Researchers use KO cell lines to investigate gene functions by observing the effects of gene deletion on cellular behavior. This helps in understanding the role of genes in various processes like cell growth, metabolism, and signal transduction. KO cell lines are vital for studying diseases like cancer, genetic disorders, and neurodegenerative diseases.

Not all genes are suitable for knockout. Some gene knockouts may result in cell death or severe dysfunction, particularly for essential genes. In such cases, conditional knockouts or gene knockdowns (e.g., RNAi) may be used instead.

The main difference lies in the duration and stability of gene expression: Transient cell line – The target gene is expressed temporarily in cells, typically lasting hours to days, and is suitable for short-term experiments. Stable cell line – The target gene is stably integrated into the cell genome, allowing long-term expression, suitable for extended research and production.

1.Design an efficient crRNA sequence. Proper design and structure prediction using online resources can help select suitable crRNA to achieve good trans-cleavage activity of the Cas enzyme.
2.Choose an appropriate signal reporter substrate. Research indicates that using a 15 nt single-stranded DNA (ssDNA) as a reporter substrate maximizes the cleavage reaction rate of Cas12a, significantly enhancing the reaction rate compared to the commonly used 5-nt ssDNA.
3.Optimize reaction conditions and buffers. Adjusting the CRISPR reaction parameters, such as the ratio of Cas enzyme to crRNA, the concentration of the Cas enzyme, and the reaction temperature, can improve detection performance to some extent.

When selecting a vector, consider the purpose of the experiment and the type of host cells. For example, plasmid vectors are commonly used for gene expression or amplification in bacteria, while viral vectors are more suitable for gene transfer in mammalian cells. Additionally, the vector's promoter, replicon, and antibiotic selection markers should be chosen based on specific requirements.

Induced pluripotent stem cells (iPSCs) are a type of cell that reprogram the somatic cells into a pluripotent state. They have characteristics similar to embryonic stem cells and can differentiate into almost all cell types in the body. Therefore, scientists can use IPSC cells to generate various cell types in vitro for research and treatment, instead of using embryonic stem cells to achieve the experimental purposes.

What is the difference between a single-plasmid system and a dual-plasmid system for library vectors? A single-plasmid system can achieve gene editing with one transfection, making construction relatively simple, but the larger plasmid size can lead to lower infection efficiency. In a dual-plasmid system, two vectors are used, each carrying either the Cas9 or sgRNA expression cassette. A stable Cas9 cell line is first constructed, and then the sgRNA library is transfected into this cell line. This approach has several advantages:
1.Increased Editing Efficiency: The independent and stable expression of Cas9 protein and sgRNA on different vectors enhances editing efficiency.
2.Flexibility: Vectors can be designed and constructed flexibly based on experimental needs, such as loading two sgRNA expression cassettes into one vector.
3.Increased Viral Titer: By splitting into two plasmids, the load on each plasmid is reduced, facilitating viral packaging and increasing yield and titer.
4.Increased Stability: Independently constructing a stable Cas9 cell line ensures that the Cas9 expression levels and editing efficiency in each cell are approximately the same, enhancing experimental accuracy.

Traditional CRISPR/Cas9 technology achieves gene editing by introducing double-strand breaks at the target DNA site and then using the cell’s homologous recombination repair mechanism. This approach carries multiple risks, such as lower editing efficiency, reduced homozygous mutation rates, and random insertions or deletions. Prime Editing, however, does not require double-strand breaks. With its Cas9n-RT editing enzyme system and pegRNA, Prime Editing achieves more accurate and safer gene editing with reduced off-target effects.

During vector amplification, Escherichia coli (E. coli) strains are typically used. The commonly used strain for most non-recombinant vectors is DH5α, which is suitable for most applications. For recombinant vectors, such as lentiviral vectors and transposon vectors, the Stbl3 strain can be used for amplification. Stbl3 is a specialized E. coli strain derived from HB101, which has a mutation in the recombinase gene recA13, effectively suppressing recombination of long fragment terminal repeat regions and reducing the likelihood of erroneous recombination.

1.The design process can follow these steps:
1.Identify the target gene sequence.
2.Specify the Cas protein being used. Different Cas proteins require corresponding PAM (Protospacer Adjacent Motif) sequences; for instance, Cas12a needs the "TTTV" PAM sequence for target recognition.
3.Select the crRNA targeting region. Choose a 20 nt nucleotide sequence on the target gene that is adjacent to the PAM site and pairs with the complementary strand of the crRNA.
4.Combine the selected 20 nt target sequence (variable part) with the scaffold sequence (fixed part) to design the crRNA sequence.
5.Use online tools such as CRISPR design tools (e.g., CRISPOR, Benchling, etc.) to assist in designing crRNA. These tools can predict the efficiency and specificity of the sgRNA, helping to avoid potential off-target effects.
6.After completing the design, the synthetic crRNA sequence can be ordered from a synthetic biology company.

KO cell lines are used for in vitro experiments, suitable for high-throughput screening and cellular studies, while gene knockout animal models are used for in vivo experiments to study gene functions within an entire organism and its interaction with the environment.