Phenotypic effects of balanced X-autosome translocations in females: a retrospective survey of 104 cases reported from UK laboratories

Females with balanced X-autosome translocations are a clinically heterogeneous group of patients in which X breakpoint position and replication behaviour may influence phenotypic outcome. This study reviewed all cases reported by UK cytogenetics laboratories over a 15-year period (1983-1997). Publication bias was avoided by reviewing all reported cases. One hundred and four female carriers were identified, 62 of who were probands. By reason for referral, these were: multiple congenital abnormalities and/or developmental delay (MCA/DD): 26 (42%); gonadal dysfunction: 22 (35%); phenotypically normal with or without recurrent miscarriage (NRM): 9 (15%); recognized X-linked syndrome: 5 (8%). The information obtained was compared with published data and with data from the authors' own laboratories of female patients with balanced autosome-autosome translocations (n=115). We concluded that: (1) MCA/DD cases were significantly over-represented compared to previous published data (P<0.005) and were more common than in female probands with balanced autosome-autosome translocations (P<0.05). (2) MCA/DD cases showed random breakpoint distribution along the X chromosome (P>0.05). MCA/DD cases with subtelomeric breakpoints at Xp22 or Xq28 were not always associated with deviation from the expected pattern of X-inactivation where this was known. De novo cases were significantly more likely to be assigned as MCA/DD than any other category (P<0.005). (3) Gonadal dysfunction (GD) was invariably associated with a 'critical region' breakpoint, Xq13-q26, (20/22 probands). However, 7/44 (16%) of patients surveyed had breakpoints within Xq13-Xq26 and proven fertility. (4) Recognized 'X-linked syndrome' cases were significantly under-represented (P<0.001) compared to previous published data.     

Translocation Down syndrome in Ohio 1970-1981: epidemiologic and cytogenetic factors and mutation rate estimates.

Sixteen hundred eighty-eight Down syndrome live births, including 65 (5.2%) translocations, were ascertained in Ohio between 1970 and 1981. Translocations of known origin were 24.4% maternal, 2.2% paternal, and 73.3% de novo. Translocation subtypes were 14/21 (45.7%), 15/21 (2.9%), 21/21 (40.0%), 21/22 (2.9%), and other (8.5%). Among 14/21 translocations, 33.3% were maternal in origin and 66.7% were de novo, while 100% of 21/21 translocations were de novo. No differences were found when the maternal- and paternal-age distributions of all translocations or various translocation subsets were compared with the live-birth control distributions. However, mean maternal and paternal ages of de novo translocations were significantly lower than that of the live-birth controls. Ohio data showed the average maternal age of de novo D/21 cases to be significantly lower than the control. Ages of both parents of de novo G/21 cases and paternal age of D/21 cases were not different from the control. De novo translocation mutation rate estimates were 0.8 X 10(-5) for 14/21, 1.2 X 10(-5) for 21/21, and 2.2 X 10(-5) overall. Ohio estimates (3.2 X 10(-5) for 1970-1972 and 1.4 X 10(-5) for 1973-1975) did not reflect the increase in mutation rate previously found in New York during 1973-1977.     

Cytologic observations in 35 individuals with a 5p- karyotype

Summary Chromosome investigation of 35 individuals with a 5p- karyotype and their families revealed the presence of 27 apparently terminal deletions, four interstitial deletions, and four translocations, including two familial cases. Four of the probands with simple deletions and one of the mothers were mosaics. Unusual chromosomal heteromorphism, as rendered visible after acridine orange staining, was observed on the short arm of chromosome 14 in two cases and, after heterochromatin staining, on chromosome 19 in one family. Measurement studies, carried out in probands with simple deletions and in two control groups, showed a short-arm loss clustering between 32% and 62% of the normal short-arm length. Using at least two complementary staining methods per proband, we found that the midportion of the 5p15 segment probably must be deleted to develop the typical clinical features of the cri du chat syndrome.     

