BLANCA MEIOSIS EPUB DOWNLOAD

We describe a unique example of mosaic autotetraploidy in the meiosis of a . Egozcue S, Blanco J, Vidal F and Egozcue J Diploid sperm and origin of. Meiotic studies using multicolour fluorescent in-situ hybridization (FISH) and was done according to the criteria described previously by us (Blanco et al. MEIOSIS MEIOSIS FORMATION OF HAPLOID GAMETES: Meiosis consists in two consecutive mitotic divisions without DNA replication in.


BLANCA MEIOSIS EPUB DOWNLOAD

Author: Scot Hettinger
Country: Turkmenistan
Language: English
Genre: Education
Published: 5 August 2017
Pages: 849
PDF File Size: 25.72 Mb
ePub File Size: 46.8 Mb
ISBN: 362-1-57541-640-4
Downloads: 62746
Price: Free
Uploader: Scot Hettinger

BLANCA MEIOSIS EPUB DOWNLOAD


However, the abnormal testicular environment of these patients probably resulted in meiotic I non-disjunction, and a certain proportion of post-reductional cells were XY The fact that none blanca meiosis the spermatozoa were XY also suggests the existence of an arrest at the secondary spermatocyte or the spermatid level.

In the XYY patient, most The percentage of XYY pachytenes was A high proportion In this case, the data suggest the existence of an arrest of the abnormal cells at the primary and the secondary spermatocyte or the spermatid level, giving rise to the continuous elimination of abnormal cells in the germ-cell line along spermatogenesis.

The fact that the proportion of diploid spermatozoa was only increased in one of the three cases XXY is also suggestive of an arrest of the abnormal cell lines in these patients. The two apparently non-mosaic patients were, in fact, germ-cell mosaics.

This suggests that the cytogenetic criteria used to define non-mosaic patients may be inadequate; thus, the risk of intracytoplasmic blanca meiosis injection in apparently non-mosaics may be lower than expected.

As a result, these patients often attend infertility clinics, where the incidence of such chromosome abnormalities is very high Egozcue et al.

Roles of CDK and DDK in Genome Duplication and Maintenance: Meiotic Singularities

The development of intracytoplasmic sperm injection ICSI solved the fertility problems of many of these patients, because a blanca meiosis spermatozoon was blanca meiosis to obtain one embryo, and a few spermatozoa often produced enough embryos to obtain a continuing pregnancy.

However, it soon became evident that in ICSI couples the incidence of sex-chromosome abnormalities was slightly, but significantly increased, with respect to controls Liebaers et al.

BLANCA MEIOSIS EPUB DOWNLOAD

Since then, different studies have tried to relate this increase of sex-chromosome anomalies to the behaviour of the sex chromosomes during meiosis in XXY and XYY males. Although in general it has been shown that the proportion of sex chromosome disomies was blanca meiosis in these patients, the mechanisms producing blanca meiosis anomalies are still under discussion Egozcue et al.

So far, most meiotic studies concluded that XXY cells were unable to enter meiosis Kjessler, ; Luciani et al.

BLANCA MEIOSIS EPUB DOWNLOAD

However, other meiotic studies Skakkebaek et al. In XYY males, most meiotic studies blanca meiosis that the extra Y chromosome was lost in the blanca meiosis stages Thompson et al.

However, the incidence and types of disomic spermatozoa in XXY and XYY individuals has been shown to be quite variable.

BLANCA MEIOSIS EPUB DOWNLOAD

The increase in the frequency of disomic spermatozoa could be interpreted as a result blanca meiosis the abnormal segregation of the abnormal cell line during meiosis see references in Tables IV and V or as the result of the effect of an abnormal testicular environment blanca meiosis the segregation of a normal cell line Mroz et al.

In addition, there are many cases of an increased proportion of diploid spermatozoa that is difficult to explain Egozcue et al.

Roles of CDK and DDK in Genome Duplication and Maintenance: Meiotic Singularities

Therefore to try to solve this problem the behaviour of the sex chromosome during meiosis in testicular biopsies from patients with sex chromosome anomalies was analysed.

Materials and methods Patients, sample collection and processing XXY patient This year-old azoospermic sterile male had a lymphocyte karyotype 47,XXY in all the metaphases analysed. XYY patient This year-old sterile patient had an oligoasthenoteratozoospermia.

His lymphocyte karyotype was 47,XYY in all metaphases studied. Testicular biopsies were obtained from the three patients under local anaesthesia and processed as usual Evans et al.

All patients gave their informed consent and blanca meiosis procedure was approved by the ethical committees of the centres involved, where diagnostic testicular biopsies are included in the protocol of study of human male infertility or sterility when indicated.

In the XYY blanca meiosis, a semen sample could also be obtained. The sample was fixed in methanol: In each patient we have assessed the sex chromosome constitution of three different types of cells: Interphase germ cells were clearly distinct from somatic cells because Sertoli nuclei are fusiform and other somatic cells are oval, while germ cell nuclei are round.

Prior to FISH, all samples were analysed under phase contrast, and coordinates of spermatozoa and meiotic figures considered adequate for analysis blanca meiosis noted.

  • DNA Replication Controls: Volume 2 - Google Cărți
  • MEIOSIS by Blanca Toledo on Prezi
  • 1. Introduction