Showing papers on "Chromosome published in 1980"
TL;DR: The sequence data suggest that intergenic conversions occur in the germ line, and strongly suggest that DNA sequence polymorphisms for localized deletions, additions and base substitutions are very common in human populations.
810 citations
TL;DR: The centromeric DNA (CEN3) from yeast chromosome III has been isolated on a 1.6 kilobase-pair segment of DNA located near the centromere-linked CDC10 locus of Saccharomyces cerevisiae.
Abstract: The centromeric DNA (CEN3) from yeast chromosome III has been isolated on a 1.6 kilobase-pair segment of DNA located near the centromere-linked CDC10 locus of Saccharomyces cerevisiae. When present on a plasmid carrying a yeast chromosomal replicator, CEN3 enables that plasmid to function as a chromosome both mitotically and meiotically. Minichromosomes containing CEN3 are stable in mitosis and segregate as ordinary yeast chromosomes in the first and second meiotic divisions.
716 citations
TL;DR: The autoantibody was present in high frequency in the calcinosis/Raynaud's phenomenon/esophageal dysmotility/sclerodactyly/telangiectasia variant of scleroderma and appeared to be a protein or polypeptide tightly bound to DNA.
Abstract: Sera from patients with scleroderma contained several autoantibodies to nuclear antigens which were distinguished by different patterns of nuclear immunofluorescence staining. One of these autoantibodies reacted with centromeric regions of chromosomes. In chromosome spreads, the staining appeared as two small spheres at the centromere, resembling kinetochores. The antigenic determinant appeared to be a protein or polypeptide tightly bound to DNA. The autoantibody was reactive with centromeres of cells derived from humans, mice, and Chinese hamsters. The autoantibody was present in high frequency in the calcinosis/Raynaud's phenomenon/esophageal dysmotility/sclerodactyly/telangiectasia variant (CREST) of scleroderma.
689 citations
TL;DR: The only factor found to be unequivocally associated with the aetiology of chromosome abnormalities in spontaneous abortions was increasing maternal age in trisomies.
Abstract: Cytogenetic analysis of 1000 spontaneous abortions showed 463 to have an abnormal chromosome constitution. The proportion of chromosome abnormalities varied with the gestational age of the abortus and the type of tissue cultured but was not significantly different among the five racial groups represented in the study population. It was suggested that differences in the rate of chromosome abnormalities among cytogenetic studies of spontaneous abortions were the result of methodological differences in sample selection rather than real biological variation among study populations. The only factor found to be unequivocally associated with the aetiology of chromosome abnormalities in spontaneous abortions was increasing maternal age in trisomies.
627 citations
TL;DR: A cytogenetic study performed on a population of the South American leptodactylid frog Eleutherodactylus maussi revealed multiple sex chromosomes of the X1X1X2X2♀/X1 X2Y♂ (=XXAA/XXAY♂) type, which is interpreted as the ancestral condition, preceding the occurrence of the Y-autosome fusion.
Abstract: Highly differentiated heteromorphic sex chromosomes were found in the karyotypes of Pyxicephalus adspersus (= Rana adspersa) and analysed with the various banding methods. The W chromosome is considerably smaller than the Z chromosome and consists to a great proportion of constitutive heterochromatin. The chromosome lengths and the DNA content of this species have the lowest values determined in the Ranidae to date. The nucleolus organizer regions in the chromosomes reveal a high frequency of inter-individual variations (duplications, triplications) and aberrations. In one female animal, a translocation between the W chromosome and a nucleolus organizer was identified. Preliminary results indicate, that the same chromosome pair which in P. adspersus constitutes the heteromorphic sex chromosomes is still in an initial stage of morphological differentiation in P. delalandii. Although the ZZ/ZW sex chromosomes in Pyxicephalus have developed independently of the ZZ/ZW sex chromosomes in birds and reptiles, they seemed to have passed through identical stages of morphological differentiation. In this process, the heterochromatinization of the W chromosome had a decisive function.
