Genetics

Preimplantation genetic diagnosis for chromosome abnormalities

  1. Introduction Preimplantation genetic diagnosis (PGD) is the earliest form of prenatal diagnosis, and usually involves the analysis of a single cell after biopsy from a three-day old embryo created through assisted reproductive techniques (ART), or sometimes the first and second polar bodies of the eggs prior fertilization, also through ART. Because the embryo […]

Cytogenetics of infertility (Genetics)

1. Introduction Infertility is a major problem in human society. Up to 15% of couples at reproductive age have either problems in conceiving or repetitive reproductive failures. Human fertility can be altered by many different factors, some of which are related to defined genetic syndromes or chromosome abnormalities, both in males and females (see Article […]

FISH (Genetics)

Standard or conventional chromosomal banding analysis is limited to actively dividing cells and the resolution is limited to chromosomal aberrations greater than 3 Mb in size. On the other hand, fluorescence in situ hybridization (FISH) has developed into a meaningful and clinically accepted higher resolution method for analyzing the genetic characteristics of cells. Different FISH […]

Comparative genomic hybridization(Genetics)

1. Introduction The history of human cytogenetics spans approximately 130 years from when chromosomes were first observed in plant material by Eduard Strasburger in 1875 and in animals by Walter Flemming in 1879-1889 (Lawce and Brown, 1997). However, the major advances in cytogenetics occurred in the 1950s when colchicine and hypotonic treatments were introduced (Hsu, […]

Cytogenetic analysis of lymphomas (Genetics)

1. Introduction Historically, the application of cytogenetic analysis to the investigation of malignant lymphoma has provided the entry point for the identification of critical gene deregulations associated with specific subtypes of B- and T-cell malignant lymphomas (see Article 14, Acquired chromosome abnormalities: the cytogenetics of cancer, Volume 1). These include the IGH-MYC gene fusion created […]

Human sperm – FISH for identifying potential paternal risk factors for chromosomally abnormal reproductive outcomes (Genetics)

1. Introduction A substantial challenge in the identification of human germ cell mutagens is to classify offspring carrying inherited genetic defects, to identify the responsible parent who transmitted the defect, and to determine whether specific genetic defects were caused by prefertilization exposure to environmental, occupational, medical, or other agents. The relatively large baseline frequencies of […]

Imprinting and epigenetic inheritance in human disease (Genetics)

1. Introduction According to the rules of Mendelian inheritance, genetic diseases due to faulty genes located on autosomes (chromosomes other than X or Y) are equally transmitted from the parent of either sex. This is indeed the case for the vast majority of genetic diseases. Why should it matter to the offspring whether a given […]

Regulation of DNA methylation by Dnmt3L (Genetics)

The mammalian genome contains roughly 3 x 107 CpG dinucleotides, and about 60% of these are methylated at the 5-position of the cytosine. Most 5-methycytosine (m5C) is in transposable elements and their remnants, and removal of methylation by means of mutations in DNA-methyltransferase genes causes the transcriptional activation of transposons in germ and somatic cells. […]

The histone code and epigenetic inheritance (Genetics)

1. Histones and chromatin Histones constitute a family of remarkably conserved proteins that are assembled into nucleosomes that are composed of eight core proteins arrayed as four heterodimers of canonical histones (H2A:H2B, H3:H4, H3:H4, H2A:H2B) around which 147 bp of DNA is wrapped 1.7 times (Luger et al., 1997). The nucleosomes, which are connected to […]

Imprinting and epigenetics in mouse models and embryogenesis: understanding the requirement for both parental genomes (Genetics)

1. Introduction Twenty years ago, the developmental fate of uniparental embryos was described in mammals. Elegant nuclear transplantation studies in the mouse determined that both a maternal and a paternal genome are required to complete normal development (McGrath and Solter, 1984; Barton et al., 1984). Parthenogenetic and gynogenetic embryos possess only maternally derived chromosomes. The […]

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