Frequency Of Aneuploids Research Articles

Хромосомна нестабільність чистопородних і кросбредних корів молочного напряму продуктивності

The article presents the results of research on the karyotype characteristics variability in purebred and crossbred dairy cows. The material for the research was peripheral blood samples of purebred firstborn cows of the Ukrainian red-spotted dairy and Ukrainian black-spotted dairy breeds, as well as crossbred cows obtained from crossing Ukrainian red-spotted with Montbeliard bulls (DG “Nyva” SE of the Institute of Animal Breeding and Genetics named after M. V. Zubets NAAS. Preparation of cytogenetic preparations, analysis of morphology, identification and classification of chromosome aberrations were carried out according to generally accepted methods. We performed cell analysis with the Axiostar plus microscope (Carl Zeiss, Germany) under immersion magnification of 1000 times and took microphotographs. In all studies, the frequency of aberrant metaphases and the spectrum of chromosomal aberrations were determined as parameters of chromosomal instability. The following signs were taken into account: the frequency of aneuploid and polyploid cells, cells with premature separation of the centromeric regions of chromosomes (CRC), cells with structural aberrations of chromosomes (breaks, fragments and associations of non-homologous chromosomes). As a result of the analysis of karyotypes of firstborn cows of purebred and crossbred origin, it was established that the proportion of diploid cells in the norm is on average 85%. The remaining almost 15% are somatic cells with numerical and structural abnormalities. Crossbred cows have significantly higher frequencies (P<0.001) of aneuploid (one and a half times), polyploid (by 27%), structural aberrations of chromosomes (by 20%) than in purebred cows of the Ukrainian red-spotted and black-spotted dairy breeds. 15–20% more cells containing chromosomes with breaks and fragments were also found in crossbred firstborns. The results of the cytogenetic study indicate greater chromosomal instability in crossbred cows compared to purebred cows. One of the reasons for this phenomenon may be the influence of breeding methods, in particular crossbreeding.

CHROMOSOMAL PROFILE OF LARGE WHITE AND LAND BREED PIGS

This article presents the results of studies of karyotypic variability of pigs of two breeds - large white and landrace.The research was carried out in the Department of Animal Genetics and Biotechnology of the Institute of Animal Breeding and Genetics named after M.V. Zubtsia of the National Academy of Sciences. Karyotype analysis was performed on preparations of metaphase chromosomes obtained from peripheral blood lymphocytes according to the generally accepted method. The following cytogenetic indicators were included in the analysis: the frequency of aneuploid and polyploid cells, the frequency of cells with structural aberrations of chromosomes. Statistical processing of experimental data was carried out using Office Excel 2003.A comparative analysis of the karyotypes of two groups of pigs of the Great White and Landrace breeds shows the statistical reliability of the difference between the experimental groups of pigs in terms of the frequency of aberrant cells.The spectrum of numerical violations of the karyotype in all groups is represented by poly- and aneuploid cells. A higher frequency of polyploid cells is observed in pigs of the landrace breed compared to individuals of the large white breed.Almost twice as many aneuploid cells were recorded in landraces than in large white pigs).Analysis of the karyotypes of the studied groups of pigs revealed various chromosomal aberrations - associations and translocations of chromosomes, chromosomal breaks and fragments. Chromosome breaks in both groups of examined pigs occur with the same frequency - almost 3%. In the karyotypes of individual sows, we found two different centric fusions of chromosomes: in sow No. 7659 of the landrace breed, a Robertsonian translocation of rob 15/17, and in sow No. 2817 of the Big White breed, an association of chromosomes 16 and 17. These pigs were diagnosed with a reduced level of reproductive capacity, the cause of which, obviously, is a violation of the separation of chromosomes in meiosis. Among the studied animals, we did not find individuals with reciprocal translocations.In our study, in landraces, the frequency of premature separation of the centromeric regions of chromosomes in mitosis is 35,5% more frequent than in individuals of a large white breed, which indicates an unbalanced genotype of the animals of this studied group and indicates the peculiarities of selection work with them.The analysis of the pedigrees of the sows that were selected in the group for this study confirmed this assumption: the animals were obtained by interbreeding.Almost twice the frequency of polyploid cells confirms their belonging to animals of the meat type of productivity.Therefore, the analysis of polymorphism of karyotypic traits of pigs of the two studied groups of pigs of the Great White and Landrace breeds shows that the cytogenetic parameters of the studied pigs vary in the following range: the frequency of aberrant cells - from 5.11±0.05 to 7.63±0.17; frequency of polyploid cells - from 4.50±1.6 to 7.84±2.6; aneuploid - from 3.0±1.8 to 5.6±2.9; the frequency of chromosome breaks is from 2.8±1.3 to 2.9±1.7. It is obvious that the level of chromosomal instability is dominated by landrace pigs, the reason for which, in our opinion, is the peculiarities of breeding work with this breed.

