Salivary Chromosome Map Research Articles

Cytogenetical localization of the amylase region in Drosophila melanogaster by means of translocations.

Applying the translocation stocks T(2; 3) 108, T(1;2) OR 72 and T(1; 2) OR 32 it was found that flies hyperploid for the translocated sections are also hyperploid for the Amylase region. On the salivary chromosome map the amylase genes are therefore placed to the right of section 54B. An amylase gene transposed to heterochromatin by the translocation T(1;2) OR 32 with its breakpoint at 54A exhibits position-effect variegation. The amylase genes are therefore located between sections 54B and 55 on the salivary chromosome map.

Salivary chromosome analysis of aberrations.

Even with the advent of sequenced genomes, the ability to locate aberration breakpoints onto the salivary chromosome map remains one of the singular strengths of Drosophila as a research organism. Salivary chromosome analysis is not difficult, yet many people are reluctant to attempt to do it: and if they do begin they may flounder for lack of a clear idea of what they should be trying to do. I hope this chapter will both encourage more people to try and also make the learning easier. Once mastered, doing salivary cytology is fun and rewarding: and you will never again have your research set back 6 mo because the “deficiency” stock someone sent you was not what it was supposed to be; as a matter of course you will have checked it out first!

An inversion within the subterminal inversion inDrosophila ananassae

An inversion within the subterminal inversion in 2L ofDrosophila ananassae has been detected in a laboratory strain originating from Kuala Lumpur, Malaysia. The break points of inversion have been located in the reference map of salivary chromosomes. The data on the frequencies of different karyotypes indicate that inversion heterozygotes exhibit heterosis.

Mutation in a testis-specific beta-tubulin in Drosophila: analysis of its effects on meiosis and map location of the gene.

The structural gene for a testis-specific beta--tubulin subunit in Drosophila melanogaster was mapped genetically and cytogenetically by means of a dominant male sterile mutation, B2tD, in which a variant form of the testis beta--tubulin is expressed. The B2t locus is at 48.5 map units on the third chromosome genetic map, and in bands 85D4-7 on the salivary chromosome map. The mutation B2tD causes disruption of microtubule function in all stages of spermatogenesis, beginning with meiosis. The effects of gene dosage of B2tD on meiosis were examined in detail cytologically at the light microscope level. In testes of flies in which the variant tubulin subunit is expressed, abnormal meiotic spindle formation, improper chromosome movement and failure to undergo cytokinesis occur. The extent of these defects in microtubule function depends on the dosage of the B2tD mutation, being most severe in males homozygous for the mutation, intermediate in males heterozygous for the mutation, and least marked in males heterozygous for B2tD and a tandem duplication of the region of the genome containing the B2t locus. Chromosomal events unrelated to microtubule function, such as replication and condensation, occur normally. Results obtained during mapping of the B2t locus strongly suggest a haplo-insufficient site at or closely linked to this locus.

ON THE COMPONENTS OF SEGREGATION DISTORTION IN DROSOPHILA MELANOGASTER

The segregation distorter (SD) complex is a naturally occurring meiotic drive system with the property that males heterozygous for an SD-bearing chromosome 2 and an SD(+)-bearing homolog transmit the SD-bearing chromosome almost exclusively. This distorted segregation is the consequence of an induced dysfunction of those sperm that receive the SD(+) homolog. From previous studies, two loci have been implicated in this phenomenon: the Sd locus which is required to produce distortion, and the Responder (Rsp) locus that is the site at which Sd acts. There are two allelic alternatives of Rsp-sensitive (Rsp(sens)) and insensitive (Rsp(ins)); a chromosome carrying Rsp(ins) is not distorted by SD. In the present study, the function and location of each of these elements was examined by a genetic and cytological characterization of X-ray-induced mutations at each locus. The results indicate the following: (1) the Rsp locus is located in the proximal heterochromatin of 2R; (2) a deletion for the Rsp locus renders a chromosome insensitive to distortion; (3) the Sd locus is located to the left of pr (2-54.5), in the region from 37D2-D7 to 38A6-B2 of the salivary chromosome map; (4) an SD chromosome deleted for Sd loses its ability to distort; (5) there is another important component of the SD system, E(SD), in or near the proximal heterochromatin of 2L, that behaves as a strong enhancer of distortion. The results of these studies allow a reinterpretation of results from earlier analyses of the SD system and serve to limit the possible mechanisms to account for segregation distortion.

The Salivary Chromosomes of <i>Anopheles philippinensis</i> Ludlow

A standard salivary chromosome map for Anopheles (Cellia) philippinensis has been constructed and presented. A comparison of the banding pattern in the salivary chromosomes of A. philippinensis with those already investigated elsewhere has been made. A few characters in the band sequence have been observed to exist in almost all the species of the subgenus Cellia, thus, reflecting a possible evolution of various species from a common ancestral form.

