within the rosy micro-region, we observed a close correspondence between the number of complementation groups (21) and the number of polytene chromosome bands (23 or 24). Consideration of this latter observation in conjunction with those of similar studies of other chhromosomal regions supports the hypothesis that each polytene chromosome band corresponds to a single genetic unit.

The genetics of a small autosomal region of Drosophila melanogaster containing the structural gene for alcohol dehydrogenase. I. Characterization of deficiencies and mapping of ADH and visible mutations.

The position of the structural gene coding for alcohol dehydrogenase (ADH) in Drosophila melanogaster has been shown to be within polytene chromosome bands 35B1 and 35B3, most probably within 35B2. The genetic and cytological properties of twelve deficiencies in polytene chromosome region 34--35 have been characterized, eleven of which include Adh. Also mapped cytogenetically are seven other recessive visible mutant loci. Flies heterozygous for overlapping deficiencies that include both the Adh locus and that for the outspread mutant (osp: a recessive wing phenotype) are homozygous viable and show a complete ADH negative phenotype and strong osp phenotype. These deficiencies probably include two polytene chromosome bands, 35B2 and 35B3.

VIABILITY OF HOMOZYGOUS DEFICIENCIES IN SOMATIC CELLS OF DROSOPHILA MELANOGASTER

The viability of cells made homozygous for different deficiencies by induced mitotic recombination was examined. The deficiencies varied in length from two to 30 polytene chromosome bands and were distributed over the five major chromosome arms. Among a sample of 30, ten deficiencies were cell viable. Our results show that 12% of the genome is necessary for cell survival, supporting previous estimates of about 5,000 genes in the genome of Drosophila.

CYTOGENETICS AND EVOLUTION OFSIMULIUM ORNATIPESSKUSE (DIPTERA: SIMULIIDAE). II. TEMPORAL VARIATION IN CHROMOSOMAL POLYMORPHISMS AND HOMOSEQUENTIAL SIBLING SPECIES

The discovery of homosequential species of Hawaiian Drosophila which share identical polytene chromosomes and metaphase karyotypes (Carson et al., 1967), established that overt chromosomal change need not accompany speciation. These homosequential species are morphologically distinct and are, therefore, not sibling species. The genetic divergence that has obviously occurred must therefore have involved only gene mutations. Within the genus Drosophila not all homosequential species, as defined by polytene chromosome banding patterns, share identity of metaphase karyotypes. Thus in the D. pachea group homosequential species show striking heterochromatin differences in their metaphase karyotypes (Ward and Heed, 1970). Since heterochromatic sequences are generally underreplicated relative to euchromatin in polytene chromosomes of Drosophila (Cordeiro et al., 1975; Gall et al., 1974; Rudkin, 1972), no differences in polytene chromosome structure are evident despite the considerable divergence revealed by mitotic karyotypes. Thus where possible, analysis of both diploid and polytene chromosomes should be carried out. In the Simuliidae mitotic karyotypes are remarkably conservative being identical in species of several different genera (Rothfels, 1956). On the other hand, the analysis of polytene chromosomes has shown the existence of sibling species

Distribution and Evolution of Q-Bands in the Polytene Chromosomes of the Virilis Group

SUMMARYQuinacrine-bright bands of polytene chromosomes have been localized in the members of the virilis group. Four species: Drosophila virilis, D. lummei, D. flavomontana and D. ovivororum have Q-bands of varying intensities. D. virilis, the most karyotypically primitive member of the group, has a Q-band doublet in the heterochromatin of chromosome four. This doublet is not found in any of the other members of the group. One species, D. flavomontana, is polymorphic for a Q-band in the Yi-j region of chromosome four. With the exception of D. ezoana, chromocentric quinacrine-bright granules are a unifying feature of all the members of the virilis group.

CYTOGENETIC ANALYSIS OF CHROMOSOME 3 IN DROSOPHILA MELANOGASTER: ISOLATION AND CHARACTERIZATION OF FOUR NEW ALLELES OF THE PROBOSCIPEDIA (pb) LOCUS

Previous studies on proximal 3R have cytologically localized the dominant homeotic loci Antennapedia (Antp), Multiple Sex Comb (Msc), Nasobemia (Ns), and Extra Sex Comb (Scx). In this study we set out to find the site of the proboscipedia (pb) locus. In order to accomplish this, four new alleles of this homeotic gene were induced with gamma rays. Genetic and cytogenetic analyses have shown that the pb locus resides in polytene chromosome bands 84A1-6, immediately adjacent to the Antp gene complex in 84B1-2. An analysis of the morphology of the proboscis and the dose relationships of the four new alleles have shown that this homeosis is unusual in at least two respects. First, the two different developmental fates realized in the proboscis at 18 degrees (labial palps --> arista) and 29 degrees (labial palps --> leg) under the influence of pb(1) grown at 18 degrees , while the remaining three are like pb(1) at 29 degrees . Dosage studies reveal that this difference reflects a hypomorphic vs. amorphic condition. Second, like the original, these new alleles produce a prothoracic rather than a mesothoracic leg in the proboscis. Both of these results indicate that pb is unique among the homeotics, and as such it may offer some new insights into developmental processes.