Cytogenetic abnormalities in young cattle during vaccination against salmonelloses

The spectrum and the frequencies of cytogenetic abnormalities in young cattle immunized with a vaccine against salmonellosis of calves were investigated. The study was carried out on the farm of Novosibirsk region on 10 clinically healthy Holstein black-and-white calves of 10-17 days of age. A concentrated formol-alum vaccine against salmonellosis (paratyphoid) of calves was used at a dose of 2 ml (reimmunization at a dose of 2 ml) with an interval of 10 days between injections. The vaccine was made from the culture of bacteria of the Salmonella dublin strain № 373, inactivated with formalin with the addition of potassium alum and calcium chloride. Cytogenetic analysis of peripheral blood in calves was carried out before vaccination (control), 2 and 9 days after vaccination, 2 and 9 days after revaccination. It was found that the spectrum of somatic chromosomal instability in peripheral blood lymphocytes of calves after vaccination and revaccination is represented by polyploidy, hypoploidy and hyperploidy, chromatid and chromosomal breaks, single and paired fragments of chromosomes. It was revealed that the spectrum of somatic chromosomal instability after double immunizations with an inactivated vaccine against salmonellosis did not differ from the spectrum of spontaneously occurring mutations in this species. Vaccination and subsequent revaccination of calves in comparison with the pre-vaccination period did not lead to a significant increase in the frequency of aneuploid and polyploid cells. During double immunization of calves, a wave pattern in the variation of genomic mutation frequencies from maximum to minimum values in the lymphocytic blood cells of animals was noted, similar to prolonged mutagenesis. A tendency was found for the frequency of structural chromosome abnormalities to increase 2 and 9 days after vaccination and 2 days after revaccination. There was a credible 2.9-fold increase in the frequency of cells with chromosomal aberrations in the blood lymphocytes of animals 9 days after their repeated immunization due to breaks and paired fragments of chromosomes. After vaccination and revaccination, chromatid breaks were most often recorded in the medial regions of one of the chromatids, and chromosomal breaks in the medial and telomeric regions of both chromatids.

Advanced sperm testing.

The sensitivity of semen analysis for detection of infertility remains low. Many factors not measured in traditional semen analysis may contribute to male factor infertility. DNA fragmentation, oxidative stress, and sperm aneuploidy are three factors that may contribute further information to the evaluation when semen analysis is inconclusive. DNA fragmentation measures the destruction of and failure to repair damage to DNA. Increased DNA fragmentation has been used as a marker for oxidative stress as well as toxic exposure. The oxidative stress adduct measures DNA aberrations, which sperm cannot repair and has been used to support use of antioxidants. Lastly, the aneuploid sperm frequency is a quantitative measure of deviation from the normal chromosomal complement. Although elevated sperm aneuploid frequency has been associated with recurrent pregnancy loss and implantation failures, barriers remain to its routine use. We identified these three adjunctive tests, which have the potential to alter either management or counseling of patients with regards to male factor infertility. Elevated DNA fragmentation or significant sperm aneuploidy may suggest the need for further investigation or further preimplantation genetic testing prior to IVF. The oxidative stress adduct may lend further explanation and improved counseling of the infertile patient.

Synthetic polyploids in Vicia cracca: methodology, effects on plant performance and aneuploidy

The comparison of natural and synthetic polyploids helps understand the consequences of polyploidization and separate the effects of genome duplication from subsequent evolution. The method has, however, been used only in a limited number of ecological studies, and we know little about its possible limits. We optimized methodology to produce synthetic polyploids in Vicia cracca and explored the differences in stomata size, time to germination and plant size between synthetic and natural polyploids and diploids. We also explored variation in relative genome size and chromosome number of synthetic polyploids and attempted to understand consequences of this variation on plant performance. The creation of synthetic polyploids was possible even though it was met with relatively low success. Stomata length was affected directly by polyploidization. In contrast, plant size was neither a function of polyploidization nor of subsequent evolution. Time to germination increased in synthetic polyploids, suggesting that only subsequent evolution will return the germination rate to the original levels. While the relative genome size of synthetic polyploids fell within the range of natural polyploids, 25% of the synthetic polyploids turned out to be aneuploids. The differences in chromosome number were reflected in performance of the synthetic polyploids. Exclusion of aneuploids from the data, however, did not affect the between-cytotype comparison. A more detailed comparison of the frequency of aneuploids among natural and synthetic polyploids is needed to understand possible differences between synthetic and natural polyploids and the effects of aneuploidy on the conclusions of ecological studies comparing natural and synthetic polyploids.