The 11q;22q translocation: A European collaborative analysis of 43 cases

Summary Translocation between the long arms of chromosomes 11 and 22 is usually detected in offspring with an unbalanced karyotype following a 3:1 disjunction resulting in partial trisomy. Since by the end of 1976 it was suspected that this translocation might be more frequent than one would deduce from published reports, it was decided to call for a collaborative effort in Europe to collect unpublished cases. In response, 42 cases were collected in Europe, and one case from New Zealand was added. The following countries were represented with the number of cases indicated in parentheses: Czechoslovakia (2), Denmark (4), Finland (3), France (6), Germany (1), Italy (5), The Netherlands (9), Sweden (6), United Kingdom (4), Yugoslavia (2). The wide geographical distribution indicates a multifocal origin of the translocation. Among the unpublished cases, 31 were ascertained as unbalanced carriers [47,XX or XY,+der(22),t(11;22)] and 12 as balanced balanced carriers [46,XX and XY,t(11;22)]. Among the published cases, 10 were ascertained in unbalanced and 3 in balanced carriers. The breakpoints of the translocations indicated by the contributors varied, the most frequently reported being 11q23;22q11 (25 cases), followed by q25;q13 (10 cases). While the first one seems more likely, it was not possible to decide whether the breakpoints were the same in all cases.All 32 probands with unbalanced karyotypes had inherited the translocation, 31 from the mother and only 1 from the father. This ratio became 43:1 when the published cases were added. A segregation analysis revealed that in families ascertained through probands with unbalanced karyotypes there was a ratio of carriers to normal (all karyotyped) 54:55, not a significant difference. The formal maximum (minimum) recurrence risk for this unbalanced translocation was calculated to be 5.6% (2.7%). When the ascertainment was through a balanced proband, the maximum risk was 2.7%. The risk was calculated as 5.7% for female and 4.3% for male carriers. The mean family size was 1.67 for the offspring of female carriers and 0.78 for the offspring of male carriers. This significant difference suggests that heterozygosity for the translocation reduces fertility in males. Indeed, several of the probands with balanced karyotypes were ascertained because of sub- or infertility. Only 2 de novo translocations were found among the 59 probands, and both, were among the 12 cases ascertained as balanced carriers. The source, quality, and quantity of the clinical data for the subjects with unbalanced karyotypes were variable, and no definite conclusions were possible about phenotypes. The following signs were recorded in 10 or more of the 45 cases: low birth weight, delayed psychomotor development, hypotonia, microcephaly, craniofacial asymmetry, malformed ears with pits and tags, cleft palate, micro-/retrognathia, large beaked nose, strabismus, congenital heart disease, cryptorchidism, and congenital dislocation of the hip joints. Many signs were similar to those considered typical of trisomy 11q, and the phenotype coincided almost completely with the presumptive phenotype of complete trisomy 22. No cases with coloboma was recorded, while other signs of the cat-eye syndrome were found in several probands. This might indicate that individuals with the cat-eye syndrome and carriers of the unbalanced 11/22 translocation have the same segment of 22 in triplicate plus or minus another chromosome segment.     

Unbalanced Robertsonian translocations associated with Down's syndrome or Patau's syndrome: Chromosome subtype,proportion inherited,mutation rates,and sex ratio

Summary Summary data are presented on 168 D/21 and 131 G/21 translocation trisomies reported to the New York State Chromosome Registry. By combining these data with others from the literature it is estimated that about 59% of D/21 cases are the result of mutation in the parental generation; the rest are translocations inherited from parental carriers (39% maternal, 3% paternal). The proportion of mutants is about 10% greater for 14/21 cases and significant lower for 13/21 cases. Of G/21 cases 93% are mutant, about 6% of maternal origin, and 1% of paternal origin. All the mutant cases involve 21/21 rearrangements. Estimated mutation rates per 10⁵ gametes for translocation trisomies in affected livebirths are 0.1 for 21/13, 0.5 to 0.9 for 21/14, and 1.1 to 1.4 for 21/21. The rates for 21/15 and 21/22 translocation trisomies are probably all conservatively less than 0.1 per 10⁵ gametes. Of interchange trisomy Patau's syndrome, about 60% of cases are mutant; the rest are translocations inherited from a parental carrier (about 25% for 13/13 cases and about 45% for 13/14 cases. The estimated mutation rates for 13/13 and 13/14 interchange trisomies are each about 0.5 per 10⁵ gametes; the rate for 13/15 interchange trisomies is less than 0.1 per 10⁵ gametes. A male excess is observed for D/21 (sex ratio=1.70), and G/21 (sex ratio=1.38) interchange Down's syndrome, and a female excess for D/13 interchange Patau's syndrome (sex ratio =0.77), trends similar to those seen in the respective 47, trisomies associated with these phenotypes.     

