Replication pattern of the X and Y chromosomes in partially synchronized human lymphocyte cultures

The replication pattern of the X and Y chromosomes at the beginning of the synthetic phase was studied in human lymphocyte cultures partially synchronized by the addition of 5-fluoro-2-deoxyuridine (FUdR). The data were evaluated statistically by an analysis of the distribution of silver grain counts over the X and Y chromosomes. —In cells from normal females, one of the X chromosomes began replication later than any other chromosomes of the complement. The short arm of the late replicating X chromosome started replication earlier than the long arm. The telomeric region of the short arm was a preferential site of DNA synthesis at the beginning of replication. —In partially synchronized lymphocyte cultures from a patient with the XXY syndrome, the Y chromosome started replication together with the late replicating X chromosome. The Y chromosome most frequently replicated synchronously with the short arm of the X. The centromeric region of the Y chromosome initiated synthesis before the telomeric region and appeared to replicate synchronously with the telomeric region of the short arm of the X. These findings are discussed with reference to the pairing of the X and Y chromosomes at meiosis.Supported in part by the National Institute of Health Research Grant HD-01979 and National Foundation Birth Defects Research Grant CRCS-40. Dr. Knight was a predoctoral fellow under National Institute of Health Training Program HD-00049-09.     

Underreplication of a polytene chromosome arm in the chironomid Prodiamesa olivacea

The genome of Prodiamesa olivacea (Diptera, Chironomidae) has a 2 C DNA content of 0.25 pg. Mitotic metaphases reveal 3 pairs of chromosomes: 2 metacentric ones and one submetacentric. The latter comprises 20.8% of total Feulgen DNA. During larval polytenization the complemental portion of the 3rd falls to 6.5%. Concomitantly the polytene 3rd chromosome is much shorter than expected. It has no constriction and is shaped like a ball sector. — Underreplication is understood as suppression of DNA syntheses mainly in the long arm of the 3rd chromosome at the first to third endoreplicative cycle. Most of the dense heterochromatin seen in the apex of the 3rd polytene element is not itself underreplicated; it conceals the underreplicated long arm of this chromosome. — In ovarian nurse cells which are closely connected with the germ line the longer heterochromatic arm of the 3rd polyneme chromosome is fully replicated. — Underreplication is discussed in the context of DNA silencing.     

一例t（Y;15）并t（14;21）复合易位的细胞与分子遗传学研究

本文对一便生育过先天愚型儿的个体刊进行了细胞与分子遗传学研究。发现先证者拥有ｔ（１４;２１）用一个短臂增大变异为１５号标记染色体。通过Ｇ－显带、Ｃ－显带、Ｑ－显带、硝酸银染色及Ｙ染色体长臂异染色质区特异控针ｐＹ３．４对先证者基因组ＤＮＡ的斑点杂交和中期染色体的原位杂交,证实变异部分由Ｙ染色体长臂异染色质区易位所形成,从而排除了巨大随体的存在或其他染色体参与重排形成变的可能性,结果表明,常规显带与染     

Induced chromosome aberrations in early embryogenesis of mice

Summary A 28-year-old man, whose infant son died of multiple malformations, was shown to have a balanced 13q-/18q+ translocation. He was phenotypically and mentally normal. Studies of the pedigree revealed the presence of bilateral microtia on the side of the spouse of the proband, transmitted in a dominant mode through four generations. Occasional cells from the proband and his mother exhibited an elongated long arm of a chromosome 16.This work was supported by a grant from the National Swiss Foundation for Scientific Research (Credit No. 3.211.69).Supported by Grant 64-411A from the Ford Foundation Population Program.     

Fragile site long arm chromosome 16

Summary A fragile site at the long arms (q21) of chromosome 16 was found in two persons, each of whom became the parent of a child with a de novo structural chromosome abnormality—a balanced autosomal translocation and an autosomal deletion. The question of an increased risk of structural chromosome abnormalities in the offspring of persons with fragile site long arm 16 is discussed.     

