Introduction to Cells, DNA, and Viruses
Patricia G. Melloy in Viruses and Society, 2023
One of the biggest functions of the cell is to produce proteins to do particular jobs for cells and the body as a whole. Because humans contain so many kinds of cells, we have separation of function for different groups of cells, which are organized into tissues, organs, and organ systems. Cells duplicate themselves when they are actively dividing. Cells go through a series of steps known as the cell cycle, in which the cell prepares for DNA synthesis, then copies its DNA, then separates the DNA in the form of the chromosomes moving to opposite sides of the cell (see Figure 1.1). The cell then completes nuclear division followed by separation of the cytoplasmic contents, resulting in two cells. This process is known as mitosis. Not all cells are actively dividing, but cell division is critical during development as well as to replenish worn-out tissues in an adult organism. When cells do a particular job for the body, they need to create proteins encoded in the DNA. Cells come in many shapes and sizes, but what they all have in common is the procedure needed to convert the hereditary material to functional protein in the body.
Basic Cell Biology
Kedar N. Prasad in Handbook of RADIOBIOLOGY, 2020
This kind of nuclear division occurs only in the germinal cells (ovary and testis). In the testis during meiosis, each member of a paired chromosome duplicates, and the duplicated members come to lie side by side in a four-stranded configuration. The successive nuclear divisions result in the formation of four sperm, each with a haploid set of chromosomes (half of the parent cell). During meiosis, the first nuclear division is a mitotic one in which each daughter cell receives an identical set of diploid chromosomes. The second nuclear division is a reduction division in which each daughter cell contains only the haploid set of chromosomes. Diagrammatic representations of meiosis in the testis and ovary are shown in Figures 2.3 and 2.4. In the testis, spermatogonia divide by mitosis to form primary spermatocytes, which undergo reduction division to form spermatids. Spermatids have a haploid set of chromosomes. The spermatids undergo a maturation process to form spermatozoa. The entire process of the formation of spermatoza is called spermatogenesis. The basic process of meiosis in the female is the same, except that each oocyte gives rise to only one functional egg, whereas each spermatocyte produces four functional spermatozoa. The process of forming the functional egg is called oogenesis.
Genetic influences on antisocial behaviour, problem substance use and schizophrenia: evidence from quantitative genetic and molecular genetic studies
John C. Gunn, Pamela J. Taylor in Forensic Psychiatry, 2014
There are two kinds of cell division: mitosis and meiosis. Mitosis is the most common form, in which a parent cell duplicates its complete genetic material (DNA replication) before cell division, resulting in daughter cells that are genetically identical. Meiosis is a form of cell division that produces sperm and egg cells. It involves two successive cell divisions, but only one round of DNA replication. Detailed description of meiotic cell division is beyond the scope of this chapter, but there are features of meiosis which are crucial to studies of genetic inheritance. First, in a process known as ‘crossing over’, there is physical breakage of the double helix followed by recombination, which results in exchange of segments of DNA between homologous chromosomes. Following this, at the first meiotic cell division, each pair of homologous chromosomes separate and assort themselves independently so that each daughter cell contains random combinations of each maternally and paternally derived set. Finally, a second meiotic division yields four daughter gametes, which are said to be haploid as they only have one representative of each chromosome pair. The full genetic complement is restored at fertilization, with the union of sperm and egg. The coupling of independent assortment and recombination ensures that the number of genetically different gametes that can be produced by a single individual is almost unlimited, resulting in considerable genetic variation between individuals, even family members.
Quantitative relationships between acentric fragments and micronuclei: new models and implications for curve fitting
Published in International Journal of Radiation Biology, 2020
For a decade (mid 70s to mid 80s), several authors investigated the quantitative relationship between AFs and MNi. Carrano and Heddle (1973) studied the kinetics of the changes in the frequencies of AFs (as well as other aberrations) during successive mitoses following irradiation. In this way, they concluded that the ratio at which an AF is inherited into a daughter cell is 0.80. Other authors (Pincu et al. 1984; Cornforth and Goodwin 1991) studied the relationship between AFs and MNi, until a new methodology was developed: the cytokinesis-blocked MN test (CBMN, Fenech and Morley 1985). This protocol exploits the property of cytochalasin-B to block only cytokinesis (division of daughter cells) without impeding mitosis. In this way, a replicating cell forms a binucleated cell after one nuclear division. This new protocol greatly improved the sensitivity of the test. In fact, as formation of a MN needs that the cell undergoes a mitosis, the yield of MNi is underestimated if non-replicating cells are counted. In the CBMN, the MNi frequency is calculated by scoring only binucleated cells, i.e. the replicating ones. Although the main aim of this new protocol was (and still is) the increase of its sensitivity, it also simplified the studies looking for the relationship between AFs and MNi.
Radiosensitivity of seedling traits to varying gamma doses, optimum dose determination and variation in determined doses due to different time of sowings after irradiation and methods of irradiation in faba bean genotypes
Published in International Journal of Radiation Biology, 2023
Rajdeep Guha Mallick, Subhradeep Pramanik, Manas Kumar Pandit, Akhilesh Kumar Gupta, Subhrajit Roy, Sanjay Jambhulkar, Ashutosh Sarker, Rajib Nath, Somnath Bhattacharyya
Siahpoosh et al. (2020) observed an increased amount of mitotic and meiotic anomalies with increasing doses of gamma radiation in mutant plants of Vicia faba cv. Saraziri. The increased amount of mutations with the increasing doses of ionizing radiation interferes with the cell division process viz., mitosis and meiosis. Mitotic anomalies result in impaired cell divisions thus halting the cell cycle at checkpoints resulting in growth retardation of meristematic cells. Differential mutation loads in plant propagules exposed to varying doses of ionizing radiation results in deviation in the growth and development of plants in comparison to the un-irradiated propagules. Meristematic cell deaths are often encountered as plants avoid the transmission of lethal mutations in advanced generations (Raina et al. 2021).
Autophagy in male reproduction
Published in Systems Biology in Reproductive Medicine, 2019
Yinci Zhu, Qingqing Yin, Dandan Wei, Zhenyu Yang, Yanzhi Du, Yi Ma
Spermatogenesis is a complex process in which successive cellular events occur sequentially in specific regions of the testis. It includes the mitosis of the spermatogonia, two meiotic divisions of the spermatocytes, spermiogenesis and spermiation. During this process, the germ cells are transported across the seminiferous epithelium by the Sertoli cells (Qian et al. 2014). The seminiferous epithelium exhibits tight junctions, gap junctions and the testis-unique junctions such as the ectoplasmic specialization (ES). ES, an actin microfilament-rich anchoring junction, includes the basal ES and apical ES. The basal ES is the constructive part of the blood-testis barrier (BTB), while the apical ES facilitates the development and maturation of the spermatid (Liu et al. 2016). After the specific knockout of Atg5 or Atg7 in the mouse Sertoli cells, the apical and basal ES were disrupted, and the cytoskeleton structure was disorganized, resulting in sperm with malformed heads and low motility. Further research revealed that a negative cytoskeleton organization regulator, PDZ and LIM domain 1 (PDLIM1), was degraded by autophagy; therefore, the deficiency of autophagy led to an abnormal accumulation of PDLIM1 and then the disorder of the cytoskeleton structure and ES assembly (Liu et al. 2016).
Related Knowledge Centers
- Cell Division
- Cytoplasm
- DNA Replication
- Interphase
- S Phase
- Telophase
- Cell Nucleus
- Cytokinesis
- Cell Cycle
- Chromosome