Analysis of translocations observed in three different populations. I. Reciprocal translocations

A sample of 437 reciprocal translocations was classified into three groups according to their method of ascertainment (Group I = couples with repeated abortions; Group II = karyotypically unbalanced carriers; Group III = balanced translocation heterozygotes). Statistical analysis showed that the distributions of chromosome breaks observed in the three groups could not be accounted for by chromosome arm length alone. In couples with repeated abortions, an excess of breaks in 7p, 17p, and 22q was found, whereas in the balanced translocation heterozygotes an excess of breaks was found only in 11q. An excess of breaks was found in arms 9p, 14p, 18p, 18q, 21q, and 22q in karyotypically unbalanced probands. A significant decrease of breaks in the medial chromosome regions was accompanied by a concomitant increase in the terminal regions in all groups. The three groups demonstrated different distributions of chromosome arm involvement in the observed translocations. Balanced translocation heterozygotes had the highest frequency of large (greater than the length of 4p) translocated segments and an excess in the frequency of large-large translocations, whereas karyotypically unbalanced probands had the highest frequency of small (shorter than 21q) translocations and an excess in the frequency of small-small translocations. For each type of chromosomal imbalance observed, the balanced translocation heterozygotes demonstrated the greatest potential imbalance and the karyotypically unbalanced probands the least.     

Variant Philadelphia translocations in chronic myeloid leukemia

Up to the beginning of 1986, some 327 variant Philadelphia translocations were reported in chronic myeloid leukemia. The present study represents an attempt to determine which factors (sex, age, geographic localization, etc.) influence the occurrence and chromosome involvement of these variant Philadelphia (Ph1) translocations. Clinical data indicated that band 9q34 was always rearranged in the variant Ph1 translocations and no difference existed between the hematologic and prognostic features among patients with the standard and the variant translocations. An uneven geographic distribution of the variant Ph1 translocations was found. Whether this was due to populations with different ethnic backgrounds or to environmental factors could not be determined. Twenty-eight bands were shown to be rearranged more frequently than expected (P less than 0.05); 27 of them are known to contain a fragile site and/or an oncogene and/or are rearranged more frequently than expected in other malignancies. The chromosomes involved in these variant Ph1 translocations were found to show a very particular geographic distribution, which cannot be explained at present.     

Results of estimation of mutation rates for translocation trisomy 21

Among 1332 cases of trisomy 21 born within 1979-1999 in St. Petersburg, 76(5.7%) were carriers of a translocation between chromosome 21 and other acrocentrics. Among 43 Dq; 21q translocations, 17 were inherited from the mother, and one was inherited from the father, 16 were of sporadic occurrence, and in 9 cases the mode of inheritance was not established. Out of 31 cases displaying Gq;21 translocation, 23 were mutants and 8 of unknown origin. One case of non-Robertsonian translocation 21;22 was maternal in origin. It was assumed that the proportion of sporadic cases among translocations of unknown origin is the same as that among translocations of the known origin. However, it is conceivable that the parents of a child with a sporadic anomaly, previously having an uncomplicated reproductive history and healthy children, tend to avoid cytogenetic examination more often than the carriers of translocation. Hence, the reported proportion of de novo cases (-0.6) might be underestimated. The analysis of pregnancy outcomes in mothers of children with Down syndrome, who inherited translocation (n = 12), sporadic translocation (n = 12) and translocation of unknown origin (n = 8), supports this suggestion. Analysis of the data from 8 reports, where the origin of Dq;21 was specified, revealed that in those samples, where the origin was traced in almost all families, the proportion of de novo cases (0.75-0.82) was higher than in samples where an appreciable part of families was not examined (0.46-0.73). Therefore, with the aim of correct determination of mutation rate for Dq;21 translocation, the true proportions in D;21 cases merit evaluation. Meanwhile, using average estimation from all the above mentioned reports (0.67), the mutation rate for translocations Dq;21 in St. Petersburg was calculated to be 1.2 x 10(-5) and 0.8 x 10(-5) in 1980-1989 and 1990-1999, respectively. For Gq;21 translocations/isochromosomes, the corresponding figures were 1.6 x 10(-5) and 1.5 x 10(-5).     

On the mutation rate of neurofibromatosis.

