Pathogens, Genetic Modification, and Disease Classification

Understanding Pathogens: Viruses and Bacteria

Infectious diseases are caused by various pathogens, primarily viruses and bacteria, affecting different systems of the human body. Below is a summary of common diseases, their classification, and typical symptoms.

Common Viral Infections

• Influenza (Flu)

  System Affected: Respiratory System

  Classification: Virus

  Symptoms: Fever, body aches, tiredness, and cough.

• Herpes Simplex Virus (HSV)

  Classification: Virus (DNA)

  After the initial infection, the virus remains inactive in the human body and later reactivates under certain circumstances, such as stress, menstruation, or temperature changes. Symptoms are highly variable, and herpes lesions can appear anywhere on the body.

• Human Immunodeficiency Virus (HIV)

  System Affected: Lymphatic System

  Classification: Virus

  Symptoms: Headache, fever, diarrhea, nausea, and vomiting.

• Eastern Equine Encephalitis (EEE)

  Classification: RNA Virus

  EEE is a rare viral disease spread by mosquitoes that can affect both people and horses. Most people bitten by an infected mosquito will not develop symptoms. However, when symptoms appear (including headache, high fever, chills, and vomiting), the illness may progress rapidly, potentially leading to coma.

• Adenovirus

  Classification: DNA Virus

  This viral disease was first identified in human adenoid tissue. Symptoms include colds, pneumonia, fever, and diarrhea.

Common Bacterial Infections

• Salmonella

  System Affected: Digestive System

  Classification: Bacteria

  Caused by food intoxication. Symptoms typically occur 8 to 72 hours after exposure and include nausea, vomiting, and diarrhea.

• Tetanus

  System Affected: Skeletal/Muscular System

  Classification: Bacteria

  Tetanus is a serious bacterial disease that affects the nervous system. Symptoms include fever, sweating, elevated blood pressure, and a rapid heart rate.

• Streptococcus (Strep Throat)

  Classification: Bacteria

  This bacterial infection causes inflammation and pain in the throat. Symptoms include fever, headache, sore throat, and difficulty swallowing.

Studying the Virus Life Cycle

The study of the virus life cycle involves tracking its stages: entrance, traffic, and exit. Researchers utilize advanced techniques, often involving immunocytology using in vivo cells, to observe these processes.

Virus Tracking Techniques

1. Technique 1: Genetically Modified DNA Tracking

   This method uses genetically modified DNA that produces phosphorescent proteins, which mark specific viral structures. The movement is captured using time-lapse microscopy.

2. Technique 2: Chemical Labeling

   This technique involves using chemical labels (phosphorescent dyes) applied directly to the virus. A lyophilic dye targets the viral envelope, while an amino-reactive dye targets the spike proteins. This method is often costly, and sometimes the virus does not successfully incorporate the chemicals.

Genetically Modified Organisms (GMOs) and Genetics

How Genetically Modified Crops Are Created

1. Identify an organism with the desired characteristic.
2. Remove the specific gene (a length of DNA) that produces this protein.
3. Transfer this gene into the plant intended for protection. This is done either by firing the gene into the plant using a special gene gun, or by utilizing a soil bacterium to insert the gene into the plant.
4. Plant cells that successfully take up the new gene are grown into full-size plants. These plants are rigorously checked to ensure they develop normally and are safe.
5. Alternatively, instead of adding new genes, a gene already present in the plant can be switched off, switched on, or altered to improve a specific characteristic. For example, in fruit, a gene can be switched on to slow down ripening, thereby reducing harvest damage.

GMO Approval in South Africa

In South Africa, GMOs must be approved by the national government before they can be used. Crops currently approved for production include:

• Insect-tolerant and herbicide-tolerant maize (yellow & white)
• Insect-tolerant and herbicide-tolerant cotton
• Herbicide-tolerant soya

Key Genetic Terminology

• Gene: A segment of DNA which produces a specific characteristic.
• Gene Locus: The location on homologous chromosomes where two genes giving the same characteristic are found.
• Alleles: The specific forms or variations of a gene found at a particular gene locus.