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Genetics is the study of genes, genetic variation, and heredity in organisms. It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinian friar working in the 19th century in Brno, was the first to study genetics scientifically. Mendel studied "trait inheritance", patterns in the way traits are handed down from parents to offspring over time. He observed that organisms inherit traits by way of discrete "units of inheritance". This term, still used today, is a somewhat ambiguous definition of what is referred to as a gene.
Microevolution is the change in allele frequencies that occurs over time within a population. This change is due to four different processes: mutation, selection, gene flow and genetic drift. This change happens over a relatively short amount of time compared to the changes termed macroevolution.
Lactose intolerance is caused by a lessened ability or a complete inability to digest lactose, a sugar found in dairy products. Humans vary in the amount of lactose they can tolerate before symptoms develop. Symptoms may include abdominal pain, bloating, diarrhea, flatulence, and nausea. These symptoms typically start thirty minutes to two hours after eating or drinking something containing lactose, with the severity typically depending on the amount consumed. Lactose intolerance does not cause damage to the gastrointestinal tract.
Genetic drift, also known as random genetic drift, allelic drift or the Wright effect, is the change in the frequency of an existing gene variant (allele) in a population due to random chance.
Horizontal gene transfer (HGT) or lateral gene transfer (LGT) is the movement of genetic material between organisms other than by the ("vertical") transmission of DNA from parent to offspring (reproduction). HGT is an important factor in the evolution of many organisms. HGT is influencing scientific understanding of higher order evolution while more significantly shifting perspectives on bacterial evolution.
Population genetics is a subfield of genetics that deals with genetic differences within and among populations, and is a part of evolutionary biology. Studies in this branch of biology examine such phenomena as adaptation, speciation, and population structure.
In population genetics, gene flow is the transfer of genetic material from one population to another. If the rate of gene flow is high enough, then two populations will have equivalent allele frequencies and therefore can be considered a single effective population. It has been shown that it takes only "one migrant per generation" to prevent populations from diverging due to drift. Populations can diverge due to selection even when they are exchanging alleles, if the selection pressure is strong enough. Gene flow is an important mechanism for transferring genetic diversity among populations. Migrants change the distribution of genetic diversity among populations, by modifying allele frequencies. High rates of gene flow can reduce the genetic differentiation between the two groups, increasing homogeneity. For this reason, gene flow has been thought to constrain speciation and prevent range expansion by combining the gene pools of the groups, thus preventing the development of differences in genetic variation that would have led to differentiation and adaptation. In some cases dispersal resulting in gene flow may also result in the addition of novel genetic variants under positive selection to the gene pool of a species or population
In evolutionary genetics, Muller's ratchet is a process which, in the absence of recombination, results in an accumulation of irreversible deleterious mutations. This happens because in the absence of recombination, and assuming reverse mutations are rare, offspring bear at least as much mutational load as their parents. Muller proposed this mechanism as one reason why sexual reproduction may be favored over asexual reproduction, as sexual organisms benefit from recombination and consequent elimination of deleterious mutations. The negative effect of accumulating irreversible deleterious mutations may not be prevalent in organisms which, while they reproduce asexually, also undergo other forms of recombination. This effect has also been observed in those regions of the genomes of sexual organisms that do not undergo recombination.
Genetic diversity is the total number of genetic characteristics in the genetic makeup of a species, it ranges widely from the number of species to differences within species and can be attributed to the span of survival for a species. It is distinguished from genetic variability, which describes the tendency of genetic characteristics to vary.
In biology, polymorphism is the occurrence of two or more clearly different morphs or forms, also referred to as alternative phenotypes, in the population of a species. To be classified as such, morphs must occupy the same habitat at the same time and belong to a panmictic population.
This is a list of topics in evolutionary biology.
Lactase persistence is the continued activity of the lactase enzyme in adulthood, allowing the digestion of lactose in milk. In most mammals, the activity of the enzyme is dramatically reduced after weaning. In some human populations though, lactase persistence has recently evolved as an adaptation to the consumption of nonhuman milk and dairy products beyond infancy. Lactase persistence is very high among northern Europeans, especially Irish people. Worldwide, most people are lactase non-persistent, and are affected by varying degrees of lactose intolerance as adults. However, lactase persistence and lactose intolerance do not always overlap.
Human genetic variation is the genetic differences in and among populations. There may be multiple variants of any given gene in the human population (alleles), a situation called polymorphism.