A genetic study of 124 cases of neurofibromatosis was performed. The contingent of probands was mainly represented by a Russian population, most of the individuals being born in the European part of the RSFSR. Both parents of the probands were examined in only 58 cases, the proportion of sporadic cases in this group being 0.79, as compared to 0.77 for the whole group under study. The existing data evaluated by a direct method are not yet sufficient for a decisive estimation of the penetrance, which, however, cannot be under 80%. Segregation analysis of descendants from particular marriages showed a good correspondance to the hypothesis of Mendelian dominance (32 affected children out of 65). These results analyzed together with those obtained by other authors permit an inference on the full penetrance of neurofibromatosis. The genetic interpretation of sporadic cases as a result of new mutations is presented. The prevalence of neurofibromatosis among the 16-year-old youths was evaluated as 12.8 with 10-(5). This value is suggested to be an estimation of the incidence of the condition in the general population, the mutation rate evaluated by a direct method being equal to 4.4 with 10-(5) divided by 4.9 with 10-minus 5. The increased birth order of probands in sporadic cases (against the theoretical expectation) as well as increased paternal age (as compared with controls) were found to be statistically significant (P equals 0.004 and P equals 0.03, respectively) while the difference in maternal ages was statistically insignificant (P equals 0.008). No statistical relationship between sporadic cases and occupational exposure of parents to deleterious chemical and physical factors was found.     

Analysis of structural and numerical chromosome abnormalities in sperm of normal men and carriers of constitutional chromosome aberrations. A review

Sperm chromosome analysis offers the opportunity to gather information about the origin of chromosome aberrations in human germ cells. Over the last 20 years more than 20 000 sperm chromosome complements from normal donors and almost 6000 spermatozoa from men with constitutional chromosome aberrations (inversions, translocations) have been analyzed for structural and numerical chromosome abnormalities, as well as for segregation of the constitutional chromosome aberrations after the sperm had penetrated hamster oocytes. On the other hand, it took only 6 years to screen more than 3 million mature spermatozoa from healthy probands for disomy rates of 20 autosomes (chromosomes 19 and 22 not evaluated) and the sex chromosomes, and for diploidy rates by in situ hybridization techniques. In the present paper the results arising from both methods are compiled and compared. Received: 29 January 1997 / Accepted: 5 March 1997     

Mutation rates for unbalanced Robertsonian translocations associated with Down syndrome. Evidence for a temporal change in New York State live births 1968--1977.

The mutation rate for translocation Down syndrome was investigated for New York State live births for each of the years 1968--1977 using data from the New York State Chromosome Registry. The overall rate was 2.5 X 10(-5) per gamete (1.4 X 10(-5) for G/21 and 1.0 X 10(-5) for D/21 rearrangements), about 20% higher than rates previously reported by two other studies. For the first 5-year period, 1968--1972, the rate was 1.8 X 10(-5), and for the second 5-year period, 3.1 X 10(-5); there was an abrupt change in 1973 and 1974 to rates more than twice that in the 3 preceding years. These rates were derived by applying completeness estimates for all cases of Down syndrome, mostly 47,trisomy 21, in the jurisdiction to cases with translocation Down syndrome mutations. If completeness corrections are ignored and only the minimum boundaries of rates are considered, however, the increase in 1973 and 1974 was even greater compared with the previous 3 years. The trends, if not attributable to an undetected artifact, may have been caused by an increased frequency of mutant zygotes and/or enhanced intrauterine survival of mutant translocations.     

Neurofibromatosis-1: a maximum likelihood estimation of mutation rate

Summary Methods of classical segregation analysis were applied to a sample of 129 sibships with one or more individuals affected by neurofibromatosis-1 (NF-1). The sample consists only of subjects with NF-1; all the probands had been referred for genetic counselling because of café-au-lait spots, and a diagnostic protocol was invariably applied. No deviation from the segregation ratio expected for a fully penetrant Mendelian dominant gene was observed. A maximum likelihood estimate of the proportion of sporadic cases was obtained, and the mutation rate was estimated to be 6.5×10^-5 gametes per generation (95% CI 5.0–8.1).     

