Introduction
The idea that genes are individual units that perform unique functions is a misconception. In fact, genes interact with each other. Epistasis is a phenomenon based on the concept of gene interaction whereby, the effect of a specific gene on the phenotype of an individual is either masked or reinforced by one or more different genes (Natural Standard, 2013). It is important to underline that epistasis involves the interaction between different genes and that the result of this interaction is related to the susceptibility to various human diseases (Nagel 2005). An example of such human disease is the Alzheimer’s Disease (AD), a severe disease causing brain degeneration, strongly affecting memory. Recently, the focus on the study of epistasis has been enhanced as it has been acknowledged that the study of gene interaction is crucial for further understanding complex diseases.
The concept of Epistasis
There are two major definitions aiming to explain the concept of epistasis: William Batesons’ definition (1909) of compositional epistasis and Ronald Fisher’s Statistical definition (1918) of statistical epistasis (Cordell 2002). Bateson’s definition describes the distortion of Mendel’s segregation ratios as a result of one gene masking the effects of another. On the other hand, Fisher viewed epistasis as the statistical deviation from the additive combinations of the position of two or more different genes on a chromosome from their effect on a quantitative phenotype (Philips 2008). Fisher’s definition is more relevant to the idea of statistical interaction as opposed to Bateson’s definition that is mostly biological. The two different definitions give rise to questioning whether biological findings ensure that statistic...
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...n H. (2005). A global view of epistasis. Nature Genetics. 37 (1), p13-14
9. Nagel,R. (2005). Epistasis And The Genetics Of Human Diseases. Comptes Rendus Biologies. 328.7 (1), p606-615.
10. Philips, Patrick C. (2008). Epistasis — the essential role of gene interactions in the structure and evolution of genetic systems. Nature Reviews Genetics . 9 (11), p855-867.
Websites
1. Natural Standard. (2013). Epistasis. Available: http://www.naturalstandard.com/databases/genomics/all/genomic-epistasis.asp. Last accessed 25th Feb 2014.
2. National Institute of Health. (2011). Alzheimer's Disease Genetics. Available: http://www.nia.nih.gov/sites/default/files/alzheimers_disease_genetics_fact_sheet_1.pdf. Last accessed 27th Feb 2014.
3. Alzheimer Disease Overview - GeneReviews™ - NCBI Bookshelf.Available: http://www.ncbi.nlm.nih.gov/books/NBK1161/. Last accessed 27 Feb 2014.
In 1990, the first great stride of genetics took place. This was called the Human Genome Project, a large-scale operation that was designed to understand the human genome (genetic structure). Since its commencement, there have been many leaps and bounds that have taken place. For certain genetic issues that we once knew nothing about, we no...
-Reilly Philip. Is It In Your Genes. Cold Spring Harbor Laboratory Press. 2004: 223-228. Print
According to Klug, &Ward (2009), members of a certain population from another are distinguished by the presence of unique genetic characteristics. It is believed that large populations have greater diversity of alleles, compared to the small populations. In most cases, the diversity of alleles designates a greater potential for any evolution of new genes combination. This also shows greater capacity for evolution in adapting different environmental condition. On the other hand, individuals in small populations are possible to be hereditarily, anatomically as well physiologically more consistently than in large populations.
Lewis, Ricki, (2014), Human Genetics, 11th Edition, Chapter 15 Changing Allele Frequencies, pp 293. [VitalSource Bookshelf Online]. Retrieved from
The exercise involved a series of ‘mating’ events resulting in 6 generations. Each mating event produced offspring with ‘possible’ newly inherited traits. The idea of ‘chance’ was included through simple coin tosses. Also, ideas of selection and mutations were introduced into the ‘gene pool’, which presented a deeper and more clear understanding of Mendelian inheritance and the Hardy-Weinberg equilibrium. Upon reaching the third generation, A B1 mutant allele was introduced to the blue locus-influencing fin shape and a G1 mutant allele was introduced to the green locus-influencing Mouth
of diagnosis is about 80 years old (Johnson, 1989). The incidence is about the same for all races, but women are more likely than men to develop the disease, because they live longer. The second factor is heredity. Family history plays a role in about forty percent of people with early onset of Alzheimer’s (Johnson, 1989). If your parents or a sibling developed the disease, you are more likely to, as well. But there are cases of families with several people who have had this disease and other members are not affected. These two factors are the only proven factors, but environmental research is being done to help with a possible protective effect for the disease. As of now, more research is needed to confirm any be...