498 citations
TL;DR: The analysis of the 5S RNA genes emphasizes the homoeology between chromosomes 1B of wheat and 1R of rye since both have these genes in the same position relative to the secondary constriction.
Abstract: The chromosomal locations of ribosomal DNA in wheat, rye and barley have been determined by in situ hybridization using high specific activity 125I-rRNA. The 18S-5.8S-26S rRNA gene repeat units in hexaploid wheat (cv. Chinese Spring) are on chromosomes 1B, 6B and 5D. In rye (cv. Imperial) the repeat units occur at a single site on chromosome 1R(E), while in barley (cv. Clipper) they are on both the chromosomes (6 and 7) which show secondary constrictions. In wheat and rye the major 5S RNA gene sites are close to the cytological secondary constrictions where the 18S-5.8S-26S repeating units are found, but in barley the site is on a chromosome not carrying the other rDNA sequences. — Restriction enzyme and R-loop analyses showed the 18S-5.8S-26S repeating units to be approximately 9.5 kb long in wheat, 9.0 kb in rye and barley to have two repeat lengths of 9.5 kb and 10 kb. Electron microscopic and restriction enzyme data suggest that the two barley forms may not be interpersed. Digestion with EcoR1 gave similar patterns in the three species, with a single site in the 26S gene. Bam H1 digestion detected heterogeneity in the spacer regions of the two different repeats in barley, while in rye and wheat heterogeneity was shown within the 26S coding sequence by an absence of an effective Bam H1 site in some repeat units. EcoR1 and Bam H1 restriction sites have been mapped in each species. — The repeat unit of the 5S RNA genes was approximately 0.5 kb in wheat and rye and heterogeneity was evident. The analysis of the 5S RNA genes emphasizes the homoeology between chromosomes 1B of wheat and 1R of rye since both have these genes in the same position relative to the secondary constriction. In barley we did not find a dominant monomer repeat unit for the 5S genes.
281 citations
TL;DR: This hereditary disease is shown to be the result of a deletion of at least 40,000 base pairs of the γδβ -globin gene locus, which results in a severe anaemia in newborns which subsequently develops into a β-thalassaemia syndrome in adult life.
Abstract: In gamma-beta-thalassaemia, human gamma- and beta-globin gene expression is suppressed; this results in a severe anaemia in newborns which subsequently develops into a beta-thalassaemia syndrome in adult life. This hereditary disease is now shown to be the result of a deletion of at least 40,000 base pairs of the gammadeltabeta-globin gene locus. The gamma- and delta-globin genes are deleted in the affected chromosome but, surprisingly, the beta-globin gene is still present, together with a large segment of the DNA sequences flanking the gene on its 5'-side and the entire region on the 3'-side of the gene. Hence, a deletion of DNA far from the beta-globin gene results in the suppression of its activity.
163 citations
Journal Article•
TL;DR: Trypsin G banding was performed on metaphase chromosomes from 14 cell lines derived from primary tumors or metastases of 11 patients with testicular cancer, finding consistent involvement of chromosome 1 in aberrations may be associated with the highly malignant nature of testicular cancers.
Abstract: Trypsin G banding was performed on metaphase chromosomes from 14 cell lines derived from primary tumors or metastases of 11 patients with testicular cancer Most of the cell lines, 11 of 14, have a modal number between 51 and 61 All lines have numerical and structural changes involving chromosome 1 with trisomy of the q arm being the common aberration Break points in chromosome 1 were nonrandom, being concentrated in the regions of p12, q12, p36, and p22, which resulted in morphologically identical marker chromosomes in different cases These changes probably are not artifacts of cell culture In one instance, three lines derived from the same patient, one from tissue removed at operation, and two from separate metastases removed at autopsy nearly 3 years later after unsuccessful radiotherapy and chemotherapy had identical chromosome compositions In another case, lines derived from a primary tumor and a metastasis from the same patient also had identical marker chromosomes The consistent involvement of chromosome 1 in aberrations may be associated with the highly malignant nature of testicular cancers
160 citations
TL;DR: The results and the lack of strong correlations between the genetic effects on the activities of different enzymes indicate that the effects are mainly specific for individual enzymes.
