15.1
What is Genetic Engineering?
Genetic engineering is the process of modifying an organism’s DNA to introduce new, desirable traits. Many organisms, from bacteria to plants and anim…
Genetic engineering is the modification of an organism’s DNA.
This process involves modifying the nucleotide sequence of a gene using genome editing techniques, such as CRISPR-Cas9.
CRISPR uses a guide RNA to find a specific DNA region.
Then, the Cas9 enzyme cuts the DNA at the specific sequence targeted by the guide RNA. This allows scientists to alter the DNA sequence in different ways.
One type of genetic change is gene knockout, or deletion, in which a targeted gene is disrupted or removed. This prevents the organism from producing a functional protein.
Alternatively, scientists can insert a new gene from another organism into the DNA, allowing the organism to produce a new protein.
For example, a gene from a spider can be inserted into a goat’s DNA, creating a transgenic goat that produces spider silk protein in its milk, which can be purified for biomedical and industrial applications.
Similarly, in gene therapy, a functional gene can be introduced into a patient’s cells to replace a defective gene. This enables the cells to produce a functional protein, which may help treat a genetic disease.
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Q1: How does CRISPR/Cas9 work as a genome editing tool?
CRISPR/Cas9 functions as molecular scissors that cut DNA at specific locations. Guide RNA sequences direct the Cas9 enzyme to target sites in the genome, allowing scientists to add, remove, or alter genetic material with precision. This system originated as a prokaryotic immune response and has been adapted for editing genetic information in research and therapeutic applications.
Q2: What is the difference between a knockout and a knockin in genetic engineering?
A knockout removes a gene from an organism's genome, eliminating its function entirely. A knockin introduces a new gene into the genome through gene targeting, which relies on homologous recombination—genetic exchange between DNA molecules sharing similar sequences. Both techniques modify endogenous genes but achieve opposite outcomes: deletion versus insertion.
Q3: How can gene therapy treat genetic diseases?
Gene therapy introduces a new gene into a patient's cells so the protein it encodes can be expressed and function properly. Scientists often use modified viruses to deliver correct copies of defective genes to diseased cells. This approach provides potential cures or treatments for serious genetic disorders like Severe Combined Immunodeficiency (SCID) that were previously untreatable.
Q4: What are transgenic organisms and how are they created?
Transgenic organisms contain genes from another species inserted into their genome, creating recombinant DNA. Scientists combine DNA from different sources and introduce it into a host organism, which becomes a genetically modified organism (GMO). Examples include transgenic goats producing spider silk in their milk and plants modified for improved nutritional content and pest resistance.
Q5: Why is human germline editing considered ethically problematic?
Germline editing modifies reproductive cells, so genetic changes are inherited by offspring and affect future populations. Most gene therapies modify somatic cells, affecting only the individual treated. The 2018 case of allegedly gene-edited babies sparked global concern about unintended health consequences, effects on future generations, and the broader implications for humanity.
Q6: What practical applications does genetic engineering have beyond medicine?
Genetic engineering has transformed agriculture and industry. Plants are genetically modified to enhance nutritional content and pest resistance, with nearly 450 million acres of GM crops grown globally. Transgenic animals produce valuable proteins for industrial use. Bacteria were the first genetically engineered organisms, modified to produce synthetic insulin for diabetes treatment and other therapeutic proteins.
Q7: Why is the universal genetic code important for genetic engineering?
The genetic code and DNA structure are universal across all life forms, enabling scientists to transfer genes between different organisms. This universality allows researchers to insert genes from one species into another and have them function properly. This principle underlies the creation of transgenic organisms and the success of genetic engineering across bacteria, plants, and animals.