Highlights from Recent Cancer Literature

Highlights from Recent Cancer Literature

Evidence for Karyotype Polymorphism in the Free-Living Flatworm, Macrostomum lignano, a Model Organism for Evolutionary and Developmental Biology.

Over the past decade, the free-living flatworm Macrostomum lignano has been successfully used in many areas of biology, including embryology, stem cells, sexual selection, bioadhesion and aging. The increased use of this powerful laboratory model, including the establishment of genomic resources and tools, makes it essential to have a detailed description of the chromosome organization of this species, previously suggested to have a karyotype with 2n = 8 and one pair of large and three pairs of small metacentric chromosomes. We performed cytogenetic analyses for chromosomes of one commonly used inbred line of M. lignano (called DV1) and uncovered unexpected chromosome number variation in the form of aneuploidies of the largest chromosomes. These results prompted us to perform karyotypic studies in individual specimens of this and other lines of M. lignano reared under laboratory conditions, as well as in freshly field-collected specimens from different natural populations. Our analyses revealed a high frequency of aneuploids and in some cases other numerical and structural chromosome abnormalities in laboratory-reared lines of M. lignano, and some cases of aneuploidy were also found in freshly field-collected specimens. Moreover, karyological analyses were performed in specimens of three further species: Macrostomum sp. 8 (a close relative of M. lignano), M. spirale and M. hystrix. Macrostomum sp. 8 showed a karyotype that was similar to that of M. lignano, with tetrasomy for its largest chromosome being the most common karyotype, while the other two species showed a simpler karyotype that is more typical of the genus Macrostomum. These findings suggest that M. lignano and Macrostomum sp. 8 can be used as new models for studying processes of partial genome duplication in genome evolution.

Chromosome variation and HMW glutenins in synthetic hexaploid wheats (Triticum turgidumssp.dicoccum/Aegilops tauschii)

Seven synthetic hexaploid wheats (Triticum dicoccum/Aegilops tauschii) were subjected for investigation. Numerical variation of chromosome number in F1 hybrids between three synthetics and common wheat varieties, was recorded. Hexaploid amphiploids (SHW) formed gametes with aneuploid chromosome number at a frequency of 13.2 and 14.8% as male and female parents, respectively. We speculated that the frequency of aneuploids in the generation might depend on variability of BAu- and D-genomes of synthetic parents, and could be used for increasing the genetic diversity in common wheat. The HMW-glutenins analysis divided two lines in SHW530 and 532 due to different genes present in the B-genome, and increased them to 9 synthetic lines. The subunits 1Dx1.5 + 1Dy10 was predominantly observed in the synthetics. Two other allelic variants 1Dx2 + 1Dy11 and 1Dx4 + 1Dy10.1 were found in four lines and appeared as new genes in SHW originated from Aegilops tauschii. The synthetic hexaploid lines could play a significant role as novel germplasm resources for improving the grain quality of bread wheat.

Somaclonal variation in ‘Red Flash’ caladium: morphological, cytological and molecular characterization

Somaclonal variation is a major concern to many applications of plant cell and tissue culture techniques, yet it could be a useful source of variation for plant genetic improvement. High frequencies of somaclonal variants were reported in caladium, but little was known about changes in caladium somaclonal variants at the cellular and molecular levels. Twenty-four somaclonal variants were identified among ‘Red Flash’ caladium plants regenerated from two types of leaf explants and on two media containing different auxins. Results showed that the type of leaf explants and auxin affected the occurrence of somaclonal variants in ‘Red Flash’. The highest percentage of variants (25.0 %) was observed among plants regenerated from mature leaf explants cultured on the media containing 2,4-dichlorophenoxyacetic acid. These somaclonal variants exhibited considerable changes in leaf shape, coloring of the main veins, spots, margins, and leaf size, and could be separated into 10 somaclonal variant groups. Twelve variants contained 1.1–5.4 % less nuclear DNA and appeared to have lost one chromosome. Two variants contained 5.4–9.2 % less nuclear DNA and appeared to have lost two chromosomes. One variant contained 95.0 % more nuclear DNA and 2n = 58 chromosomes. Two SSR markers (CaM1 and CaM103) revealed DNA banding pattern changes in nine variants, including allele loss in eight variants and allele size change in one variant. These results suggested that several cytological and/or molecular causes were involved in the somaclonal variation in ‘Red Flash’ and chromosome number change was a frequent cause leading to a high frequency of aneuploids and marker allele loss. The CaM1-carrying chromosome seemed to be unstable and prone to loss during tissue culture.