Polymorphic patterns of heterochromatin distribution in guinea pig chromosomes

The chromosome complement and patterns of heterochromatin distribution (as demonstrated by the DNA d-r method) were studied from three different guinea pigs. Karyotype analyses showed that one of the females had a heteromorphic sex pair formed by a submetacentric X chromosome and a subterminal X chromosome originated by a shortening of the short arm (x-chromosome). The heterochromatin was mainly found in the pericentromeric areas of the autosomes and X chromosomes and in the short arm of pair 7. The Y chromosome exhibited a degree of heterochromatinization different from that of pericentromeric areas.—The analysis of the heterochromatin distribution in the X chromosomes showed that the smaller size of the heteromorphic x-chromosoine was probably due to a lack of heterochromatin in its short arm. Moreover, two out of the three animals studied had a heteromorphic pattern of heterochromatinization in the pair 21 characterized by heterochromatinization of the pericentromeric area in one chromosome and almost complete heterochromatinization of the other homologue.—It is suggested that most of the heterochromatin disclosed by the DNA d-r method is formed by repetitious DNA; and that the Y chromosome and perhaps some autosome regions in guinea pigs are formed by a type of heterochromatin with properties different from those of the constitutive and facultative heterochromatin (intermediate heterochromatin).Supported in part by NIH Grant 5-501-RR05672-02 and by NIH contract 70-2299.     

Chromosome size and DNA content of species of anemone L. and related genera (Ranunculaceae)

Relative amounts of DNA were determined by Feulgen cytophotometry in 22 diploid species of Ranunculaceae (n=7, 8, 9) representing six genera, and exhibiting large differences in chromosome size, but no marked differences in karyotype pattern. Chemical determination of absolute amounts of DNA for six of these species, allowed conversion of all the photometric data into absolute units of DNA. The mean DNA content per nucleus varied from.13×10^–11gm in Aquilegia to 5.25×10^–11gm in species of Anemone in the section Homalocarpus. The DNA values obtained appeared to be quantized, and data for the majority of species fitted a non-geometrical series with the observed relative terms: 1—8—12—16—20—24—40. The magnitude of these variations in DNA content, the preservation of the karyotype and the tendency towards a simple numerical progression in DNA values, lead us to prefer an interpretation of the evolution of DNA content in terms of differential polynemy to one postulating changes in size of genetic units in an unchanging number of strands per chromosome.     

Chromosome mapping in barley by means of telotrisomic analysis

Summary A total of 37 genetic markers located in chromosomes 2, 3, 4 and 5 were associated with specific arms by means of telotrisomic analysis in five telotrisomics (Triplo 2 L, 2 S, 3 S, 4 S, 5 L) of barley (Hordeum vulgare L.). The genes v, gp (= gp 2), li, gs 5, tr and msg2 showed a trisomic ratio with Triplo 2 L indicating that these genes were on the long arm of chromosome 2. A disomic ratio was obtained for genes wst 4, gs 5, and v with Triplo 2 S, confirming that these genes were on the long arm of chromosome 2(2 L). A disomic ratio was observed for genes e, f(= lg), sk, and gs6 with Triplo 2 L. Two genes, f(= lg) and gs6 showed a trisomic ratio with Triplo 2S. These results indicated that genes e, f(= lg), sk, and gs 6 are on the short arm of chromosome 2 (2S). Since only one telocentric chromosome was available for chromosome 3, 4 and 5, most of the well-mapped marker genes were tested with those telocentric chromosomes. The genes cu 2, uz, wst, als, gs 2, zb,f2, and cer-zn ³⁴⁸ showed trisomic ratio with the telocentric for chromosome 3. These genes were located on the short arm of chromosome 3 (Robertson 1971). This indicated that the telocentric chromosome is for the short arm of chromosome 3(3 S). A disomic ratio was obtained for genes yst, x _c, al, yst2, a _n, ari-a ⁶ and x _s, indicating that these genes are on the long arm of chromosome 3. Two genes, f9 and K, showed trisomic ratio with the telocentric chromosome for 4, while genes gl(= gl2), br2, yh, lg 3, lg 4 and lk 5 showed disomic ratios. This indicated that the telocentric chromosome is for the short arm of chromosome 4. Two genes, fs 2 and g, were studied with Triplo 5 L. Both showed trisomic ratio, indicating that fs 2 and g are located on Triplo 5 L. The centromere position (C) on chromosome 2, 3 and 4 was thus located as (the left side of C is the short arm and the right is the long arm): chromosome 2: f — sk — gs6 — e — C — gs5 — msg2 — wst4 — v — gp — li — tr; chromosome 3: f2 — cer-zn ³⁴⁸ — uz — gs2 — als — cu2 — wst — zb — C — yst — x _c — al — yst2 — a _n — ari-a ⁶ — x _s; chromosome 4: f9 — K — C — lg4 — lg ³ — gl2 — br2 — lk5 — yh. The centromere position on chromosome 5 was not precisely located.Contribution from the Department of Agronomy, Published with the approval of the director of the Colorado State University Experiment Station as Scientific Series Paper No. 2606. This research was supported in part by by NSF Grant GB 4482X and GB 30 493 to T. Tsuchiya and Colorado State University Experiment Station Hatch Project     