Microbial genetics is a subject area within microbiology and genetic engineering. Microbial genetics studies microorganisms for different purposes. The microorganisms that are observed are bacteria, and archaea. Some fungi and protozoa are also subjects used to study in this field. The studies of microorganisms involve studies of genotype and expression system. Genotypes are the inherited compositions of an organism. Genetic Engineering is a field of work and study within microbial genetics. The usage of recombinant DNA technology is a process of this work. The process involves creating recombinant DNA molecules through manipulating a DNA sequence. That DNA created is then in contact with a host organism. Cloning is also an example of genetic engineering.
The following outline is provided as an overview of and topical guide to genetics:
Arsenite methyltransferase is an enzyme that in humans is encoded by the AS3MT gene.
Host–parasite coevolution is a special case of coevolution, where a host and a parasite continually adapt to each other. This can create an evolutionary arms race between them. A more benign possibility is of an evolutionary trade-off between transmission and virulence in the parasite, as if it kills its host too quickly, the parasite will not be able to reproduce either. Another theory, the Red Queen hypothesis, proposes that since both host and parasite have to keep on evolving to keep up with each other, and since sexual reproduction continually creates new combinations of genes, parasitism favours sexual reproduction in the host.
Genetic ecology is the study of the stability and expression of varying genetic material within abiotic mediums. Typically, genetic data is not thought of outside of any organism save for criminal forensics. However, genetic material has the ability to be taken up by various organisms that exist within an abiotic medium through natural transformations that may occur. Thus, this field of study focuses on interaction, exchange, and expression of genetic material that may not be shared by species had they not been in the same environment.
N-6 adenine-specific DNA methyltransferase 1 is a protein that in humans is encoded by the N6AMT1 gene.
Sarah Anne Tishkoff is an American geneticist and the David and Lyn Silfen Professor in the Department of Genetics and Biology at the University of Pennsylvania. She also serves as a director for the American Society of Human Genetics and is an associate editor at PLOS Genetics, G3, and Genome Research. She is also a member of the scientific advisory board at the David and Lucile Packard Foundation.
References
- ↑ Karin Broberg. Karolinska Institute
- ↑ Professorsinstallation. Lund University. Retrieved 10 May 2022.
- ↑ Schläwicke Engström K, Broberg K, Concha G, Nermell B, Warholm M, Vahter M (2007) "Genetic polymorphisms influencing arsenic metabolism: evidence from Argentina." Environmental Health Perspectives115:599-605.
- ↑ Engström K, Vahter M, Mlakar SJ, Concha G, Nermell B, Raqib R, Cardozo A, Broberg K (2011) "Polymorphisms in arsenic(+III oxidation state) methyltransferase (AS3MT) predict gene expression of AS3MT as well as arsenic metabolism." Environ Health Perspect119:182-8.
- ↑ Schlebusch CM, Gattepaille LM, Engström K, Vahter M, Jakobsson M, Broberg K (2015) "Human adaptation to arsenic-rich environments." Molecular Biology and Evolution32:1544-55.
- ↑ Carl Zimmer (March 12, 2015) New York Times: "An Unlikely Driver of Evolution: Arsenic."
- ↑ Tishkoff SA, Reed FA, Ranciaro A, Voight BF, Babbitt CC, Silverman JS, Powell K, Mortensen HM, Hirbo JB, Osman M, Ibrahim M, Omar SA, Lema G, Nyambo TB, Ghori J, Bumpstead S, Pritchard JK, Wray GA, Deloukas P (2007) "Convergent adaptation of human lactase persistence in Africa and Europe". Nature Genetetics39:31-40.
- ↑ Creanza N, Feldman MW. (2016) "Worldwide genetic and cultural change in human evolution." Curr Opin Genet Dev41:85-92.
- ↑ Fan S, Hansen ME, Lo Y, Tishkoff SA. (2016) "Going global by adapting local: A review of recent human adaptation." Science354:54-59
- ↑ Palmgren M, Engström K, Hallström BM, Wahlberg K, Søndergaard DA, Säll T, Vahter M, Broberg K (2017) "AS3MT-mediated tolerance to arsenic evolved by multiple independent horizontal gene transfers from bacteria to eukaryotes." PLoS One12:e0175422.
- ↑ Dunning Hotopp JC (2011) "Horizontal gene transfer between bacteria and animals." Trends in Genetics27:157-63.
