4. The year is 2442. Protein engineering and molecular biology have became incre

Question

4. The year is 2442. Protein engineering and molecular biology have became incredibly powerful and all diseases are cured. You are still on vacation with your clone, and are pondering the differences between the cat that you just spontaneously adopted and other organisms.

A. Name two important cells in the cat's adaptive immune system, and describe a difference between the two cells.

B. Many bacteria also live inside the cat. How do the bacteria use CRISPR-Cas9 to protect themselves from invading pathogens? In describing this, name what type of molecule it targets and how this can be used to protect against specific pathogens. Also clarify what the names “CRISPR” and “Cas9” refer to.

C. After a long and contentious conversation, you two decide to work towards making a transgenic cat that expresses abnormally huge amounts of motor proteins in every cell. All cells in the cat must be genetically identical for the cat to be fully transgenic, and you want to use CRISPRCas9 to accomplish this. Your clone is really high and thinks that feeding Cas9 (with necessary guide RNA and DNA for insertion) to your cat will make this work. Name one reason why your clone is wrong.

Explanation / Answer

A. T-cells and B-cells are the two major cells involved in a cat's adaptive immune system. The T-cells are involved in cell mediated immunity while B-cells are involved in humoral immunity. T-cells recognise antigens on its cell surface and present it to major histocompatibility molecules (MHC) and process it further by presenting the cells to the B-cells where the antigen is fragmented to small peptides. When this antigen is contacted again, seconday antibodies are released against it. The cat is said to get adapted to the previously encountered antigen.

B. Crispr/cas9 is mainly used to knockout and knockin certain genes. Bacteria can use this to kill pathogens by degrading the genome of the organisms by removing genes. Crispr is a family of DNA sequences present in bacteria which are targeted to destroy the DNA of organisms. Cas9 (crispr associated nuclease-9) is a nuclease enzyme that fragments DNA. It identifies certain sequences belonging to pathogenic bacteria and degrades it.

C. Inserting cas9 to the cat is a wrong idea as it is a nuclease enzyme, it may degrade the DNA of the useful bacteria too. If all the cells express cas9, there are chances all the DNA in the cells will be fragmented. A controlled targetted expression of cas9 is required in order to prevent all the cat's DNA from being damaged. If it is expressed in all cells, all the DNA of the useful bacteria as well as the organism itself will be destroyed. Thus, conditional transgenic is a better option to generate a trangenic cat.

Reference:

https://www.horizondiscovery.com/gene-editing/crispr-cas9

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