Characterization of three de novo derivative chromosomes 16 by “Reverse chromosome painting” and molecular analysis

We have analyzed three de novo chromosome 16 rearrangements—two with a 16p+ chromosome and one a 16q+—none of which could be fully characterized by conventional cytogenetics. In each case, flow karyotypes have been produced, and the aberrant chromosome has been isolated by flow sorting. The origin of the additional material has been ascertained by amplifying and labeling the DNA of the abnormal chromosome by degenerate-oligonucleotide-primer–PCR and hybridizing it in situ to normal metaphase spreads (reverse chromosome painting). Both 16p+ chromosomes contain more than 30 Mb of DNA from the short arm of chromosome 9 (9p21.2-pter), while the 16q+ contains approximately 9 Mb of DNA from 2q37. The breakpoints on chromosome 16 have been localized in each case; the two breakpoints on the short arm are at different points within the terminal band, 16p13.3. The breakpoint on the long arm of chromosome 16 is very close to (within 230 kb of) the 16q telomere. Determination of the regions of monosomy and trisomy allowed the observed phenotypes to be compared with other reported cases involving aneuploidy for these regions.     

A 46, XY,del(18)(pter→pl 100:) Cebocephalic child from a 46, XX,t(12;18)(18pter→18pl 100 :: 12qter→12pter) normal parent

Summary A normal female with an 18p—chromosome but without any feature of the 18p—syndrome produced a cebocephalic child whose karyotype included an 18p—chromosome. Evidence is presented that the normal female is a nonreciprocal translocation heterozygote resulting from the short arm of one chromosome 18 becoming attached to the long arm of a chromosome 12.     

Comparative study of human chromosome replication in primary cultures of embryonic fibroblasts and in cultures of peripheral blood leucocytes

Distributions of AT- and GC-base pairs along the length of chromosomes 1, 2, 3 and 16 in primary cultures of embryonic fibroblasts and of peripheral blood leucocytes were studied by autoradiography with: 1. ³H-thymidine and ³H-deoxycytidine; 2. ³H-deoxyadenosine and ³H-deoxyguanosine. It has been shown that the two types of cells differ in the DNA content and proportion of AT- and GC-nucleotide pairs in the centromeric heterochromatin of chromosome I: this region contains more DNA in fibroblasts than in leucocytes mainly due to AT-pairs. In both types of cells the telomeric region of the short arm of this chromosome contains more GC- than AT-pairs. Similar results were obtained for C-heterochromatin of chromosome 16: the frequencies of labelling of this region by ³H-deoxyadenosine and ³H-thymidine in fibroblast cultures were higher than in case of ³H-deoxycytidine and ³H-deoxygyanosine, and in leucocyte cultures these frequencies were almost equal. No differences in the distributions of base pairs along the length of chromosome 2 and 3 were established in the two types of cells. — The nature of the established phenomenon may be connected with under-replication or loss in another way of part of the genetic material in the process of development and differentiation of cell systems.     

Human inherited marker chromosome 22 short-arm enlargement: Investigation of rDNA gene multiplicity,Ag-band size,and acrocentric association

Summary The banding characteristics of an extreme variant familial chromosome 22 short-arm enlargement are described. Ag-AS staining for nucleolar-organizer regions, identified two areas of rDNA actively coding for 18S and 28S rRNA, the one being a broad distal Ag-band and the other a narrower centromeric Ag-band. The DNA in the major portion of the enlarged short arm was highly methylated, as shown by the binding of antibodies to 5-methylcytidine after UV-denaturation of chromosomal DNA. Mean Ag-band size on the aberrant 22p⁺ correlated with the mean number of 22p⁺ associations. Association of 22p⁺ was no greater than that of other acrocentrics, in spite of a presumed excess number of rDNA gene copies. This case represents only the second such normal variant defined by these techniques.     

Mapping of human thyroglobulin gene on the long arm of chromosome 8 by in situ hybridization

Summary We report the structural organization of a segment of the human thyroglobulin gene, located 70kb from the 3 end of the gene, containing the exons 8 and 9 starting from the 3 end. Selected probes from this region have been used for the chromosomal mapping of the thyroglobulin gene by in situ hybridization techniques. Only one site in the human haploid karyotype is labeled with the genomic DNA probes. Twenty percent of the grains are localized on the long arm of chromosome 8, mostly in the subregion q-2-23 q-2-24 of the long arm of chromosome 8. The localization of the autoradiographic grains suggests a subregional assignment of the human thyroglobulin gene locus to 8q 2–23 or 8q 2–24.     