NONESSENTIAL SEQUENCES, GENES, AND THE POLYTENE CHROMOSOME BANDS OF DROSOPHILA MELANOGASTER

From earlier work, there appears to be an underlying one-to-one correspondence of polytene chromosome bands and complementation groups within a sizeable, continuous X-chromosome segment, 3A1-3C7 ( Judd, Shen and Kaufman 1972; Lefevre and Green 1972). However, most of the data supporting this one-to-one relation of bands and genes were gathered from mutants that upset vital functional units, thus leading to lethality. Among this series of mutants, only four loci, zeste, white, roughest and verticals, have no known lethal alleles. If phenotypic changes less drastic than lethality result from the loss of other chromosomal segments, they probably would not have been recognized in the earlier studies.-We report here some chromosomal sequences localized in 3A, 3B, and 3C whose loss effects no lethal change in the development of the animal. A portion of the 3A3-3A4 region can be disrupted in a nonlethal fashion, yet this sequence does not seem to be a part of either the zeste locus or l(1)zw1, which are known to be located in these bands. Two more complementation groups have been discovered that have no lethal alleles and map to 3B4-3B6; a third falls within 3B1-2. The loss of a sequence in 3C2-3 is tolerated without any genetically observable effect. Between 3C7 and the boundary of 3D there is at least one more sequence that behaves in this manner.-The discovery of these units, which are not allelic to any of the loci previously known, makes it clear that division 3B contains more genes (i.e., complementation groups) than polytene chromosome bands, while portions of 3A and 3C seem to have no functional significance. Accordingly many polytene chromosome bands may be composites of several complementing functional units. This investigation also indicates that there are chromosomal segments that are seemingly dispensible and thus function in a manner that is difficult or impossible to define with available methods.

Messenger RNA for the insect storage protein calliphorin: in vitro translation and chromosomal hybridization analyses of a 20 S poly(A)-RNA fraction.

A major poly(A)-containing RNA fraction of the approximate size expected of a monocistronic mRNA for the storage protein calliphorin has been isolated from the larval fat bodies of Calliphora vicina during early instar 3. This 20 S RNA fraction programs the synthesis by cell-free wheat embryo extracts of polypeptides of 86,000 daltons identified by tryptic peptide fingerprinting as precursors of the authentic calliphorin subunits of 83,000 daltons. Complementary DNA synthesized by AMV reverse transcriptase using the same 20 S RNA as template hybridized in situ to a single segment of one or two bands in the salivary polytene chromosomes of C. vicina.

Drosophila: the genetics of two major larval proteins

A series of irradiation-induced deficiencies covering 62 polytene chromosome bands in chromosome arm 3L of Drosophila melanogaster includes the loci of two abundant developmentally regulated larval proteins. The structural gene for larval serum protein 2 (LSP 2) lies at 68E3 or 4, and that for salivary glue secretion protein 3 between 68A8 and 68C11, coincident with a major intermoult puff active in the salivary gland at the time of glue synthesis. The structural genes for esterase 6 and four visible recessive loci lie within the same region.

Fluorescence polarization of stretched polytene chromosomes stained with acridine orange.

The molecules of the fluorescent dye acridine orange (AO) bind to DNA in such a way that the absorption and emission dipoles lie on a plane perpendicular to the DNA axis. For this reason, definite fluorescence polarization should correspond to each mode of spatial DNA packing. A chromosome, considered as an axially symmetrical ensemble of DNA, was characterized by two experimental parameters, P parallel and P perpendicular, i.e., by polarizations of fluorescence excited by light polarized parallel and perpendicular to the symmetry axis. In view of the sequential order in the packing levels of DNA fiber in a chromosome, it was suggested that, under mechanical stretching, the highest level is disrupted first, then the others, in the order of their sequence. Isolated chromosomes of Chironomus thummi were stained with AO and stretched with needles of a micromanipulator. From the changes of P parallel and P perpendicular measured during stretching it was concluded the polytene chromosome bands have three, at least, DNA packing levels, tentatively described as 100 A fiber, 250 A coil and chromomere.

Cytological evidence of male heterogamety in sex determination of Telmatoscopus albipunctatus (Diptera: Psychodidae).

Telmatoscopus albipunctatus is polymorphic for several polytene chromosome bands. In examining the inheritance of a polymorphic heterochromatin-like band in chromosome IV we verified that it is inherited like a sex-linked factor. There are two types of chromosome IV in regard to this band: one bears a very thick heterochromatin-like band (H+), and the other bears a thinner corresponding band (H-). Three kinds of combinations are found in our stocks: H+H+, H+H- and H-H-. All three combinations can be found in females; however, in males, only the combinations H+H- and H-H- are found. Through specific crosses, it was concluded that the sex determining factor is located in chromosome IV in close vicinity to these bands.

Differential staining of polytene chromosome bands in Chironomus by Giemsa banding methods

Two Giemsa banding methods (C banding and RB banding) are described which selectively stain the centromere bands of polytene salivary gland chromosomes in a number of Chironomus species. - By the C banding method the polytene chromosome appearance is changed grossly. Chromosome bands, as far as they are identifiable, are stained pale with the exception of the centromere bands and in some cases telomeres, which then are intensely stained reddish blue. - By the RB method the centromere bands are stained bright blue, whereas the remainder of the polytene bands stain red to red-violet. - Contrary to all other species examined, in Chironomus th. thummi numerous interstitial polytene chromosome bands, in addition to the centromere regions, are positively C banded and blue stained by RB banding. In the hybrid of Ch. th. thummi X Ch. th. piger only those interstitial thummi bands which are known to have a greater DNA content than their homologous piger bands are C banding positive and blue stained by the RB method whereas the homologous piger bands are C banding negative and red stained by RB banding. Ch. thummi and piger bands with an equal amount of DNA both show no C banding and stain red by RB banding. - It seems that the Giemsa banding methods used are capable of demonstrating, in addition to centromeric heterochromatin, heterochromatin in those interstitial polytene chromosome bands whose DNA content has been increased during chromosome evolution.