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1.
Three embryos of Locusta migratoria are described which are mosaics of haploid and diploid cells. The chromosome constitution of the diploid cells discounts the possibility of a parthenogenetic origin. Polyspermy or polar body activation appear to be the most likely mechanisms of production.  相似文献   

2.
In this study, we address the relationship between motility and genetic content of mouse sperm. The chromosome complements of highly motile mouse sperm, selected using the swim-up technique, were analyzed after in vitro fertilization, at the first cleavage state. They were compared to those of unselected sperm. Identification of male and female chromosome sets was possible because of their differential condensation at the first mitotic division. In vitro fertilization, swim-up separation, chromosome preparation, and staining were carried out using standard techniques. The results indicate that highly motile mouse sperm did not differ in types and frequencies of chromosomal abnormalities from those not selected for motility. Moreover, separation of motile sperm does not deviate the sex ratio from the theoretical 1:1.  相似文献   

3.
A study was made of the chromatin structure of mature sperm cells from healthy males aged 25 to 40 using fluorescent microscopy and acridine orange staining according to the DNP cell thermal denaturation technique modified by the authors. It was shown that normal human sperm cell chromatin melting profiles represent uniform curves with maxima in the following temperature ranges: 43 (+/- 2) degrees, 55 (+/- 1) degrees, 67 (+/- 2) degrees, 77 (+/- 1) degrees, 82 (+/- 0.5) degrees, 89 (+/- 1) degrees, 92 (+/- 2) degrees (P less than 0.01), that are identical to those obtained with lymphocytes of healthy males with certain deviations from the standard normal variant. No heteromorphism was revealed in the sperm cell chromatin. Marked polymorphism in the chromatin structure occurs but at the diploid cell level. A 10-time decrease in the fluorescence of AO bound with sperm cell chromatin as compared to F530 AO bound with lymphocyte chromatin structure of the same individual supports the data on the over condensation of sperm cell nuclear chromatin as compared to that in lymphocytes.  相似文献   

4.
The lack of a paternal genome in parthenogenetic embryos clearly limits their postimplantation development, but apparently not their preimplantation development, since morphologically normal blastocysts can be formed. The cleavage rate of these embryos during the preimplantation period gives a better indication of the influence of their genetic constitution than blastocyst formation. Conflicting results from previous studies prompted us to use a more suitable method of following the development of haploid and diploid parthenogenetic embryos during this period. Two classes of parthenogenetic embryos were analysed following the activation of oocytes in vitro with 7% ethanol: 1) single pronuclear (haploid) embryos and 2) two pronuclear (diploid) embryos. Each group was then transferred separately during the afternoon to the oviducts of recipients on the 1st day of pseudopregnancy. Control (diploid) 1-cell fertilised embryos were isolated in the morning of finding a vaginal plug, and transferred to pseudopregnant recipients at approximately the same time of the day as the parthenogenones. Embryos were isolated at various times after the HCG injection to induce ovulation, from each of the three groups studied. Total cell counts were made of each embryo, and the log mean values were plotted against time. The gradient of the lines indicated that 1) the cell doubling time of the diploid parthenogenones was 12.25 +/- 0.34 h, and was not significantly different from the value obtained for the control group (12.74 +/- 1.17 h), and that 2) the cell doubling time of the haploid parthenogenones (15.25 +/- 0.99 h) was slower than that of the diploid parthenogenones and the control diploid group.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

5.
Reliable estimation and improvement of the developmental potential of in vitro production (IVP) embryos requires functional criteria of embryo quality. Antiapoptotic and mitogenic effects of insulin-like growth factor I (IGF-I), applied during bovine IVP, were studied. Day 6.5 blastocysts were fixed and processed for TUNEL to detect apoptotic cells, for immunocytochemical detection of proliferating cell nuclear antigen (PCNA), and for propidium iodide (PI) staining to detect all nuclei. Laser scanning confocal microscopy was used to determine apoptotic (TUNEL/PI) and proliferative (PCNA/PI) indices. Addition of IGF-I to the culture but not to the maturation medium increased the morula/blastocyst yield (P = 0.03), but the cleavage rate was not affected. During culture, IGF-I significantly lowered the apoptotic index by decreasing the number of apoptotic cells per embryo and elevated the total cell number of the blastocysts. The frequency of blastocysts with apoptotic cells was not affected. IGF-I increased the proportion of blastocysts with apoptotic cells in the inner cell mass area only by reducing apoptosis in the trophectoderm area. The PCNA index was not affected by IGF-I. A positive correlation observed between apoptotic and PCNA-positive cells was significant in groups stimulated with IGF-I during in vitro culture. Of TUNEL-positive cells, 30%-40% per embryo were also positive for PCNA. This colocalization may indirectly suggest an activation of DNA repair process in TUNEL-positive cells in response to DNA fragmentation. IGF-I reduces apoptosis in bovine IVP embryos. The requirement of IGF-I is more critical during embryo culture than during oocyte maturation. Our data suggest that an assay for TUNEL in conjunction with cell proliferation analysis can provide useful information about the quality of IVP embryos.  相似文献   