Production of Hypo- and Hypertetraploid Seedlings from Open-, Self-, and Cross-Pollinated Hypo- and Hypertetraploid Grape

Seedless grape (Vitis spp.) cultivars with large berries can be developed from hypo- and hypertetraploid seedlings. The low occurrence of hypo- and hypertetraploid seedlings, however, has impeded the breeding of new hypo- and hypertetraploid grape varieties. In order to establish hypoand hypertetraploid seedlings, we examined the chromosome numbers in seedlings of self-, open-, and cross-pollinated hypotetraploid ‘Takao’ and hypertetraploid ‘RB9127K’ grape. Three of the five seedlings (60%) from ‘Takao’ were aneuploid, including one with 74 chromosomes (2n=4x-2) and two with 75 chromosomes (2n=4x-1). In ‘RB9127K’, 26 of the 193 seedlings (13.5%) were aneuploid, including three seedlings with 75 chromosomes (2n=4x-1), 18 with 77 chromosomes (2n=4x+1), and five with 78 chromosomes (2n=4x+2). The high frequency of aneuploids from ‘Takao’ and ‘RB9127K’ grape indicates that meiosis in hypo- and hypertetraploid female parents is prone to segregation error. These results suggest that various hypo- or hypertetraploid seedlings can be successfully produced using hypo- or hypertetraploid grapes as female parents, which can contribute to the development of new seedless grape varieties with large berries.

Delayed Numerical Chromosome Aberrations in Human Fibroblasts by Low Dose of Radiation.

Radiation-induced genomic instability refers to a type of damage transmitted over many generations following irradiation. This delayed impact of radiation exposure may pose a high risk to human health and increases concern over the dose limit of radiation exposure for both the public and radiation workers. Therefore, the development of additional biomarkers is still needed for the detection of delayed responses following low doses of radiation exposure. In this study, we examined the effect of X-irradiation on delayed induction of numerical chromosomal aberrations in normal human fibroblasts irradiated with 20, 50 and 100 cGy of X-rays using the micronucleus-centromere assay. Frequencies of centromere negative- and positive-micronuclei, and aneuploidy of chromosome 1 and 4 were analyzed in the surviving cells at 28, 88 and 240 h after X-irradiation. X-irradiation increased the frequency of micronuclei (MN) in a dose-dependent manner in the cells at all measured time-points, but no significant differences in MN frequency among cell passages were observed. Aneuploid frequency of chromosomes 1 and 4 increased with radiation doses, and a significantly higher frequency of aneuploidy was observed in the surviving cells analyzed at 240 h compared to 28 h. These results indicate that low-dose of X-irradiation can induce delayed aneuploidy of chromosomes 1 and 4 in normal fibroblasts.

Доімплантаційний розвиток ембріонів жінок старшого репродуктивного віку

In order to reveal the influence of genetic component on the early embryo development, the retrospective study of morphokinetic characteristics of 717 embryos subjected to preimplantation genetic testing was conducted. Blastomere biopsy for FISH-based preimplantation genetic screening of 7 chromosomes was performed on the third day of culture, while embryo developmental potential and morphological features at the cleavage and blastulation stage were studied regarding maternal age particularly in the group of younger women and patients older than 36. Results of genetic testing revealed that euploid embryos rate gradually decreased with maternal age comprising 39.9% in young women group and 25.3% of specimen belonging to elder patients. At the cleavage stage, morphological characteristics of aneuploid and euploid embryos didn’t differ significantly regardless of the age of patients that could be accounted for the transcriptional silence of embryo genome till the third day of its development. However, in case of prolonged culture chromosomally balanced embryos rarely faced developmental arrest (in 7.9%) and formed blastocysts half more frequently compared to aberrant embryos (respectively 75.6 versus 49.8%). Nevertheless, no substantial difference was found between blastocyst formation rate among embryos with similar genetic component regardless of the maternal age. Taking into consideration high rate of chromosomally unbalanced embryos specific to patients of advanced maternal age, the relative proportion of aneuplouid blastocysts was significantly higher in this group of embryos. Thus, without genetic screening there is a possibility of inaccurate selection of embryos for women of advanced reproductive age for transfer procedure even in case of prolonged culture. Consequently, increase of aneuploid embryos frequency associated with permanent preimplantation natural selection effectiveness along with the postimplantation natural selection failure may be the cause of elevated risk of chromosomally abnormal child birth for advanced age women after natural conception, as well as after assisted reproduction therapy.