The behavior of isochromosomes and telocentrics in wheat

Summary Genetic tests with chromosome IX of common wheat showed 13.3% formation of isochromosomes from telocentrics as against 7.0% for the same long arm of normal IX, and 7.0% formation of telocentrics from each arm of iso-IX instead of 10.8% from the same arm of normal IX. The differences are not significant statistically.No differences in frequency of formation of isochromosomes were found among 16 independently produced telocentrics for the long arm of chromosome IX.Somatic loss of both telocentrics and isochromosomes for chromosome IX and other wheat chromosomes has been observed, with loss of the telo being somewhat more frequent. A telocentric gave rise, to an isochromosome somatically. and isochromosomes added a telocentric. Two complex aberrations involving loss and duplication of parts of arms were observed, one of a telo and one of an iso; but these aberrations probably occurred at meiosis.Senior Geneticist, Division of Cereal Crops and Diseases, Bureau of Plant Industry, Soils, and Agricultural Engineering, Agricultural Research Administration, U. S. Department of Agriculture; and Research Associate, Field Crops Department, University of Missouri. This work was supported in part by funds obtained under Bankhead-Jones Project SRF 2–95, Combining in Wheat the Disease Resistance and Other Desirable Characters of Related Grass Species. Journal Paper No. 1269 of the Missouri Agricultural Experiment Station.     

Location of messenger specifying sequences in mammalian chromosomes

In situ hybridization of complementary DNA (cDNA) synthesized from total cytoplasmic polyadenylated RNA isolated from Chinese hamster cells was employed to investigate the distribution of messenger specifying sequences on mammalian chromosomes. The kinetics of cDNA-nuclear DNA annealing indicate that about 85% of the cDNA represents sequences which are transcribed from non-repetitive DNA sequences. When cDNA is hybridized back to its template RNA, the reaction kinetics show that more than 60% of the poly(A) RNA is at least 10⁴ times more complex than rabbit globin mRNA. In situ hybridization of cDNA to Chinese hamster cells fixed on slides shows no significant clustering of silver grains on interphase nuclei. On metaphase chromosomes the majority of silver grains are localized in euchromatic areas. It appears that all euchromatic segments have similar grain densities. Chromosomes 1 and 2, which have relatively little heterochromatin, do not have a higher grain density than the other chromosomes. However, the Y chromosome, which is entirely heterochromatic, contains only about 1/3 the grain density of the chromosomes 1 or 2. — When the cDNA, which anneals only to the high abundancy class of poly(A) RNA was fractionated and hybridized in situ to Chinese hamster chromosomes, the distribution of silver grains is localized in the euchromatic areas. The Y chromosome and the heterochromatic arm of the X chromosome contain less grains; telomeres of some autosomes have higher grain densities. The oligo-(dT) primer in cDNA did not affect the results of this study since no grains are found when ₃H-poly(dT) was used as probe for in situ hybridization. The majority (>90%) of the grains could be blocked by competition with excess repetitive DNA in the hybridization reaction, indicating that the in situ hybridization involved predominantly repetitive sequences.     

Variability of C-banding patterns in Japanese quail chromosomes.

Observations were made of the C-banding patterns in several cells from 182 Japanese quail embryos to detect presence of stable variants. Each of the eight largest autosomes contains a C-band at the centromeric region. The short arm of autosome 8 is C-band positive, as is the entire W chromosome. The Z chromosome consistently contains an interstitial C-band in the long arm and a less prominent one in the short arm. Distinct variants of chromosome 4 and the Z chromosome were observed. In the Z chromosome a C-band at the terminal region of the short arm was markedly elongated in some embryos. Likewise, the short arm of chromosome 4 was much more prominent in one or both of the homologues in some embryos. Most of the microchromosomes contain a prominent C-band. The heteromorphisms are useful chromosome markers to detect the origins of heteroploidy in early embryos.     

Chromosomal banding patterns in human large bowel adenomas

Summary The human thyroglobulin gene was mapped by in situ hybridization whereby a ³H-labeled recombinant plasmid DNA containing a fragment of 2.3 kilobases of human thyroglobulin gene was hybridized to human chromosome preparations. A high proportion (25%) of hybridized metaphases exhibited silver grains at the distal portion of the long arm of chromosome 8. Analysis of the grain position at this site indicated that the chromosomal localization of the human thyroglobulin gene was 8q242-8q243.     

