1.10
Types of Genetic Transfer Between Organisms
Genetic transfer occurs when genetic information is transferred from one organism to another.
There are two types of genetic transfer: vertical and horizontal.
Vertical gene transfer, the most common of the two, is the transmission of genetic information from one generation to the next.
Vertical gene transfer occurs in sexually reproducing organisms, where they pass roughly half of the DNA onto the offspring, and in asexually reproducing organisms, which produce genetically identical progeny.
Horizontal gene transfer, conversely, occurs when genetic material from one organism is introduced to another organism of the same generation.
In the case of some prokaryotic species, such as bacteria, horizontal gene transfer can occur between different species.
Horizontal gene transfer in prokaryotes occurs via three mechanisms: transformation, transduction, and conjugation.
In transformation, a prokaryotic cell takes up naked DNA from the environment.
During transduction, viruses, bacteriophages in this example, degrade their host’s DNA. Small lengths of the host’s DNA can be packaged into the bacteriophage’s progeny before the host cell lyses.
The viral progeny then go on to infect more bacterial cells, thus becoming inadvertent mediators to transduction.
In conjugation, DNA is directly transferred from one cell to another via a structure called the sex pilus.
While conjugation is a form of ‘mating’ for asexually reproducing organisms, it is not true sexual reproduction because there are no gametes exchanged or offspring produced.
Each of these mechanisms can be observed in nature and have laboratory applications.
For example, conjugation can be used to confer antibiotic resistance from one bacterial strain to another, resulting in strains that can be resistant to multiple antibiotics.
Genetic transfer occurs when genetic information is passed from one organism to another. It occurs via two mechanisms: vertical gene transfer and horizontal gene transfer. Vertical gene transfer occurs when genetic information is transferred from one generation to the next, which happens much more frequently than horizontal gene transfer. Both sexual and asexual reproduction are forms of vertical gene transfer, where one or more organisms pass some or all of their genome onto their progeny. Additionally, vertical gene transfer occurs in both prokaryotic and eukaryotic species.
Horizontal gene transfer occurs when genetic information is passed to a member of the same generation and happens most frequently in prokaryotic species. While inter-species horizontal gene transfer is exceedingly rare among eukaryotes, it occurs frequently in prokaryotes. Horizontal gene transfer between different species is a significant source of genetic diversity among prokaryotes.
Most prokaryotic species reproduce asexually. While this allows for faster production of offspring, the offsprings produced possess limited genetic diversity. Horizontal gene transfer, therefore, serves a vital role in introducing genetic diversity to prokaryotes. Through horizontal gene transfer, prokaryotes can share a small fraction of their genome with other organisms, either conspecific (the same species) or allospecific (a different species), in the same generation. Many scientists posit that horizontal gene transfer and mutation are the most significant sources of genetic variation in prokaryotes. Thus, horizontal gene transfer provides some of the raw material upon which natural selection acts.
A prominent example of this is the emergence of antibiotic-resistant strains of bacteria. Genes that confer resistance to an antibiotic can be transferred between different species and strains of bacteria, giving the recipient bacteria a selective advantage, such as penicillin-resistant strains of Neisseria gonorrhoeae, which causes gonorrhea. On an even grander scale, some estimates suggest that at least 18% of E. coli’s genome was acquired via horizontal gene transfer over the course of millions of years of evolution.
Typen genetische overdracht tussen organismen
Genetische overdracht vindt plaats wanneer genetische informatie wordt doorgegeven van het ene organisme naar het andere. Dit gebeurt via twee hoofdmechanismen: verticale genoverdracht en horizontale genoverdracht.
Verticale genoverdracht treedt op wanneer genetische informatie wordt doorgegeven van de ene generatie op de volgende. Dit proces komt veel vaker voor dan horizontale genoverdracht. Zowel seksuele als aseksuele voortplanting zijn vormen van verticale genoverdracht, waarbij één of meerdere organismen een deel of hun volledige genoom overdragen aan hun nakomelingen. Verticale genoverdracht vindt plaats in zowel prokaryoten als eukaryoten.
Horizontale genoverdracht daarentegen treedt op wanneer genetische informatie wordt overgedragen tussen organismen binnen dezelfde generatie. Dit proces komt het vaakst voor bij prokaryoten. Hoewel inter-species horizontale genoverdracht uiterst zeldzaam is bij eukaryoten, is het een veelvoorkomend mechanisme bij prokaryoten en een belangrijke bron van genetische diversiteit binnen deze groep.
De meeste prokaryotische soorten planten zich aseksueel voort. Dit zorgt voor een snelle productie van nakomelingen, maar resulteert in een beperkte genetische diversiteit. Horizontale genoverdracht speelt daarom een cruciale rol bij het introduceren van genetische variatie in prokaryoten. Via dit proces kunnen prokaryoten een klein deel van hun genoom delen met andere organismen, zowel soortgenoten (conspecifiek) als organismen van een andere soort (allospecifiek), binnen dezelfde generatie. Veel wetenschappers beschouwen horizontale genoverdracht en mutatie als de belangrijkste bronnen van genetische variatie in prokaryoten. Deze variatie vormt de basis waarop natuurlijke selectie inwerkt.
Een bekend voorbeeld hiervan is het ontstaan van antibioticaresistente bacteriestammen. Genen die resistentie tegen antibiotica verlenen, kunnen tussen verschillende soorten en bacteriestammen worden overgedragen, waardoor de ontvangende bacteriën een selectief voordeel krijgen. Zo zijn er penicilline-resistente stammen van Neisseria gonorrhoeae, de bacterie die gonorroe veroorzaakt.
Op een grotere schaal suggereren sommige schattingen dat minstens 18% van het genoom van Escherichia coli via horizontale genoverdracht is verkregen gedurende miljoenen jaren van evolutie.
Genetic transfer occurs when genetic information is transferred from one organism to another.
There are two types of genetic transfer: vertical and horizontal.
Vertical gene transfer, the most common of the two, is the transmission of genetic information from one generation to the next.
Vertical gene transfer occurs in sexually reproducing organisms, where they pass roughly half of the DNA onto the offspring, and in asexually reproducing organisms, which produce genetically identical progeny.
Horizontal gene transfer, conversely, occurs when genetic material from one organism is introduced to another organism of the same generation.
In the case of some prokaryotic species, such as bacteria, horizontal gene transfer can occur between different species.
Horizontal gene transfer in prokaryotes occurs via three mechanisms: transformation, transduction, and conjugation.
In transformation, a prokaryotic cell takes up naked DNA from the environment.
During transduction, viruses, bacteriophages in this example, degrade their host’s DNA. Small lengths of the host’s DNA can be packaged into the bacteriophage’s progeny before the host cell lyses.
The viral progeny then go on to infect more bacterial cells, thus becoming inadvertent mediators to transduction.
In conjugation, DNA is directly transferred from one cell to another via a structure called the sex pilus.
While conjugation is a form of ‘mating’ for asexually reproducing organisms, it is not true sexual reproduction because there are no gametes exchanged or offspring produced.
Each of these mechanisms can be observed in nature and have laboratory applications.
For example, conjugation can be used to confer antibiotic resistance from one bacterial strain to another, resulting in strains that can be resistant to multiple antibiotics.
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