Which one of the following statements best describes the purpose of Si...
Explanation:
Site Directed Nuclease (SDN)
Definition:
Site Directed Nuclease (SDN) refers to the DNA cutting enzymes used for the generation of targeted DNA breaks.
Purpose:
The primary purpose of SDN is to introduce targeted DNA breaks at specific locations within the genome. This technology allows for precise modifications to be made to the genetic material, such as gene editing or gene knockout.
Function:
SDN works by utilizing engineered nucleases, such as CRISPR-Cas9, to create double-strand breaks at desired sites in the DNA. These breaks can then be repaired by the cell's own repair machinery, leading to the introduction of specific genetic changes.
Applications:
- SDN has a wide range of applications in various fields, including biotechnology, agriculture, and medicine.
- In agriculture, SDN can be used to develop crops with improved traits, such as disease resistance or increased yield.
- In medicine, SDN holds promise for the treatment of genetic disorders by correcting disease-causing mutations in the genome.
Advantages:
- SDN offers a more precise and efficient method of genome editing compared to traditional methods.
- It allows for the modification of specific genes without affecting the rest of the genome.
Conclusion:
In conclusion, Site Directed Nuclease (SDN) plays a crucial role in enabling targeted genetic modifications with high precision and efficiency. This technology has the potential to revolutionize various fields by facilitating the development of novel therapies, improved crops, and other applications.
Which one of the following statements best describes the purpose of Si...
- SDN or sequence specific nuclease (SSN) refers to the practice of cleaving DNA strands to affect the subsequent genome editing. SDN technology takes advantage of targeted DNA break and host’s natural repair mechanisms to introduce specific small changes at the site of the DNA break.
- The basis of current targeted genome editing applications is the capacity to induce a DNA double strand break (DSB) at a selected location in the genome where the modification is intended. Directed repair of the DSB allows for targeted genome editing. Such applications can be applied to generate mutations (targeted mutations or precise native gene editing) as well as precise insertion of genes (cisgenes, intragenes, or transgenes).
- Different approaches can be used to achieve targeted DNA breaks, including Meganucleases (MN), Zinc Finger Nucleases (ZFNs), Transcription Activator-Like Effector Nucleases (TALENs) and the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-associated proteins (CRISPR/Cas) etc. Collectively, these are often discussed under the acronym site directed nucleases (SDNs), pointing out to the general principle of the technology to use a DNA cutting enzyme (nuclease) for the generation of the targeted (or site directed) DNA break. Hence option (b) is the correct answer.
- Variants of SDN applications are often categorized as SDN-1, SDN-2 and SDN-3 depending on the outcome of the DNA double strand break repair.
- SDN-1: When the SDN is used in the absence of a DNA repair template (see SDN-2/-3), the outcome is a targeted, non-specific genetic deletion mutation. In this case, the position of the DNA DSB is precisely selected, but the DNA repair by the host cell is random and results in small nucleotide deletions, additions or substitutions.
- SDN-2: Is used to generate gene editing mutations. In this case, a SDN is used to generate a targeted DSB and a DNA repair template (a short DNA sequence identical to the targeted DSB DNA sequence except for one or a few nucleotide changes) is used to repair the DSB. The outcome is a targeted and predetermined point mutation in the desired gene of interest.
- SDN-3: When the SDN is used along with a DNA repair template that contains new DNA sequence (e.g.gene), the outcome of the technology would be the integration of that DNA sequence into the plant genome. The most likely application illustrating the use of SDN-3 would be the insertion of cisgenic, intragenic, or transgenic expression cassettes at a selected genome location.
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