Cytological localization of the maternal effect gene, tuh-1, in Drosophila melanogaster.

The sex-linked gene, tuh-1, produces a maternal effect that is associated with the tumorous head abnormality in Drosophila melanogaster. With the aid of various known deletions, tuh-1 has been localized to band 20A1-2 on the salivary chromosome map of the X.

Karyotype and salivary chromosomes of Drosophila latifshahi Gupta & Ray-Chaudhuri

Mitotic and salivary chromosomes of D. lati/shahi have been examined. A standard map of salivary chromosomes after comparing them in seven different larvae has also been prepared. Important identifiable natural landmarks in each chromosome arm are recognizable. A small basal inversion has been found in the left arm of the 3rd chromosome.

Intergroup phylogenies in Drosophila as determined by comparisons of salivary banding patterns.

A salivary gland chromosome phylogeny is presented which summarizes the evolutionary relationships of twenty-two species belonging to the sub-genus Drosophila, and members of the twelve species groups: D. melanica, D. repleta, D. carbonaria, D. polychaeta, D. annulimana, D. robusta, D. carsoni, D. virilis, D. funebris and the "picture-wing," D. mimica and D. crassifemur groups (of Hawaii).-Photographic salivary chromosome maps were prepared for all twenty-two species studied. While the chromosomes of different species belonging to the same group can usually be homologized almost completely, so that construction of intragroup phylogenies is easy, chromosomes of members of different groups are so modified structurally that in most cases only short sections can be fully homologized, and these in only one or two chromosome elements.-Broadly homologous chromosome elements were compared for three species at a time, and on the basis of overlapping homologous sections, or overlapping inversions included within homologous sections, the trio of chromosomes, and the species to which they belonged can often be arranged in a two-step phylogenetic series. Detection of many such ordered trios permits construction of a single phylogenetic scheme encompassing all species.-D. nigromelanica, of the D. melanica group is found to be chromosomally intermediate between the rest of its group and the species belonging to other groups, suggesting that it is the most nearly ancestral member of its group. When trios of species including D. nigromelanica and members of two other species groups are compared, it is found that in twelve of fourteen such comparisons the chromosomes of D. nigromelanica are structurally intermediate between those of the members of the other two species groups, indicating the central position of D. nigromelanica in the phylogeny as a whole.-Available cytological evidence indicates that among the nine continental groups studied, it is the D. robusta group which is chromosomally closest to the Hawaiian "picture-wing" groups. Among the members of the Hawaiian groups it is D. primaeva and D. attigua which are found to be closest to the continental species. This finding tends to confirm the earlier conclusion of Carson and Stalker, based on different evidence, that the above two species were in an ancestral position in the Hawaiian phylogeny.-The relationship of the D. robusta and D. melanica groups demonstrated in this paper, the phylogenies within each of these two groups earlier worked out by Narayanan and by Stalker, and the present geographical distributions of the species within them, require that at least three Asiatic-New World migrations must have occurred during the evolution of the two groups.

Cytogenetics of natural populations of Drosophila

D. bipectinata and D. malerkotliana differ from each other by three overlapping inversions in IIL, two included inversions in IIIL and two overlapping inversions in IIIR. These inversions were analysed on the basis of the salivary chromosome maps of D. malerkotliana. Bock's (1971) data revealed that the four members of the bipectinata species complex differ from each other with respect to overlapping inversions. The reason why the ancestral population which may have been heterozygous for common inversions split into at least four groups, each leading to the formation of a new species, and the possible mechanism of the origin of sexual isolation between the groups is discussed.

Amylase variants in Drosophila melanogaster: linkage studies and characterization of enzyme extracts.

AbstractThe amylases of D. melanogaster were characterized by several parameters. Starch‐iodine and 3,5‐dinitrosalicylic acid reduction methods were employed to determine activity. Conditions were defined under which activity, in crude aqueous extracts could be restricted to α‐amylase(s) of fly origin. Biochemical properties of the α‐amylases from eleven homozygous Amy strains were found to be very similar in temperature stability, pH optimum, substrate specificity and the effects of various activators and inhibitors. All were activated by chloride ions and showed a pH optimum of about 7.4. Relative efficiencies on several substrates were tested: soluble starch, amylopectin, β‐limit dextrins, glycogen and amylose. EDTA completely inhibited all extracts, presumably by the removal of calcium required for activation. The specific α‐amylase inhibitor from wheat grain also completely inhibited activity, as did reduced glutathione. PCMB had no discernible effects on activity.Eight of the 11 strains tested are known to produce different electrophoretic banding patterns for amylases. The total maximum activity of each strain may also be used to characterize it and, accordingly, three strains with amylases of the same electrophoretic mobility were distinguished by differences in their specific activities. Sexual dimorphism in amylase activity was defined, as well as activity in heterozygotes between strains. Aside from the distinctions between strains already noted, four strains differed in their relative susceptibility to heat and to α‐amylase inhibitor.Linkage experiments indicated that the Amy region lies at 77.3 on the genetic map of the second chromosome and to the right, but near, section 52F on the salivary chromosome map.