Karyological studies on fifteen forms of amphisbaenians (Amphisbaenia-Reptilia)

The chromosome constitutions of 15 forms (2 acrodonts and 13 pleurodonts) of amphisbaenians belonging to two families and eight genera were studied. The diploid chromosome numbers varied from 30 to 44 with the number of chromosome arms (FN) ranging from 42 to 60. The karyotypes of 12 forms all contained 6 pairs of macrochromosomes with similar morphology and 9 to 12 pairs of microchromosomes. The remaining three species had a higher diploid number (40–44) and a wide variation in chromosome morphology. Karyotype variations were found in the same family, even in the same genus. The lengths of the 6 pairs of macrochromosomes in 5 of the 12 forms were measured and compared. This disclosed similarities in the mean lengths, relative lengths, and arm ratios of those forms. — Chromosome patterns found in the present study support, in general, the classification of amphisbaenians derived from analysis of morphological characters.Supported in part by United Health Foundation of Western N. Y. Research Grant G-66-RP-9, National Cancer Institute, CA-08737 and NSF GB 2460.     

Localization of viral transforming sequences within marker chromosomes associated with tumor formation and progression in a murine fibrosarcoma

The low-metastatic RSV-transformed fibrosarcoma line B77-3T3 and its metastatic variant AA12, selected in vitro, have been analysed by blot and in situ hybridization with v-src and murine c-myc specific probes in order to detect molecular rearrangements underlying the transition from the low-metastatic to the high-metastatic phenotype. Previous cytogenetic analysis had evidenced that a marker chromosome of the parental tumor line (chromosome A) is replaced in the metastatic counterpart by a new marker chromosome (chromosome B), possibly arisen by duplication of a chromosome A segment, included between two C-positive regions (L. Doneda et al., 1985). In situ hybridization on chromosome spreads of the two related lines with a ³H-labelled v-src probe showed that src sequences are located within the marker chromosomes A and B, and the percentage of grains over the AA12 marker chromosome is always double that found on the B77-3T3 marker. These signals were considered to identify v-src sequences as they were found to be slightly amplified in the metastatic variant DNA by blot hybridization with the v-src probe. As regards the intrachromosomal location of the signals, most grains were clustered near the heterochromatic bands, suggesting a possible role for heterochromatic sites in tumor formation and evolution. No involvement of the A and B marker chromosomes was shown by in situ hybridization experiments with a c-myc probe. However the dosage of c-myc sequences was also found to be slightly increased in the metastatic variant DNA.     

Querscheibenspezifische Unterschiede in der3H-Thymidin-Markierung während der Larvenentwicklung vonChironomus thummi piger

In salivary gland chromosome II ofChironomus, region A2j-A3(d) replicates during the whole replication cycle.³H-thymidine is incorporated in this region for a longer time than in bands of greater DNA values (Hägele, 1970). However, no extra DNA is accumulated in A2j-A3(d). Therefore it was supposed that in addition to the duplication of structural DNA an extra DNA is synthesized which immediately disappears from the chromosome. In this report the attempt was made to test this hypothesis. — Using³H-thymidine, the autoradiographic patterns have been studied which occur in the salivary gland chromosomes II ofChironomus thummi piger at the end of a replication step. The probable order of their sequence has been established. At the mid phase of a replication step region A2j-A3(d) and a certain number of definite bands are labelled whereas at the very end of DNA synthesis only A2j-A3(d) shows labelling. It is demonstrated that this region replicates for a longer time than regions containing up to 3.8 times more DNA. Moreover in most cells³H-thymidine is incorporated in region A2j-A3(d) at the end of synthesis at a higher rate than in late replicating bands. In this region there exists a considerable difference in relative grain density within the same phase of a replication step. This difference cannot be found in other bands studied. — These labelling patterns occur in chromosomes of both young larvae (8–9 days old) and prepupae (15–17 days old) if the larvae are prepared immediately after incubation in the isotope. — However, if young larvae are incubated in³H-thymidine and then develop to prepupae in water free of isotope region, A2j-A3(d) is unlabelled at the end of a replication step in half of the cells studied. In the other half this region shows labelling but the relative grain density is markedly reduced. The labelling pattern of other bands is not changed. Therefore loss of radioactive DNA in A2j-A3(d) is of real occurrence. — This loss probably takes place within the replication steps 1 or 2 between young larvae and praepupae. In these replications the structural DNA and the extra DNA, newly synthesized in A2j-A3(d), are unlabelled. The extra DNA disappears immediately from the chromosome. If, by chance, an exchange takes place between newly synthesized unlabelled DNA chains of extra DNA and old labelled DNA, then loss of radioactive DNA would be the result.