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Fuzzy-Genetic Approach to Epidemiology
Published in Jyoti Mishra, Ritu Agarwal, Abdon Atangana, Mathematical Modeling and Soft Computing in Epidemiology, 2020
Minakshi Biswas Hathiwala, Jignesh Pravin Chauhan, Gautam Suresh Hathiwala
The genetic data of living organisms is reserved in deoxy ribonucleic acid abbreviated as DNA. Each DNA molecule is packed in a thick-like structure called chromosome. The chromosomes differ in length from 105 base pairs in yeast to 108 base pairs in human [4]. A chromosome comprises gene blocks of DNA. Each protein is encoded by a gene. Alleles are different versions of the same gene. The whole collection of genetic material, i.e., all chromosomes, is known as a genome. In living organisms, a genome usually consists of homologous chromosomes. One of each homologous pair of chromosomes originates from the mother, while the other originates from the father.
Genes and genomics
Published in Firdos Alam Khan, Biotechnology Fundamentals, 2018
Meiosis is essential for sexual reproduction and therefore occurs in all eukaryotes (including single-celled organisms) that reproduce sexually. A few eukaryotes, notably the Bdelloid rotifers, have lost the ability to carry out meiosis and have acquired the ability to reproduce by parthenogenesis. Meiosis does not occur in archaea or bacteria, which reproduce via asexual processes such as binary fission. During meiosis, the genome of a diploid germ cell, which is composed of long segments of DNA packaged into chromosomes, undergoes DNA replication followed by two rounds of division, resulting in four haploid cells. Each of these cells contains one complete set of chromosomes or half of the genetic content of the original cell. If meiosis produces gametes, these cells must fuse during fertilization to create a new diploid cell or zygote before any new growth can occur. Thus, the division mechanism of meiosis is a reciprocal process to the joining of two genomes that occurs at fertilization. Because the chromosomes of each parent undergo genetic recombination during meiosis, each gamete, and thus each zygote, will have a unique genetic blueprint encoded in its DNA. Together, meiosis and fertilization constitute sexuality in the eukaryotes and generate genetically distinct individuals in populations. In all plants and in many protists, meiosis results in the formation of haploid cells that can divide vegetatively without undergoing fertilization, referred to as spores. In these groups, gametes are produced by mitosis. Meiosis uses many of the same biochemical mechanisms employed during mitosis to accomplish the redistribution of chromosomes. There are several features unique to meiosis, most importantly the pairing and genetic recombination between homologous chromosomes (Figure 2.10).
Genes and Genomics
Published in Firdos Alam Khan, Biotechnology Fundamentals, 2020
Meiosis is essential for sexual reproduction and therefore occurs in all eukaryotes (including single-celled organisms) that reproduce sexually. A few eukaryotes, notably the Bdelloid rotifers, have lost the ability to carry out meiosis and have acquired the ability to reproduce by parthenogenesis. Meiosis does not occur in archaea or bacteria, which reproduce via asexual processes such as binary fission. During meiosis the genome of a diploid germ cell, which is composed of long segments of DNA packaged into chromosomes, undergoes DNA replication followed by two rounds of division, resulting in four haploid cells. Each of these cells contains one complete set of chromosomes, or half of the genetic content of the original cell. If meiosis produces gametes, these cells must fuse during fertilization to create a new diploid cell, or zygote, before any new growth can occur. Thus, the division mechanism of meiosis is a reciprocal process to the joining of two genomes that occurs at fertilization. Because the chromosomes of each parent undergo genetic recombination during meiosis, each gamete, and thus each zygote, will have a unique genetic blueprint encoded in its DNA. Together, meiosis and fertilization constitute sexuality in the eukaryotes, and generate genetically distinct individuals in populations. In all plants, and in many protists, meiosis results in the formation of haploid cells that can divide vegetatively without undergoing fertilization, referred to as spores. In these groups, gametes are produced by mitosis. Meiosis uses many of the same biochemical mechanisms employed during mitosis to accomplish the redistribution of chromosomes. There are several features unique to meiosis, most importantly the pairing and genetic recombination between homologous chromosomes (Figure 2.10).
Agricultural production: assessment of the potential use of Cas9-mediated gene drive systems for agricultural pest control
Published in Journal of Responsible Innovation, 2018
Maxwell J. Scott, Fred Gould, Marcé Lorenzen, Nathaniel Grubbs, Owain Edwards, David O’Brochta
Historically, Hemiptera have not been the focus of efforts to develop genetics-based population control programs like SIT. There are some species, such as B. tabaci, that might be amenable to gene drive-based control or eradication strategies for a number of reasons. First, B. tabaci is easy to rear and has life history characteristics that make the development and introduction of various genetic technologies highly feasible in the laboratory (David O’Brochta, unpublished results). B. tabaci is highly fecund with a short life cycle of about three weeks under appropriate temperature conditions. Its eggs are about 150–200 microns in length, are easily collected, and have a very thin, translucent chorion (outer membrane) that is easily penetrated by the glass needles used to inject genetic technologies (nucleic acids and/or proteins) into developing embryos (Crisione, O’Brochta, and Reid 2015). B. tabaci has a long, slow embryonic development requiring approximately nine days to complete. Blastoderm formation, the cutoff for effective injection of most genetic technologies, occurs between the sixth and ninth hours of development (David O’Brochta, unpublished results). This extended embryonic development is convenient for developing embryo microinjection protocols for preblastoderm embryos and performing the various manipulations needed to introduce gene drive or other genetic technologies into the germ-line of insects. Preblastoderm embryo microinjection is currently the only method for introducing genetic technologies into the germ-line of insects. B. tabaci have haplo/diploid sex determination, with haploid males developing from unfertilized eggs and females developing from fertilized eggs, making them excellent subjects for genetic studies. Haploidy simplifies a number of genetic analyses and procedures, such as mutant screens and the assembly of complex genotypes involving linked and unlinked loci, among other things. One consequence of haploidy is that Cas9-mediated gene drive would only occur in heterozygous females as the drive mechanism involves copying the Cas9 gene casette to the homologous chromosome (Esvelt et al. 2014), which cannot occur in haploids.