A hypothesis: radiation-related leukemia is mainly attributable to the small number of people who carry pre-existing clonally expanded preleukemic cells

Human leukemia frequently involves recurrent translocations. Since radiation is a well-known inducer of both leukemia and chromosomal translocations, it has long been suspected that radiation might cause leukemia by inducing specific translocations. However, recent studies clearly indicate that spontaneous translocations specific to acute lymphocytic leukemia (ALL) actually occur much more frequently than do leukemia cases with the same translocations. Moreover, the ALL-associated translocation-bearing cells are often found to have clonally expanded in individuals who do not develop ALL. Since radiation-induced DNA damage is generated essentially randomly in the genome, it does not seem likely that radiation could ever be responsible for the induction of identical translocations of relevance to ALL in multiple cells of an individual and hence be the primary cause of radiation-related leukemia. An alternative hypothesis described here is that the radiation-related ALL risk for a population is almost entirely attributable to a small number of predisposed individuals in whom relatively large numbers of translocation-carrying pre-ALL cells have accumulated. This preleukemic clone hypothesis explains various known characteristics of radiation-related ALL and implies that people who do not have substantial numbers of preleukemic cells (i.e. the great majority) are likely at low risk of developing leukemia. The hypothesis can also be applied to chronic myelogenous leukemia and to young-at-exposure cases of acute myelogenous leukemia.     

A Drosophila model of improving the fitness of translocations for genetic control

Summary Translocations with euchromatic breakpoints were generated in lethal-free autosomes of Drosophila melanogaster. Pairs of initially homozygous-lethal translocations, matched for one breakpoint, were allowed to recombine for ten generations. At the end of the experiment, 10/47=21% of crosses (representing 8/26=31% of the intial translocations) had at least one line with at least one homokaryotypic third-instar larva, detected among a small sample of salivary gland preparations from each cross. Among these ten crosses, chromosome extractions were performed; 5/10 of the crosses (probably representing 4/8 of the translocations) had at least one chromosome set with relative viability greater than 15%–25%. To a first (and conservative) approximation, 5/47=11% of crosses showed improvement of viability of 1 of the translocations in the cross during the controlled recombination regime; overall, 4 of the 26 translocations (15%) showed improvement of viability. Partly because of the conservative criterion of viability used, this figure is less than the 20% of translocations that theoretically should be improvable. Pseudohomokaryotypes (pairs of translocations with both breakpoints nearly matching) did not behave as very fit homokaryotypes. However, some of them generated viable hyperploid assortment products that might be of practical interest to mask deleterious effects at breakpoints of translocations. The improvement of fitness of at least a proportion of low fitness translocation stocks by the use of a controlled recombination procedure should be feasible for many pest species.     

Chromosome labeling with transposable elements in maize

Transposable elements randomly insert into a targeted locus at a frequency of 10^-6 to 10^-5. The En element has been shown in previous studies to transpose more frequently into closely linked sites. Thus, it is appropriate to place an En element onto each of the 20 chromosome arms in maize to maximize tagging efficiency. This is called chromosome labeling for tagging purposes with transposons. After a chromosome arm has been labeled with a transposon, genes residing in that arm will have a greater chance to be tagged by the transposon. To date, all of the maize chromosome arms have been labeled with at least one of five Encontaining alleles. The elements were linked to the arms using reciprocal translocations. The usage of these arm-labeled lines is discussed in the context of gene tagging.Journal Paper No. 15224 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa; Project No. 3176     

Case-control study of whether subfertility in men is familial.

OBJECTIVE--To test the hypothesis that subfertility in men is familial and to examine the distribution of subfertility within families for consistency with a genetic cause. DESIGN--Case-control study and segregation analysis. SETTING--Two teaching hospitals in Leeds. SUBJECTS--Cases (probands) were men with an abnormal sperm count who attended a subfertility clinic and whose partners had no major factor contravening fertility. Controls were fathers of two or more children recruited through vasectomy clinics or a maternity department. MAIN OUTCOME MEASURES--The incidence of involuntary childlessness among brothers with partners and among sisters and second and third degree male relatives. When possible clinical and laboratory details were obtained from involuntarily childless brothers. RESULTS--Seventeen of the 148 (11.5%) brothers of probands but none of the 169 brothers of controls had sought medical advice for childlessness (P < 0.0005). Four probands had more than one involuntarily childless brother. There were six further brothers whose childlessness was thought to be involuntary bringing the total prevalence of subfertility among brothers of probands to 16%. Segregation analysis was consistent with an autosomal recessive mode of inheritance accounting for 60% of subfertility in men. Seventeen of the 346 (4.9%) uncles of probands and 10 of 420 (2.8%) uncles of controls were reported to be involuntarily childless (P = 0.09), but there was no difference in childlessness among sisters. In three families sperm counts from "affected" brothers confirmed the diagnosis and showed considerable similarities within but not between families. CONCLUSION--Subfertility in men has a familial component, and the observations are consistent with an autosomal recessive mode of inheritance in over half the cases. Several different genes are probably involved.     

