The scenarios where nucleic acid extraction and purification kits can be used are as follows:

I. Medical Field

1. Clinical Diagnosis
   • Diagnosis of Infectious Diseases: It is used for detecting pathogen nucleic acids. For example, when diagnosing viral infections (such as COVID – 19, influenza virus, hepatitis B virus, hepatitis C virus, HIV, etc.), bacterial infections (such as Mycobacterium tuberculosis, Streptococcus pneumoniae, etc.), and fungal infections (such as Candida), nucleic acids are extracted and purified from samples such as patients’ blood, sputum, throat swabs, and urine. Subsequent nucleic acid detection techniques (such as PCR) are used to determine the presence of pathogens, assisting doctors in accurate disease diagnosis.
   • Diagnosis of Genetic Diseases: For some genetic diseases caused by gene mutations, such as thalassemia and cystic fibrosis, DNA is extracted from samples such as patients’ blood, amniotic fluid (for fetal testing), and chorionic villus tissue for genetic analysis to help diagnose diseases and assess genetic risks.
   • Tumor Diagnosis: In cancer diagnosis, nucleic acids can be extracted from samples such as tumor tissues and blood (for detecting circulating tumor DNA). For example, by sequencing the DNA extracted from tumor tissues to find specific tumor – related gene mutations, which helps to determine the type and stage of the tumor and formulate treatment plans. Detecting circulating tumor DNA in blood can be used for early cancer screening and monitoring tumor recurrence.
2. Disease Monitoring and Prognosis Evaluation
   • During the treatment of some chronic diseases (such as chronic hepatitis B and C), nucleic acid extraction and purification kits are regularly used to extract viral nucleic acids from patients’ blood to monitor changes in viral load and evaluate treatment effects and disease prognosis. For organ transplant recipients, donor – specific nucleic acids in the blood are detected to monitor whether there is transplant rejection.

II. Biomedical Research

1. Gene Expression Research
   • In cell and molecular biology research, RNA is extracted from cultured cells (such as cancer cell lines, stem cells, etc.) or tissue samples. Through techniques such as reverse transcription – polymerase chain reaction (RT – PCR), gene chips, and RNA sequencing, the changes in gene expression levels under different physiological and pathological conditions (such as cell differentiation, stress response, disease occurrence, etc.) are analyzed to understand the functions and regulatory mechanisms of genes.
2. Gene Cloning and Editing
   • In the field of genetic engineering, high – purity DNA needs to be extracted from biological samples for cloning specific genes. For example, when constructing a gene library, target genes are extracted from genomic DNA and inserted into vectors for cloning and expression. In the application of emerging gene – editing techniques (such as CRISPR – Cas9), high – quality DNA is also required for the design and implementation of gene – editing operations. Nucleic acid extraction and purification kits can ensure the acquisition of DNA samples that meet the requirements.
3. Drug Research and Development
   • During the drug research and development process, the effects of drugs on gene expression and functions of cells or organisms are studied. For example, in drug – screening experiments, nucleic acids are extracted from drug – treated cell or tissue samples, and relevant gene changes are analyzed to evaluate the efficacy and mechanism of action of drugs.

III. Forensic Medicine

1. Individual Identification and Paternity Testing
   • Nucleic acids are extracted from biological samples (such as blood, semen, hair, saliva, etc.) collected at crime scenes or relevant samples in civil cases. Through techniques such as DNA fingerprinting and short tandem repeat (STR) analysis, individual identification is carried out to determine criminal suspects or solve paternity disputes.

IV. Food Safety

1. Detection of Pathogenic Microorganisms
   • In food production and supervision processes, it is used to detect pathogenic microorganisms in food. For example, nucleic acids are extracted from foods such as meat, dairy products, fruits, and vegetables to detect the presence of harmful bacteria such as Salmonella, Escherichia coli O157:H7, Listeria, and food – borne viruses such as Norovirus, ensuring food safety.
2. Detection of Genetically Modified Foods
   • Genetically modified foods are tested. Nucleic acids are extracted from food samples, and by detecting specific transgenic sequences, it is determined whether the food is genetically modified and whether the transgenic components comply with relevant regulations and standards.

V. Environmental Monitoring

1. Analysis of Microbial Communities
   • In environmental science research, microbial nucleic acids are extracted from environmental samples such as soil, water, and air. Through high – throughput sequencing technology, the structure and diversity of microbial communities are analyzed to understand the distribution and ecological functions of microorganisms in the environment and evaluate the degree of environmental pollution and the health status of ecosystems.