The effects of biological and life-style factors on baseline frequencies of chromosome aberrations in human lymphocytes

Objective: This study investigated the influence of sex and ageing on chromosomal damage and the role of life-style habits on the frequency of chromosomal aberrations (CAs) in peripheral blood lymphocytes (PBLs) of healthy Bosnian subjects. Materials and Methods: Peripheral blood samples were obtained from 100 healthy, unrelated individuals in Bosnia and Herzegovina during 2010 and 2011. Chromosome preparations were made by dropping and air drying and slides were stained with 10% Giemsa solution (pH 6.8). The cytogenetic analysis was carried out in a cytogenetic laboratory in the Department of Biology of the Faculty of Science in Sarajevo. The category of total structural CAs was sub classified as chromosome-type aberrations (CSAs) and chromatid-type aberrations (CTAs) while the category of total numerical CAs was sub classified as aneuploid and polyploid mitoses. All statistical analyses were carried out using Microsoft Excel 2010 (Microsoft Corporation) and the Windows Kwikstat Winks SDA 7.0.2 statistical software package (Texa Soft Cedar Hill, Texas). Results: Cytogenetic analysis revealed the average number of structural CAs was 2.84 and of numerical CAs was 9.56. There was a significant increase in the frequency of chromosome-type aberrations (1.92) compared with chromatid-type aberrations (CTAs) (0.92) and a significant increase in the frequency of aneuploid (8.83) compared with polyploid (0.73) mitoses. Significant positive correlations between age and CTAs in human PBLs were also demonstrated. Additional statistical analysis showed that ageing increase number of numerical CAs in lymphocytes of drinkers. The frequency of structural CAs of females exposed to radiation was significantly greater than in males. Analysis indicates the presence of a positive association between CAs and smoking in younger subjects but a negative correlation between aberrant cells frequencies and alcohol in older drinkers. Conclusion: The results of the study support the conclusion that sex and age, together with life-style habits of individuals as confounding factors can affect spontaneous frequency of CAs especially to CTAs in PBLs that are a biomarker of cancer risk.

Aneuploids in the shrub birch Betula humilis populations in Poland

Shrub birch (<em>Betula humilis </em>Schrk.) is endangered glacial relict growing in natural and drained fens and transitional mires. At present study we examined karyotypes of 103 individuals of <em>B. humilis</em>, collected in six populations from eastern and northeastern Poland. We found 60% of diploid individuals with 2n = 28. The rest of studied plants were aneuploids with 26, 27, 29, 30 and 31 chromosomes in their karyotypes. High frequencies of aneuploids in Polish populations of <em>B. humilis </em>could be a consequence of: (i) hybridization with congeneric species, (ii) stress resulting from range fragmentation, (iii) karyotype instability of individuals with 2n ≠ 28, or (iv) vegetative reproduction.

Cytogenetic investigations in hexaploid Triticale I. Meiosis, aneuploidy and fertility

Significant differences in meiotic irregularities, frequency of aneuploids and fertility were found among eight investigated lines of hexaploid Triticale. The different meiotic irregularities show varying degrees of heterogeneity within lines. Frequency of aneuploids correlates with irregularities of meiosis. Fertility does not correlate with cytological disturbances. This indicates that, in part, genetic factors determine fertility independently of meiotic irregularities.

Frequency of aneuploids in progenies of autotriploid barley,Hordeum vulgare L.

Chromosome counts of 863 progeny plants originating from 68 autotriploid barley plants revealed a considerable variation in chromosome numbers ranging from the diploid number (2n= 14) to 2n= 39. The most frequent groups were plants with 15 and 16 chromosomes each constituting about 27% of all progeny plants. Diploid plants and plants with 1 to 5 extra chromosomes constituted about 85% of the progeny plants. The remaining 15% had chromosome numbers from 20 to 39. Plants with the euploid numbers of chromosomes. 21, 28, and 35, were not more frequent than plants with aneuploid numbers between these groups. The results show that barley, although a diploid species, has a high tolerance for extra chromosomes.