6.
7.
We have isolated a mutant ofSchizosaccharomyces pombe whose growth is temperature sensitive when it is haploid but not when it is diploid. This mutant may provide a useful system for selecting nonconditional mutants which are defective in diploid formation upon conjugation.  相似文献   

8.
Saccharomyces cerevisiae was grown in a rich medium under the conditions of "quasi-continuous" cultivation and, after 200-300 generations, its diploid cells almost completely displaced haploid cells from the original mixed "haploid-diploid" population where the ratio between diploid and haploid strains was either 1:1 or 1:100. The cultivation at 40 degrees C did not change the relative competitive ability of haploids and diploids. When cells were cultivated in a rich medium at 6 degrees C or in a minimal medium at 30 degrees C, none of the strains showed an advantage over others for about 200 generations. Haploid cells had an advantage over diploid cells during "quasi-continuous" growth in the minimal medium at 30 degrees C. When the temperature was elevated to 40 degrees C, diploid cells displaced haploid cells from the mixed population. No advantage was found for diploid or haploid cells grown in a medium with an elevated KCl content (1.5 M). Haploid cells had an advantage over diploid cells when Pichia pinus was cultivated in a minimal medium. The results are discussed using the hypothesis about the diploid phase being fixed in the course of biological evolution.  相似文献   

9.
10.
Survival and repair of DNA following ultraviolet (254-nm) radiation have been investigated in ICR 2A, a cultured cell line from haploid embryos of the grassfrog, Rana pipiens. Survival curves from cells recovering in the dark gave mean lethal dose value (Do) in the range 1.5--1.7 Jm-2 for both haploid and diploid cell stocks. The only significant difference observed between haploids and diploids was in the extent of the shoulder at low fluence (Dq), the value for exponentially multiplying diploid cells (3.0 Jm-2) being higher than that found for haploids (1.2 Jm-2). Irradiation of cultures reversibly blocked in the G1 phase of the cell cycle gave survival-curve coefficients indistinguishable between haploids and diploids. Post-irradiation exposure to visible light restored colony-forming capacity and removed chromatographically estimated pyrimidine dimers from DNA at the same rates. After fluences killing 90% of the cells, complete restoration of survival was obtained after 60-min exposure to 500 foot-candles, indicating that in this range lethality is entirely photoreversible and therefore attributable to pyrimidine dimers in DNA. Dimer removal required illumination following ultraviolet exposure, intact cells and physiological temperature, implying that the photoreversal involved DNA photolyase activity. Excision-repair capacity was slight, since no loss of dimers could be detected chromatographically during up to 48 h incubation in the dark and since autoradiographically detected "unscheduled DNA synthesis" was limited to a 2-fold increase saturated at 10 Jm-2. These properties make ICR 2A frog cells useful to explore how DNA-repair pathways influence mutant yield.  相似文献   

11.
To obtain insights into the mechanisms of spontaneous mutations in Saccharomyces cerevisiae, we have characterized the genetic alterations that inactivate either the CAN1 gene in haploid cells or heterozygously situated in diploid cells. The mutation rate in haploid cells was 9.08 x 10(-7), 100-fold lower than that in diploid cells (1.03 x 10(-4)). In haploid cells, among 69 independent CAN1 mutations, 75% were base substitutions and 22% frameshifts. The base substitutions were both transitions (33%) and transversions (42%), with G:C-->A:T and G:C-->T:A dominating. Minus frameshifts (12%) and plus frameshifts (10%) were also observed at run and non-run bases, and at A:T and G:C pairs with almost equal efficiency. An analysis of chromosome structure in diploid yeast cells indicated that allelic crossover was the predominant event followed by gene conversion and chromosome loss. We argued that genetic alterations leading to spontaneous phenotypic changes in wild-type diploid yeast cells occurred through two steps; replication-dependent alterations of bases in either allele then recombination-dependent transfer of the mutated allele to the intact one.  相似文献   