Abstract: The genetic component of variation of enzyme activity in natural populations of Drosophila melanogaster was investigated by using two sets of chromosome substitution lines. The constitution of a line of each type is: i1/i1;+2/ +2;i3/i3 and i1/i1;i2/ i2;+3/+3, where i refers to a chromosome from a highly inbred line and + refers to a chromosome from a natural population. The + but not the i chromosomes vary within a set of lines. By use of a randomized block design to test and estimate components of variance, 50 of the second- and 50 of the third- chromosome substitution lines have been screened for variation in the activity levels of seven enzymes. Six of the seven enzymes show a significant genetic component in at least one set of lines, and five of the seven enzymes show activity variations attributable to factors that are not linked to the structural gene. These unlinked activity modifiers identify possible regulatory elements. Analyses of covariance show that most of the genetic variation of enzyme activities cannot be accounted for by genetic variation of live weight or protein content. These results and the lack of strong correlations between the genetic effects on the activities of different enzymes indicate that the effects are mainly specific for individual enzymes.
158 citations
TL;DR: In this paper, satellite DNA sequences have become distributed along the length of the W and resulted in morphological differentiation of sex chromosomes, which strongly suggests that functional constraints may have limited sequence divergence.
Abstract: Satellites visible in female but not in male DNA were isolated from the snakesElaphe radiata (satellite IV, p = 1.708 g · cm−3) andBungarus fasciatus (BK1 minor, p=1.709 g · cm−3). The satellites cross hybridize. Hybridization of3H labelled nick translated BK minor satellite DNA with the total male and female DNA and/or chromosomes in situ of different species of snakes revealed that its sequences are conserved throughout the snake group and are mainly concentrated on the W chromosome. Snakes lacking sex chromosomes do possess related sequences but there is no sex difference and visible related satellites are absent. The following conclusions have been reached on the basis of these results. 1. The W chromosome associated satellite DNA is related to similar sequences scattered in the genome. 2. The origin and increment in the number of the W satellite DNA sequence on the W chromosome is associated with the heterochromatinization of the W. 3. Satellite sequences have become distributed along the length of the W and resulted in morphological differentiation of sex chromosomes. 4. Evolutionary conservation of W satellite DNA strongly suggests that functional constraints may have limited sequence divergence.
157 citations
TL;DR: The present work presents a meta-analysis of yeast chromosomol genes that highlights the importance of knowing the carrier and removal status of canine coronavirus, as a source of infection for other animals.
Abstract: PROSPECTIVES AND SUMMARY 845 GENETIC ANALYSIS IN yEAST 846 Tetrad Analysis 846 New Advances in Genetic Analysis 850 Construction of recombinant DNA molecules 850 Identification of cloned genes 850 Yeast transformation 854 ORGANIZATION AND REPLICATION OF THE YEAST CHROMOSOMES 856 Chromosome Structure 858 Chromosome Replication 860 Structure of replicating nuclear DNA molecules 860 Control of DNA synthesis 862 Yeast DNA polymerases .. ... ... ........ ... ..... 864 ANALYSIS OF SPECIFIC CLASSES OF CHROMOSOMAL GENES 864 Structural Analysis of Single-Copy Genes 865 Repeating Chromosomal Genes 866 Yeast ribosomal DNA genes 866 Structure of yeast tRNA genes 867 Other repeating yeast chromosomol genes 868 STRUCTURE AND REPLICATION OF THE 2p.m PLASMIDS 869 CONCLUSIONS AND FUTURE PROSPECTS 871
TL;DR: In a limited genetic analysis, the determinants of restriction and modification did not recombine with each other, and since there was no reassortment of these phenotypes among the parental output of crosses it appeared that the determinant were located close together on the chromosome.