Alzheimer’s disease is believed to be a result from a combination of genetic, lifestyle, and environmental factors that affect the brain over time. It is stated that less than five percent of the time Alzheimer's is caused by specific genetic changes that virtually guarantee a person will develop the disease. It is not yet fully understood the actual causes of Alzheimer’s disease.
In this experiment, Mendelain Models are observed. The purpose of the experiment is to understand how traits are passed from one generation to the other as well as understanding the difference between sex linked and autosomal genes. One particular trait that is observed in this experiment is when a fly is lacking wings, also known as an apterous mutation. In this experiment, we will determine whether this mutation is carried on an autosomal chromosome or on a sex chromosome. The data for this experiment will be determined statistically with the aid of a chi-square. If the trait is autosomal, then it will be able to be passed to the next generation on an autosomal chromosome, meaning that there should be an equal amount of male and
Secko, David. “Alzheimer’s Disease: Genetic Variables and Risk.” Canadian Medical Association Journal. March 2005: 172-5.
Epigenetics is the study of both heritable and non-heritable changes in gene translation, which do not stem from mutation. Epigenetic alterations to DNA may occur in several different ways; histone modification, DNA methylations, expression of microRNAs, and changes of the chromatin structure (Ntanasis-Stathopoulos et al). Depending on their presentation, they may be passed on to offspring. The exact mechanism of heritable epigenetic modification has not been discovered, but all of these alterations may have some impact on a wide range of disorders and have far reaching implications in the medical field. The study of epigenetics seeks to answer the age old question of whether nature or nurture is responsible for our phenotype, and it has arrived at the answer that in fact, both are. The discovery of epigenetic changes may lead us to cure many disorders, and even personality problems.
...le promiscuity." Nature Genetics 36.12 (2004): 1326-1329. Academic Search Complete. EBSCO. Web. 24 July 2011.
...ses of linkage and to observe that the four different phenotypes produced by a dihybrid cross as aforementioned must occur in an 9:3:3:1 ratio. Correns also implied that segregation was a result of meiosis (Moore, 2001).
Alzheimer’s Disease is named after a German doctor, who specializes in the brain and nervous system, named Alois Alzheimer. This Disease forms in the brain. Alzheimer’s is the most common form of Dementia, a general term for memory loss and other intellectual abilities serious enough to enter. The Tau protein ensures the tubes in your brain stay straight allowing molecules to pass through freely. In Alzheimer’s Disease the protein collapses into strands or tangles, making the tubes disintegrate. There is visible differences of brain tissue in the from misfolded proteins called plaques and tangles. Beta-Amyloid clumps block signals and communication between cells in the brain. Researchers agree that Alzheimer’s Disease is m...
Alzheimer's is a very complex disease. So complex that very little has been discovered about it but that is rapidly changing. Findings from epidemiology, genetics, molecular and cell biology are fitting together in the Alzheimer's puzzle, helping researchers to identify some of the mechanisms that underlie it. Alzheimer's starts because the normal processing of certain proteins goes terribly wrong. This causes brain cells and the spaces between them to be cluttered with pieces of toxic protein. Closer investigating with microscopes has revealed a loss of nerve cells in certain regions of the brain. Some of these dying nerve cells communicate using the neurotransmitter acetylcholine, these compounds eventually break down by an enzyme called acetylcholinesterase. Also responsible for Alzheimer's are clusters of proteins in the brain which come in two forms: those found inside the nerve cells and those found in between the cells.
...ary part in genotypes of potential interest that human geneticists breeders, as well as evolutionary geneticists are investigating. However, although we have the capability to unravel experiments that the founders of quantitative genetics would have never imagined, but their basic, un-computational machinery that they developed is most easily adaptable to the latest analyses that will be needed. We are far from ‘letting-go’ molecular biologists from the mathematical techniques/systems, because this age in respect to genomics has been forced into accepting gratitude due to the major importance of quantitative methods as opposed to the new molecular genetics. As geneticists tend to map molecular variation as well as genomic data, quantitative genetics will be moving to the front position because of its relevance in this age of rapid advancement in molecular genetics.