Precise chromosomal DNA replication during S phase of the cell cycle is a crucial factor in the proper maintenance of the genome from generation to generation. The current “once-per-cell-cycle” model of eukaryotic chromosome duplication describes a highly coordinated process by which temporally regulated replicon clusters are sequentially activated and subsequently united to form two semi-conserved copies of the genome. Replicon clusters, or replication domains, are comprised of individual replication units that are synchronously activated at predetermined points during S phase. Bi-directional replication within each replicon is initiated at periodic AT-rich origins along each chromosome. Origins are not characterized by any specific nucleotide sequence, but rather the spatial arrangement of origin replication complexes (ORCs). Given the duration of the S phase and replication fork rate, adjacent origins must be appropriately spaced to ensure the complete replication of each replicon. Chromatin arrangement by the nuclear matrix may be the underpinning factor responsible for ORC positioning. The six subunit ORC binds to origins of replication in an ATP-dependent manner during late telophase and early G1. In yeast, each replication domain simply contains a single ORC binding site. However, more complex origins are characterized by an initiation zone where DNA synthesis may begin at numerous locations. A single round of DNA synthesis at each activated origin is achieved by “lic...
The fungus Sordaria fimicola is commonly used to study the different processes of cell cycles such as the assortment of genes and the crossing over during meiosis. Considering the importance of genetics in the world today, this experiment is crucially valuable in helping the students gain knowledge in the different processes of cell cycle and learning how to attempt similar experiments on their own in the future. Sordaria fimicola requires “both mitotic and meiotic nuclear divisions to manufacture eight haploid ascospores” (Helm, 1998). This fungus “spend most of its life in haploid condition” (Glase, 1995). When the haploid nuclei fuse together in the cells, they beco...
Trisomy 13 or Patau Syndrome” Trisomy 13 is a genetic disorder found in babies. It is also called Patau syndrome in honor of the physician who first described it, Krause Palau. Trisomy 13 is a genetic disorder in which there is three copies of chromosomes on Chromosome 13. Patau first described the syndrome and its involvement with trisomy in 1960. It is sometimes called Bartholin-Patau syndrome, named in part for Thomas Bartholin, a French physician who described an infant with the syndrome in 1656.
Sexual reproduction is that the union of male and feminine gametes to create a fertilised egg or zygote. The ensuing offspring inherit one-half their traits from every parent. Consequently, they 're not genetically similar to either parent or siblings, except within the case of identical twins. As theorised by Mendel, adults are diploid, meaning as 2N, having 2 alleles offered to code for one attribute. The gametes should be haploid, signified by N, containing just one allele in order that once 2 haploid gametes mix, they manufacture a traditional diploid individual. The method where haploid sex cells are created from diploid parents is known as meiosis, and it happens solely within the reproductive organs.
Mechanisms and Functions of ATP-Dependent Chromatin-Remodeling Enzymes Geeta J. Narlikar, Tom Owen-Hughes Email DOI: http://dx.doi.org/10.1016/j.cell.2013.07.011
Telomere are special DNA structure that consist of repetitive nucleotide sequences, which serves as a “cap” to protect the ends of the chromosomes. These repetitive sequences can range from thousands of base pairs in Vertebrates to about a few hundreds of base pairs in yeast cells (Oeseburg, et al. 2009). Located at the ends of the chromosomes, the telomeres serves as a biological life line for cells. Once the telomeres reach a certain length, the cell will cease to divide. Oeseburg, et al (2009) suggested that the telomere has a crucial length, once reached, it could result in chromosome end-to-end fusion and chromosome dysfunction; which may eventually lead to cell apoptosis, c...
To create a clone is to create identical copy. This imprecise definition can be tied to a number of creatures and processes in biology, those including, mono zygote (identical) twins (when one fertilized egg splits into two embryos in the first week of fertilization) , horticulture (a section of plant being implanted in a different place to create a decedent of the original plant) , and parthenogenesis (the method of asexual reproduction by females.) The creatures and processes listed above all fall under the category clones and cloning, but the difference between these and the clones and cloning processes normally referenced in, for example, science fiction, is where they occur. The examples listed are naturally occurring clones and cloning techniques, regarded as biology clones, whereas the other type of clones and cloning occurs artificially or in laborites. This genre of cloning is cloning in biotechnology. This cloning specifically refers to three established techniques: reproductive cloning, therapeutic cloning, and gene cloning. From observing the biological, naturally occurring cloning, scientists were able to create methods for created clones that are created in the laboratory intentionally. Although clones created through biotechnology are commonly associated with fantasy and science fiction, cloning animals with biotechnology is no fiction. There are even examples of animals being somewhat successfully cloned by scientists such as the lionized Dolly the Sheep. This type of technology even has the potential to clone humans, or extinct animals. Even though scientist have advanced technology and knowledge on cloning, the topic of whether or not this technology should be used is controversial. Despite the controversy and p...