Abstract: SUMMARY: Streptomyces albus G mutants (at least 12 of which were independent) defective in SalGI-mediated restriction (R-) were isolated after mutagenesis. Some of them lacked detectable SalGI activity in cell-free extracts. Some were also partially or completely defective in SalGI-associated modification (M-). Loss of restriction rendered S. albus G sensitive to many phages to which it was normally totally resistant. DNA from one such phage had many SalGI target sites (mean, one site per 1.35 kilobases). A mutant was isolated which was heat-sensitive for growth, apparently because it was restriction-proficient but temperature-sensitive for modification. At a rather high frequency, this mutant generated spontaneous heat-tolerant derivatives which were nearly all R-. Such R- mutants were always M- rather than being temperature-sensitive for modification. In a limited genetic analysis, the determinants of restriction and modification did not recombine with each other, and since there was no reassortment of these phenotypes among the parental output of crosses it appeared that the determinants were located close together on the chromosome.
TL;DR: This analysis revealed that ATCC4117 carries a diploidization gene allelic to or closely linked to HO, modifiers that reduce the number of haploid spores per ascus and alleles affecting the total level of sporulation.
Abstract: ATCC4117 is a strain of S. cerevisiae that undergoes a single nuclear division during sporulation to produce asci containing two diploid ascopores (Grewal and Miller 1972). All clones derived from these spores are sporulation-capable and, like the parental strain, form two-spored asci. In this paper, we describe the genetic analysis of ATCC4117. In tetraploid hybrids of vegetative cells of the ATCC4117 diploid and a/a or alpha/alpha diploids, the production of two-spored asci is recessive. From these tetraploids, we have isolated two recessive alleles, designated spo12-1 and spo13-1, each of which alone results in the production of asci with two diploid or near-diploid spores. These alleles are unlinked and segregate as single nuclear genes. spo12-1 is approximately 22 cM from its centromere; spo13-1 has been localized to within 1 cM of arg4 on chromosome VIII. This analysis also revealed that ATCC4117 carries a diploidization gene allelic to or closely linked to HO, modifiers that reduce the number of haploid spores per ascus and alleles affecting the total level of sporulation.
TL;DR: Results obtained during mapping of the B2t locus strongly suggest a haplo-insufficient site at or closely linked to this locus, which causes disruption of microtubule function in all stages of spermatogenesis, beginning with meiosis.
TL;DR: Chloramphenicol resistance in cells transformed by p1949-2 was mapped to the purA-cysA region of the B. subtilis chromosome, a region and DNA adjacent to the 0.4-kb gene was shown to contain the wild-type allele of genetic marker (tms-26) from that region.
Abstract: A segment of Bacillus subtilis deoxyribonucleic acid (DNA) previously cloned in Escherichia coli contains a gene (the 0.4-kilobase [kb] gene) whose transcription is activated at an early stage of spore development. To map the genetic location of the 0.4-kb gene, we constructed a hybrid plasmid that inserts a chloramphenicol resistance determinant into the B. subtilis chromosome by recombination at a site of homology between cloned B. subtilis DNA and the chromosome. This hybrid plasmid (p1949-2) was constructed from the E. coli plasmid pMB9, the B. sultilis chloramphenicol resistance plasmid pCM194 (whose replication function was inactivated), and B. subtilis DNA from the vicinity of the 0.4-kb gene. Transformation of B. subtilis cells to drug resistance by p1949-2 was dependent upon the B. subtilis RecE+ phenotype and resulted in specific and predictable changes in the pattern of endonuclease restriction sites in the 0.4-kb gene region of the chromosome. Chloramphenicol resistance in cells transformed by p1949-2 was mapped to the purA-cysA region of the B. subtilis chromosome, a region. In addition, DNA adjacent to the 0.4-kb gene was shown to contain the wild-type allele of genetic marker (tms-26) from that region.
TL;DR: These results argue strongly against the involvement of specific excision enzymes, and rather are discussed in terms of a model involving replication of the integrated viral DNA followed by recombination for release of integrated viral sequences.
TL;DR: A Welsh family in which three members have five α-globin genes—three on one chromosome and two on the other and the additional α gene results in an increased α mRNA output and it may therefore produce the phenotype of mild β-thalassaemia.