Elimination of wheat and rye chromosomes in a strain of octoploid Triticale as revealed by Giemsa banding technique

The number of rye and wheat chromosomes was investigated in the progeny of octoploid Triticale plants (2n = 56). The strain in question exhibits a high degree of meiotic disturbances resulting in a high frequency of aneuploids. Rye and wheat chromosomes were identified by band patterns obtained after Giemsa staining. This technique was found to be more accurate than previous identification techniques. Chromosomes of both the wheat and rye genomes are missing in aneuploids, roughly in proportion to the number of genomes. Rye chromosomes were not over-represented among the missing ones as was previously believed to be the rule in octoploid Triticale.

Aneuploidy in induced autotetraploid populations of Festuca pratensis, Lolium multiflorum and Lolium perenne

The aneuploid frequencies were determined in two autotetraploid populations of Festuca pratensis, St 839 and Sv 01243. Vegetative and generative properties of euploids, hypoploids, and hyperploids were studied. Before chromosome counts, the seed lots were sieved into five seed size fractions. Chromosome numbers were determined by a modification of conventional root tip squash. Chromosome number varied with seed size. This variation was caused by differences in hypoploid frequencies between the fractions. In St 839 the lightest seeds contained 30% hypoploids and the heaviest ones 2%. In Sv 01243 the hypoploid frequencies varied from 20% to 1%. The total aneuploid frequency in St 839 was 29.3% with a slight predominance of hyperploids. In Sv 01243 the aneuploid frequency was 26.0%, with about equal size of the aneuploid chromosome classes. Vegetative and generative characters were measured. Euploids were superior to aneuploids, and hyperploids to hypoploids in both populations. The effects of aneuploidy were more pronounced on the generative characters. The euploids were heading earlier than the aneuploids. The differences were generally highly significant.

Aneuploidy in induced autotetraploid populations of Festuca pratensis, Lolium multiflorum and Lolium perenne

The aneuploid frequencies were determined in two autotetraploid populations of Festuca pratensis, St 839 and Sv 01243. Vegetative and generative properties of euploids, hypoploids, and hyperploids were studied. Before chromosome counts, the seed lots were sieved into five seed size fractions. Chromosome numbers were determined by a modification of conventional root tip squash. Chromosome number varied with seed size. This variation was caused by differences in hypoploid frequencies between the fractions. In St 839 the lightest seeds contained 30% hypoploids and the heaviest ones 2%. In Sv 01243 the hypoploid frequencies varied from 20% to 1%. The total aneuploid frequency in St 839 was 29.3% with a slight predominance of hyperploids. In Sv 01243 the aneuploid frequency was 26.0%, with about equal size of the aneuploid chromosome classes. Vegetative and generative characters were measured. Euploids were superior to aneuploids, and hyperploids to hypoploids in both populations. The effects of aneuploidy were more pronounced on the generative characters. The euploids were heading earlier than the aneuploids. The differences were generally highly significant.

Aneuploidy in induced autotetraploid populations of Festuca pratensis, Lolium multiflorum, and Lolium perenne III. Performance of plants at different sowing densities in a perennial sward of tetraploid Festuca pratensis

Klinga, K. 1987. Aneuploidy in induced autotetraploid populations of Festuca pratensis, Lolium multiflorum, and Lolium perenne. III. Performance of plants at different sowing densities in a perennial sward of tetraploid Festuca pratensis-Hereditas 106:277–287. Lund, Sweden. ISSN 0018–0661. Received February 6, 1987 The productivity of an induced tetraploid population of Festuca pratensis at different sowing densities displayed a typical yield-density response. There was a positive response in yield with increasing densities only early in the development of the sward. As the time passed, the variations in sowing densities were compensated by an altered growth made by individual plants. The mortality pattern of plants varied among seasons. During the establishing phase of the sward the mortality was not density dependent. The inferior ability of aneuploids to establish in the sward relative to the euploids was diplayed by a higher mortality of aneuploids. As the plants had grown larger, the mortality of plants became density dependent. Competition started to affect the aneuploids earlier in the development of the sward than the euploids, reflected by a differentiated mortality pattern of aneuploids and euploids. The aneuploid frequency in the seed lot was 29.1 %, and in the end of the experiment the aneuploid frequency was reduced to percentages ranging from 7.9% to 15.7%. The lower productivity of the aneuploids affected the yield only at the early stages of the sward development. Later, the surviving aneuploids were too few to influence the total yield.