Cell structure, function and adaptation
C. Simon Herrington in Muir's Textbook of Pathology, 2020
Mitosis results in daughter cells being produced, each containing the full complement of DNA (46 chromosomes, diploid) (Figure 2.4), whereas in meiosis the DNA content of a cell is halved, and cells become haploid (Figure 2.5). Diploidy is achieved when two haploid cells combine, usually an egg (ovum) and a sperm. Although disturbance in the cell cycle is widely recognized to be important in the pathogenesis of cancer, an understanding of how cell proliferation is controlled is also needed to fully appreciate processes such as wound healing (see Chapter 3) and atherosclerosis (see Chapter 7). Classically, the cycle is divided into four states: gap 1 (G1), synthesis (S), gap 2 (G2), and mitosis (M), with an additional fifth state, gap 0 (G0), which is a non-cycling, resting state (Figure 2.6).
Regulation of Reproduction by Dopamine
Nira Ben-Jonathan in Dopamine, 2020
Spermatogenesis can be divided into three phases: (1) mitosis, or regular cell division; (2) meiosis, or reductional division; and (3) spermiogenesis, or cell differentiation. During the first phase, the diploid (2n) spermatogonia divide by mitosis. Primary spermatocytes then enter meiosis, a specialized cell division that is unique to male and female gametes. Meiosis differs from mitosis by three criteria. One is the halving of the number of chromosomes, so that each daughter cell is haploid (n), with only 23 chromosomes. This ensures reconstitution of the diploid status upon unification with a gamete of the opposite sex. The second involves an exchange of genetic material between homologous chromosomes during crossing over. The third is a random segregation of paternal and maternal chromosomes between the daughter cells. Hence, the number of genetically distinct gametes that can be produced by an individual is almost unlimited.
Candida Biofilms
Chaminda Jayampath Seneviratne in Microbial Biofilms, 2017
In eukaryotes, the term ‘ploidy’ refers to the number of sets of chromosomes in a biological cell [86]. Cells containing two sets of chromosomes in their genome are called diploid cells whereas those with only one set of chromosomes are called haploid cells. In the eukaryotic model organism, the budding yeast Saccharomyces cerevisiae, haploid and diploid cells are the two forms that can survive and proliferate [87]. The haploid form is the sexual form of S. cerevisiae, and haploid cells undergo a simple life cycle of mitosis and proliferation. Haploid cells of the opposite mating types can mate and generate diploid cells. S. cerevisiae haploids have a lower tolerance to unfavourable environments and tend to die under stress conditions. In contrast, the diploid cells are the asexual form of S. cerevisiae. Under certain stress conditions, diploid cells undergo sporulation, producing four haploid spores via meiosis [86].
Detection of Parental Contribution to Molar Genome Leads to Diagnosis of Recurrent Hydatidiform Mole in a Family with NLRP7 Variants
Published in Fetal and Pediatric Pathology, 2022
Rong-Yue Wang, Yu-Juan Li, Li Zhen, Fan Jiang, Cong-Min Gu, Dong-Zhi Li
Hydatidiform mole (HM) is a complication of pregnancy characterized by varying degrees of trophoblastic proliferation and vesicular swelling of placental villi, while the embryonic development is severely abnormal or absent. The diagnosis is usually made only after histopathological examination of uterine curettage specimens, which allows the classification of moles as complete HM (CHM) or partial HM (PHM) based on the degree of trophoblast proliferation and the presence or absence of fetal tissues [1]. CHM and PHM are genetically different in that CHM is androgenetic diploid, containing two sets of paternal chromosomes, while PHM is triploid with one maternal and two different paternal sets of chromosomes [2]. Occasional diploid CHMs have both maternal and paternal genomes. This type of biparental CHM (BiCHM) has clinical implication as it has been associated with recurrent HM (RHM) [3]. In this study, we report a RHM which was identified by the detection of BiCHM.
Practical applications of DNA genotyping in diagnostic pathology
Published in Expert Review of Molecular Diagnostics, 2019
As outlined in the remaining panels in Figure 4, other genotypic possibilities can exist for PHM, such as monospermic 69XXY. An example of this is shown in Figure 4(d), where one can clearly see the molar tissue (bottom panel) contains one or two alleles at many loci, with a consistent approximate 2:1 peak height ratio when two alleles are present. While some loci demonstrate a single triple-height peak such as FGA and Amelogenin, none of the loci demonstrates three peaks. The sex-determining Amelogenin locus demonstrates just one peak, the X allele. This represents a triploid genotype consisting of just two allelic variants; a monospermic partial mole with a 69XXX genotype with a diploid homozygous paternal (duplicated single sperm) and haploid maternal genomic complement, respectively.
Thiol/Disulfide Homeostasis in Patients with Molar Pregnancies
Published in Fetal and Pediatric Pathology, 2020
Meryem Kuru Pekcan, Aytekin Tokmak, Nazli Topfedaisi Ozkan, Gulnur Ozaksit, Arzu Kosem, Ozcan Erel, Mutlu Meydanli
PHM and CHM are identified through histopathologic examination of molar tissue, presence or absence of fetal or embryonic tissue, as well as genetic studies. It is well known that all chromosomes in CHM are diploid (46 XX/46 XY) and paternal in origin. Similarly, in PHM, the extra sets of chromosomes are generally paternal in origin and triploidy is present (69XXY/69XYY/69XXX) [2]. Although the genetic basis of the disease is well known, there may be also environmental factors that disturb the oocyte and/or sperm structurally or functionally, such as OS. Perhaps the imbalance between the oxidant/antioxidant defense systems during the pre-pregnancy period may potentiate the development of molar pregnancies by disrupting the physiologic mechanisms that occur during the fertilization and post-fertilization periods.
Related Knowledge Centers
- Allele
- Sexual Reproduction
- Somatic Cell
- Tissue
- Autosome
- Chromosome
- Cell
- Pseudoautosomal Region
- Gene
- Polyploidy