DNA replication DNA replication begins with a partial unwinding of the double helix at an area known as the replication fork. This unwinding is accomplished by an enzyme known as DNA helicase. This unwound section appears under electron microscopes as a "bubble" and is thus known as a replication
DNA supercoiling occurs in all cells that undergo genetic processing. This event blocks replicative and transcriptional machinery from binding to the DNA helix, which proves detrimental to the cell. However, current research is beginning to show that not all affects of supercoiling produce negative results. These studies prove that different coiling patterns increase the efficiency of epigenetic processes such as methylation and acetylation. Topoisomerase, a post-transcriptional monomeric enzyme, solves the winding problem of the double helix by implementing transient cuts in the genome. As these cuts build up, the genome is essentially fragmented by the enzyme and the cell is unable to express essential genes; this genomic degradation by topoisomerase serves as a viable pathway into cancer research. This review article synthesizes the many ideas surrounding topological cellular events, and presents a new direction for research on chromatin modification in cancerous cells. However, due to the time constraints of the project, this article will not thoroughly discuss the mechanistic process of the replication pathway.
Mitosis July 21, 2005 Summary In the lab exercise related to Mitosis, we view various slides containing cells undergoing Mitosis. We viewed 2 different specimens: a slide of an onion root tip and a slide of Ascaris eggs. Some of the cells are at different phases of Mitosis (Interphase, Prophase, Metaphase, Anaphase, Telophase).
Past research has shown increases in the recombination rates due to environmental stressors including age, food availability, behavioral stresses, chemicals and most importantly temperature. This study looks at the effects of an increase in incubation temperature on recombination rates in Drosophila melanogaster. A wildtype parent for three genes (al+ dp+ and b+) was crossed with a recessive parent (al dp b). These genes included presence of aristala, wing type and body color, all found on the second chromosome. The parents were mated and the organisms were divided into two different vials each placed in a different temperature; one in 25°C and the other in 30°C. The offspring were counted based on their phenotype for the three studied traits. It was predicted that there would be an increase
A chromosome is made up of two identical structures called chromatids. The process of nuclear division is called interphase; each DNA molecule in a nucleus makes an identical copy of itself. Each copy is contained in the chromatid and a characteristic narrow region called the centromere holds the two chromatids together. The centromere can be found anywhere along a chromosome but the position is the characteristic for a particular chromosome. Each Chromatid contains one DNA molecule. DNA is the molecule of inheritance and is made up of a series of genes. The fact that the two DNA molecules in the sister chromatids, and hence their genes, are identical is the key to precise nuclear division.
Centrosome biogenesis is initiated in the G1 phase. The centrosome duplication cycle which is normally coordinated with the cell cycle, also faces exceptions in the case of spermatogenesis in which centrosome duplication occurs before the second meosis, and in cancer cell.
permanently in the G1 phase. Next is the S phase, in which the mass of
Meiosis is a specialized form of nuclear division in which there two successive nuclear divisions (meiosis I and II) without any chromosome replication between them. Each division can be divided into 4 phases similar to those of mitosis (pro-, meta-, ana- and telophase). Meiosis occurs during the formation of gametes in animals.
During this phase the DNA aka “deoxyribose nucleic acid” clone then forms chromatin. Chromatin is the mass of genetic material that forms into chromosomes. Interphase is divided into smaller parts: G1 Phase, S phase and G2 Phase. Throughout all the phases, the cells continuously develop by producing mitochondria, endoplasmic reticulum, and proteins. The actual division occurs during the S phase bur the G phases are mainly for the purpose of growing. Starting with the G1 phase the cell grows in preparation for certain intracellular components and DNA replication. This phase makes sure the cell is prepared for the process of DNA replication. It reviews the size and environment to ensure that is it ready to go, and cannot leave the G1 until it is complete. But what happens to a cell when it is not complete and cannot exit out of the phase? It will pause and transfer to phase G0. There’s no certain time to be in this phase but it will remain until it reaches the fitting size and is in a supportive surroundings for DNA replication. It will exit either G1 or G0 and there is no other way besides these. Then the cell will advance to the next phase which is the S phase. Synthesis, or more known as S phase is the section of the cell cycle when the DNA is wrapped into chromosomes then duplicated. This is a very important part of the cycle because it grants each of them that is created, to have the exact same genetic