Disease associated balanced chromosome rearrangements (DBCR): report of two new cases

Disease associated balanced chromosome rearrangements (DBCR) causing truncation, deletion, inactivation or over-expression of specific genes are instrumental in identifying and cloning several disease genes and are estimated to be much more common than anticipated. In one survey, the minimal frequency of combined balanced de novo reciprocal translocations and inversions causing abnormal phenotype is estimated to be 0.17%, a sixfold increase compared to the general population suggesting a causative linkage between the abnormality and the observed phenotypic traits. Here, we report two new cases of apparently balanced de novo translocations resulting in developmental delay and dysmorphic features.     

Chromosome translocations: study of 232 cases originating from 144 families

Between 1974 and 1987, 232 translocation carriers have been detected in our Center; they belong to 144 different families. Indications for chromosome analysis were the following: familial studies in relation with a patient suggesting a chromosome anomaly (25.4%); mental retardation with or without malformations (24.6%); 2 or more spontaneous abortions (17.2%); infertility problems, mainly male (16.4%); genetic counseling for a non-chromosomal disease (9.5%); prenatal diagnosis in risk pregnancies (6.9%). The chromosome anomalies detected were the following; balanced Robertsonian fusions (114 cases = 49.1%); balanced translocations (74 cases = 31.9%); unbalanced translocations, Robertsonian fusions included (44 cases = 19%). Two groups may be distinguished: the first one confirms data already known, such as high frequency of balanced translocations in couples with multiple abortions, or in infertile males. The second group on the contrary shows more unusual observations: 4 cases of standard trisomy 21 born to young parents carriers of a balanced translocation not involving chromosome 21; 5 cases of trisomy 13 with 46 chromosomes and a Robertsonian fusion, born to parents carriers of a t(13q; Dq) (twice the mother and thrice the father); 14 cases of apparently balanced translocations, however with an abnormal phenotype; and finally 22 cases of balanced translocations incidentally detected during the course of investigations in patients with a genetic problem generally not associated with a chromosome defect.     

Pericentric inversions in man: personal experience and review of the literature

Summary The Leuven cytogenetic centre experience on pericentric inversion in man is discussed with exclusion of the pericentric inversions of the heterochromatic blocks of chromosomes 1 and 9. In a total of 51,500 patients, referred for constitutional chromosome analysis during the period 1970–1985, pericentric inversions were found in 24 index patients. The breakpoints detected in these different pericentric inversions are summarized and compared to those found in previous reports. Bands 2p13, 2q21, 5q31, 6c21, 10q22, and 12q13 were shown to be repeatedly involved in the different studies and, furthermore, breakpoints at bands 2q11, 5p13, 5p15, 5q13, 7q11, 11q25, and 14p11 were present in this study as well as in our previous review on reciprocal autosomal translocations. In 13 familial pericentric inversions, even after exclusion of all inversion carrier probands, a 1.6:1 excess of pericentric inversion carriers versus karyotypically normal progeny was observed. While chromosomally unbalanced offspring represent 3.5% of all chromosomally investigated liveborns of the present study, 7.1% of all liveborn inversion carrier offspring presented with a mental retardation and/or multiple congenital anomalies (MR/MCA) problem. Additional chromosomal abnormalities, i.e. a 21 trisomy and an accessory small ring chromosome were observed in two pericentric inversion carriers. These data and results are discussed and compared to the data available in the literature.     

Rearrangements of chromosome 9 in different hematological neoplasias

In the present article the frequency of anomalies in chromosome 9 among children with hematological neoplasias amounted to 25/112 in acute lymphoblastic leukemia (ALL), 10/83 in acute myeloid leukemia (AML), and 3/20 in myelodysplastic syndrome (MDS). In ALL, deletions are encountered more often than translocations. Deletions are found in both single anomalies and as an element in complex karyotypes. The rearrangements involve the bands 9q34 and 9q22 the most often. The translocation t(9;22)(q34; q11) is encountered in 7.1% of all cases of ALL. In AML, translocation are found more often than deletions. Structural rearrangements most often involved the long arm, at bands 9q22 and 9q34. Deletions, duplications, and translocations were recorded in MDS. No relationship with the initial hematological indicators, including blastosis, were found. The studies attest to different directions of the clinical prognosis in the course of acute leukemia (AL) where there are deletions. Multidrug resistance and the continuing progress of the disease in the course of chemotherapy is found in t(9;22)(q34; q11).