Abstract: The human genome has two linked α-globin genes on chromosome 16. Deletion of one or more of them, as occurs in α-thalassaemia, leads to a reduced output of α-globin mRNA in proportion to the number of α-globin genes lost1. In some racial groups deletion of one of the pair of α-globin genes may result from unequal crossing over between the genes on homologous chromosomes2,3 by a mechanism resembling that postulated for the formation of the δβ fusion genes of the Lepore haemoglobins4. By analogy, the opposite chromosome in this cross-over should have three α-globin genes just as the ‘anti-Lepore’ chromosome has three non-α-chain genes. We describe here a Welsh family in which three members have five α-globin genes—three on one chromosome and two on the other. The additional α gene results in an increased α mRNA output and it may therefore produce the phenotype of mild β-thalassaemia.
Journal Article•
TL;DR: Of the more than 19 clonal structural chromosome abnormalities observed in these cancers, 6q- and 14q+ were found to be the most frequent and seem to be specifically associated with papillary serous adenocarcinoma of the ovary.
Abstract: Cytogenetic studies were performed in 12 papillary serous adenocarcinomas of the ovary. Of the more than 19 clonal structural chromosome abnormalities observed in these cancers, 6q- and 14q+ were found to be the most frequent. Both markers coexisted in the cells of eight cases; in the other four cases, either a 6q- or 14q+ was present. In at least six cases, the additional segment on the long arm of chromosome 14 appeared to originate, on the basis of the chromosomal quantity and fluorescence pattern, from the missing part of chromosome 6. This suggested that the 6q- and 14q+ markers had arisen as a result of a reciprocal translocation at Bands q21 and q24, respectively, i.e. , t(6;14)(q21;q24). However, it is uncertain in the remaining six cases whether an identical type of translocation was responsible for the formation of the markers. Thus, abnormalities involving chromosomes 6 and 14 seem to be specifically associated with papillary serous adenocarcinoma of the ovary.
TL;DR: In general, DNA transformants grown in the absence of methotrexate were unstable; whereas, under the same conditions about 20% of the transformants from the chromosome experiments were stable.
Abstract: The conditions necessary to achieve high frequency transfer of the thymidine kinase and dihydrofolate reductase genes from hamster cells into mouse cells were investigated. Of the parameters examined, the length of adsorption time, input gene dosage, and treatment with dimethylsulfoxide (DMSO) were found to significantly alter the transfer frequency using either metaphase chromosomes or purified DNA as the transfer vehicle. With the mouse cell line as a recipient, the optimal adsorption period for DNA or chromosomes from MtxRIII cells was found to vary from 8 to 16 h in those experiments where the recipient cells were subsequently treated with DMSO. Without DMSO, similar frequencies could be obtained by extending the period of adsorption. Increasing the dosage of DNA or chromosomes resulted in an almost linear increase in the number of transformants. The optimal conditions for transfer did not significantly differ for the two genes studied. On the average, the optimal conditions yielded 1.5 x 10(3) transformants per 10(7) recipient cells with chromosomes; with DNA an average of only 60 transformants were observed. In general, DNA transformants grown in the absence of methotrexate were unstable; whereas, under the same conditions about 20% of the transformants from the chromosome experiments were stable.
TL;DR: Within‐species karyotype variation is relatively common in aphids, and instances of structural heterozygosity are particularly numerous in species and groups which have partially or completely abandoned the sexual phase of the life cycle in favour of permanent thelytoky.
Abstract: . Diploid female chromosome numbers are listed for 180 aphid species not previously karyotyped. The list includes the first chromosome records for several aphid tribes (Tramini, Greenideini, Anomalaphidini, Nippon-aphidini). Variation in chromosome number at different systematic levels is discussed. Usually the karyotype is particularly stable within a genus, but there are notable exceptions (e.g. Amphorophora) where considerable evolutionary increase in chromosome number has occurred by autosome dissociation with little accompanying morphological change. In several genera differences in gross chromosome morphology can be useful to the taxonomist. Within-species karyotype variation is relatively common in aphids, and instances of structural heterozygosity are particularly numerous in species and groups which have partially or completely abandoned the sexual phase of the life cycle in favour of permanent thelytoky.