12.
 Deterministic models of mutation and selection in the space of (binary) nucleotide-type sequences have been investigated for haploid populations during the past 25 years, and, recently, for diploid populations as well. These models, in particular their ‘error thresholds’, have mainly been analyzed by numerical methods and perturbation techniques. We consider them here by means of bifurcation theory, which improves our understanding of both equilibrium and dynamical properties. In a caricature obtained from the original model by neglecting back mutation to the favourable allele, the familiar error threshold of the haploid two-class model turns out to be a simple transcritical bifurcation, whereas its diploid counterpart exhibits an additional saddle node. This corresponds to a second error threshold. Three-class models with neutral spaces of unequal size introduce further features. Such are a global bifurcation in haploid populations, and simple examples of Hopf bifurcations (as predicted by Akin’s theorem) in the diploid case. Received 13 June 1995; received in revised form 26 July 1996  相似文献   

13.
Summary Five haploid plants of wheat were used for anther culture. Embryos were formed and six plants were regenerated. Of these, two were haploid (n=3x=21) and two diploid (2n=6x=42). The two diploids derived from the anthers of the same haploid wheat plant gave seeds, but the fertility was reduced in one of them showing, abnormalities at meiosis.  相似文献   

14.
Land plants possess a multicellular diploid stage (sporophyte) that begins development while attached to a multicellular haploid progenitor (gametophyte). Although the closest algal relatives of land plants lack a multicellular sporophyte, they do produce a zygote that grows while attached to the maternal gametophyte. The diploid offspring shares one haploid set of genes with the haploid mother that supplies it with resources and a paternal haploid complement that is not shared with the mother. Sexual conflict can arise within the diploid offspring because the offspring's maternal genome will be transmitted in its entirety to all other sexual and asexual offspring that the mother may produce, but the offspring's paternally derived genes may be absent from these other offspring. Thus, the selective forces favouring the evolution of genomic imprinting may have been present from the origin of modern land plants. In bryophytes, where gametophytes are long-lived and capable of multiple bouts of asexual and sexual reproduction, we predict strong sexual conflict over allocation to sporophytes. Female gametophytes of pteridophytes produce a single sporophyte and often lack means of asexual reproduction. Therefore, sexual conflict is predicted to be attenuated. Finally, we explore similarities among models of mate choice, offspring choice and segregation distortion.  相似文献   

15.
16.
Desoxyribose nucleic acid in embryonic diploid and haploid tissues   总被引:2,自引:0,他引:2  
MOORE BC 《Chromosoma》1952,4(6):563-584
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17.
Betty C. Moore 《Chromosoma》1950,4(1):563-576
Summary Nuclear DNA values were determined by the cytochemical photometric method for various tissues of diploid and haploid Rana pipiens embryos. It was found that the ratio of diploid to haploid amounts of nuclear DNA was approximately two to one.The major interest of this study lies in the demonstration of a wide range of nuclear DNA values and the correlation of changes in this range with progressive differentiation. Older, more differentiated tissues were found to have a narrower range of DNA values than younger, less differentiated tissues.Evidence is cited that such differences in DNA values are real biological variations and the results are discussed in relation to differentiation.  相似文献   

18.
We have isolated a mutant ofSchizosaccharomyces pombe whose growth is temperature sensitive when it is haploid but not when it is diploid. This mutant may provide a useful system for selecting nonconditional mutants which are defective in diploid formation upon conjugation.  相似文献   

19.
The electrophoretic mobility of diploid cells, haploid cellsof different mating types, their cell walls, asci, and ascosporesof Saccharomyces cerevisiae was measured with a free-flow electrophoreticapparatus. Haploid -cells and ascospores exhibited higher mobilitythan diploid cells, haploid -cells, and asci. Similar differencesin mobility were found with isolated cell walls of the haploidand diploid cells. 2 Present address: Lederle (Japan) Ltd., Kyobashi, Tokyo 104,Japan. (Received December 24, 1976; )  相似文献   

20.
Chromosome counts were obtained from 73 out of 177 (41%) early cleavage-stage Merino embryos. A further 13 embryos were classified as probably diploid. Chromosome aberrations were found in 8 (11%) embryos, one of which was aneuploid and the remainder (9.6%) had euploid abnormalities. If the probable diploid embryos are included, the incidence of euploid aberrations falls to 8.1%. Of the abnormal embryos there was one aneuploid with 2N = 55, two haploids, four haploid/diploid mosaics and one zygote with 4 haploid metaphase plates. Two additional zygotes had 4 interphase pronuclei. Four of the euploid abnormalities were attributable to the entry of two or more spermatozoa and therefore polyspermy is the largest single factor leading to chromosomally aberrant embryos in this population of Merino ewes.  相似文献   

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