The salivary chromosomes of Anopheles stephensi stephensi.

A salivary chromosome map of Anopheles (Cellia) stephensi stephensi is presented. The chromosomes exist as 5 units, the telocentric X chromosome and 2 metacentric autosomes. Chromosome 2 has arms of unequal lengths. Chromosome 3 has arms of equal lengths. The banding pattern is similar to that of Anopheles gambiae (subgenus Cellia ) but dissimilar to the species of the subgenera Anopheles and Nyssorhynchus thus far studied.

STUDIES ON PUFFING IN THE SALIVARY GLAND CHROMOSOMES OF <i>DROSOPHILA ANANASSAE</i>

1) Puffing patterns in the salivary gland chromosomes of Drosophila ananassae have been investigated.2) The salivary chromosome map of this species was reconstructed.3) Puffs were found 48 regions of a total of 6 elements of the salivary chromosomes during the 3rd instar and prepupal stages. Among these, 16 regions of the 2-chromosome were selected to observe changes in the puffing pattern through the developmental stages of this organism.4) Comparison of the puffing patterns was made among three different karyotypes, AA, BB, and AB, derived from a subterminal inversion, In2L.5) The appearance of puffs was found to be correlated with the rates of development of the three types, which varied in the relation AB=BB>AA.6) No puff that was unique to any of the three karyotypes has been observed. Rather, in almost all regions the puff patterns of the three types were found to be similar with respect to both their correlation with the stages of development and their continuance.

Genetical Relationship and Isolating Mechanisms in the Species SubgroupAnanassae(Sophophora, Drosophila) VI. Interspecific Cytological Divergence in the Three Species of theAnanassaeSpecies Subgroup

SUMMARYThe chromosome complement of D. bipectinata and D. malerkotliana comprises four pairs of V-shaped elements, two of which are large, one medium and one small. The karyotype of D. ananassae differs from those of D. bipectinata and D. malerkotliana with respect to one member of the medium pair of Vs, which is replaced by a J-shaped element. The X chromosome is represented by a medium V-shaped element in all the three species. Whereas the Y chromosome is morphologically indistinguishable from the X in D. bipectinata and D. malerkotliana, it is represented by a J-shaped element in D. ananassae.An analysis of the salivary chromosomes of the hybrid between D. bipectinata and D. malerkotliana indicates that the difference in the chromosomes of these two species lies in two inversion complexes one of which is in II L and the other in III R. The direct comparison of the band pattern in the salivary chromosome maps of D. ananassae and D. bipectinata reveals that six inversions, one translocation and a few transpositions mark the cytological difference between the two species.

The salivary chromosomes of Anopheles vestitipennis.

A standard salivary chromosome map is presented for Anopheles vestitipennis, based upon a population collected in the state of Vera Cruz, Mexico. It is proposed that this serves as the “standard” map for this species. Certain similarities of banding pattern, particularly at the ends of the autosomes, are evident between vestitipennis and the Holarctic Maculipennis species.

A Viable Homozygous Deficiency in Drosophila melanogaster

THROUGH combination of fragments of chromosomes from two complicated rearrangements (obtained in my work dealing with the wmt position effect, 1938, in the press), one of which causes a light wmt and the other a very dark wmt eye colour, the first having the break to the left and the other to the right of the w gene, a stock was obtained which had no w gene in its genotype. Since the cytological observations show that the breaks occur near each other, or even at the same point in both the original aberrations, it was concluded that only one gene, namely, the gene white, was deficient. The cytological data agree Well with the phenotypical actions of the w deficiency, which does not differ from a simple w mutation, causing the white eye colour. The cytological observations agree also with the data obtained by numerous authors showing the position of the w gene in the 3C2 region of Bridges' salivary chromosome map. But in the w deficiency combinations the 3C2 band is not thinner than in the normal chromosome.

SALIVARY CHROMOSOME MAPS

Journal Article SALIVARY CHROMOSOME MAPS: With a Key to the Banding of the Chromosomes of Drosophila Melanogaster Get access CALVIN B. BRIDGES CALVIN B. BRIDGES Carnegie Institution of Washington, Resident at California Institute of TechnologyPasadena, California Search for other works by this author on: Oxford Academic PubMed Google Scholar Journal of Heredity, Volume 26, Issue 2, February 1935, Pages 60–64, https://doi.org/10.1093/oxfordjournals.jhered.a104022 Published: 01 February 1935