TL;DR: The frequency of all types of chromosome abnormalities detected was similar to that found in previous newborn surveys, but the incidence of aneuploid chromosome abnormalities was comparable in the two localities.
Abstract: The results of a chromosome survey of 3993 liveborn infants, the majority of which have been studied using G-banding, are reported. The frequency of all types of chromosome abnormalities detected was similar to that found in previous newborn surveys, which were carried out on different socio-economic structure, but the incidence of aneuploid chromosome abnormalities was comparable in the two localities.
TL;DR: Comparisons showed that chromosomes V and VI originated from arm exchanges between chromosome 2E and other Agropyron chromosomes, and appeared to be related to homoeologous group 2.
Abstract: Genetic compensation of Agropyron chromosomes for wheat chromosomes in the male gametophyte and compensation of Agropyron chromosomes for wheat chromosomes in disomic substitutions were used to investigate relationships between the chromosomes of Agropyron elongatum (Host.) P.B. (2n = 2x = 14) and Triticum aestivum L. emend. Thell. (2n = 6x = 42). Gametophytic compensation indicated that A. elongatum chromosomes I, II, III, IV, and VII were related to wheat chromosomes of homoeologous groups 1, 7, 4, 3, and 6, respectively, and were designated 1E, 7E, 4E, 3E, and 6E. Chromosomes V and VI appeared to be related to homoeologous group 2. Other analyses showed that chromosomes V and VI originated from arm exchanges between chromosome 2E and other Agropyron chromosomes. An unaltered disome of Agropyron chromosome 2E was added to the wheat chromosome complement. In the disomic substitutions Agropyron chromosomes 1E, 6E, and 7E compensated for all three wheat homoeologues of the respective homoeologous groups. C...
TL;DR: The his4-912 mutation shares similar genetic properties with mutations promoted by procaryotic insertion elements, but this mutation lacks all three his4 functions.
TL;DR: It is shown that the loci that control cellular sensitivity to interferon (IfRec) and code for the soluble enzyme superoxide dismutase (SOD-1) are syntenic in the mouse and map to mouse chromosome 16, which will make it possible to use mice trisomic for this chromosome to determine whether certain aspects of the Down syndrome phenotype in man are caused by an altered dosage of IfRec and S OD-1.
Abstract: By using 12 hamster-mouse hybrids segregating a mouse T(16;17)Bnr Robertsonian translocation chromosome in conjunction with 10 similar hybrids segregating normal mouse chromosomes, we have shown that the loci that control cellular sensitivity to interferon (IfRec) and code for the soluble enzyme superoxide dismutase (SOD-1) (superoxide:superoxide oxidoreductase; EC 1.15.1.1) are syntenic in the mouse and map to mouse chromosome 16. IfRec and SOD-1 are also syntenic in man. They have previously been assigned to the distal segment of the long arm of human chromosome 21, trisomy for which causes Down syndrome. Because both IfRec and SOD-1 map to mouse chromosome 16, it will now be possible to use mice trisomic for this chromosome to determine whether certain aspects of the Down syndrome phenotype in man are caused by an altered dosage of IfRec and SOD-1.
TL;DR: Detailed analysis of the missing chromosomes revealed the loss of a No. 22 chromosome, an aberration specific for meningioma, which is discussed in the light of findings, obtained to-date, in the field of tumor cytogenetics.
TL;DR: Results indicate that structural genes for the gamma 2b-, mu-, and alpha-heavy chain-constant regions map to the distal half of this chromosome.
Abstract: To determine the chromosomal location of mouse immunoglobulin heavy chain structural genes unambiguously, a panel of somatic cell hybrids was scored for the presence of DNA sequences homologous to gamma 2b-, mu-, and alpha-heavy chain-constant region DNA probe molecules. The hybrids, formed between mouse and hamster cells, contained various combinations of mouse chromosomes plus a full set of hamster chromosomes. Hybrids that retained mouse chromosome 12 reacted with the probes, whereas hybrids that had lost the chromosome, or its distal half, failed to react. These results indicate that structural genes for the gamma 2b-, mu-, and alpha-heavy chain-constant regions map to the distal half of this chromosome.
TL;DR: It was found that four disomic chromosome addition lines could be distinguished from one another and from the other three possible lines on the basis of the zymogram phenotypes of these isozymes.
Abstract: The alcohol dehydrogenase (ADH), glutamic oxaloacetic transaminase (GOT), aminopeptidase (AMP), endopeptidase (EP), and esterase (EST) zymogram phenotypes of Chinese Spring wheat, Betzes barley, Chinese Spring-Betzes heptaploids, and a number of presumptive Betzes chromosome additions to Chinese Spring were determined. It was found that four disomic chromosome addition lines could be distinguished from one another and from the other three possible lines on the basis of the zymogram phenotypes of these isozymes.The structural gene Adh-H1 was located in Betzes chromosome 4, the genes Got-H2 and Amp-H1 in chromosome 6, and the gene Ep-H1 in chromosome 1. These gene locations provide evidence of homoeology between Betzes chromosomes 4, 6, and 1 and the Chinese Spring chromosomes of homoeologous groups 4, 6, and 7, respectively.
TL;DR: Interestingly, human chromosome 14, which carries the genes for human immunoglobulin heavy chains, appears to be retained by almost all the hybrid clones and subclones.
Abstract: Loss of human chromosomes from mouse × human hybridomas is not random. Human chromosomes 14, 5 and 22 are preferentially retained, while chromosomes 2 and 1 are preferentially lost. Interestingly, human chromosome 14, which carries the genes for human immunoglobulin heavy chains, appears to be retained by almost all the hybrid clones and subclones.
TL;DR: For most hamster chromosomes, there is a strong correlation between relative fluorescence and stain base preference suggesting that staining differences may be determined primarily by differences in average base composition.
Abstract: The cytochemical properties of metaphase chromosomes from Chinese hamster and human cells were studied by flow cytometry. This technique allows precise quantitation of the fluorescence properties of individual stained chromosome types. Chromosomes were stained with the following fluorescent DNA stains: Hoechst 33258, DAPI, chromomycin A3, ethidium bromide, and propidium iodide. The relative fluorescence of individual chromosome types varied depending on the stain used, demonstrating that individual chromosome types differ in chemical properties. Flow measurements were performed as a function of stain and chromosome concentration to characterize the number and distribution of stain binding sites. Flow analysis of double stained chromosomes show that bound stains interact by energy transfer with little or no binding competition. For most hamster chromosomes, there is a strong correlation between relative fluorescence and stain base preference suggesting that staining differences may be determined primarily by differences in average base composition. A few hamster chromosome types exhibit anomalous staining which suggests that some other property, such as repetitive DNA sequences, also may be an important determinant of chromosomal staining.
TL;DR: Southern blot hybridization studies using cloned μ, γ1 and γ2b-chain genes as probes demonstrate that the μ- andγ1-chain gene of the expressed chromosome are deleted while these genes of the unexpressed chromosome are retained.
Abstract: We have studied the organization of immunoglobulin heavy-chain genes in a γ2b-chain (BALB/c allotype)-producing myeloma BKC F1 #15 induced in a F1 mouse between C57BL and BALB/c. Southern blot hybridization studies using cloned μ, γ1 and γ2b-chain genes as probes demonstrate that the μ- and γ1-chain genes of the expressed chromosome are deleted while these genes of the unexpressed chromosome are retained. The γ2b-chain gene of the expressed allele is rearranged while that gene of the unexpressed allele seems unchanged, as do the γ2a-chain genes. These results support the allelic deletion mechanism in heavy-chain class switch and the order of H chain genes.