Biology Modules 6-8: Genetic Change and Disease

Biology Study Notes: Test Preparation

• The biology test takes place on March 21st and includes modules 6, 7, and 8.
• Module 6 focuses on genetic change, module 7 on infectious disease, and module 8 on non-infectious disease and disorders.

Mod 6: Genetic Change

• Mutation introduces new alleles into a population.
• Mutagens can induce mutations, including electromagnetic radiation sources, chemicals, and naturally occurring mutagens.
• Mutagen is an environmental agent that damages DNA.
• Electromagnetic Radiation (ER) waves carry electromagnetic energy.
• UV light, X-rays, and Gamma rays can cause mutations; Uranium-236 releases Gamma rays.
• Chemicals can be accidentally incorporated into DNA, and can insert themselves into DNA and make gaps.
• Mycotoxins produced by mushrooms and substances produced by plants can be naturally occurring mutagens.

Point Mutations

• Point mutation refers to a change in only one nucleotide.
• Frameshift point mutations include insertion and deletion
• Insertion: Inserting or deleting a single base affects every codon after the mutation.
• Substitution: Mutation of one nucleotide can code for a different amino acid.
• Sickle cell anemia, for example, is a genetic disorder where people have misshapen red blood cells.
• GAG mutating to GTG results in hemoglobin folding into an abnormal shape, hemoglobin molecules clumping together, and inefficient oxygen carrying.

Chromosomal Mutations

• Chromosomal Mutations is any change in the arrangement or structure of a chromosome.
• Deletion: A section breaks off and is lost.
• Inversion: A section breaks off, flips around, and reattaches.
• Translocation: A section breaks off and sticks to a different chromosome.
• Duplication: A section is accidentally copied more than once.
• Non-disjunctions: Chromosomes don't separate properly.
• Effects include chromosomal breakage in the middle of the gene, which may be destroyed.
• Down Syndrome is a genetic disorder where an individual has 3 copies of chromosome #21, caused by a non-disjunction mutation.

Somatic vs Germ-Line Mutations

• Somatic mutations affect only daughter cells.
• Offspring are unaffected by somatic mutations. Ex: lung cancer
• Germ-line mutations change the DNA of a germ cell.
• Germ-line mutations can be passed to offspring, but the parent is unaffected, ex: Down Syndrome.
• Germ cells divide to form sex cells and includes the DNA of a germ cell.

Module 7: Infectious Disease

• Diseases are transmitted in a variety of ways.
• Pathogens cause a variety of infectious diseases. Includes microorganisms, macroorganisms, and non-cellular pathogens.
• Investigate modes of transmission of infectious diseases, including direct contact, indirect contact, and vector transmission.

Types of Pathogens:

• Bacteria (prokaryotic, unicellular organisms): Tuberculosis, tetanus (humans), crown gall (plants)
• Fungi (eukaryotic, non-photosynthetic organisms with a cell wall): Athlete's foot (humans), Chytridiomycosis (frogs), stem rust (plants)
• Protists (eukaryotic, unicellular organisms without a cell wall):. Malaria (humans), Phytophthora dieback (plants)
• Viruses (non-cellular, non-living entities):. Influenza (humans), Ross River fever (humans), Tobacco mosaic virus disease (plants)
• Prions (infectious proteins): Kuru, Creutzfeldt-Jakob disease
• Macroscopic parasites (multicellular pathogens seen with the naked eye): Ticks, fleas, tapeworm

Methods of Transmission

• Direct contact is physical contact between infected and susceptible organisms allowing transfer of infected bodily fluids.
• Indirect contact spread through intermediates like air, water, food and contaminated objects.
• Vectors are other organisms that carry disease from one host to another. Example: malaria spread by female mosquitoes.

Epidemics

• Epidemics occur when the number of disease cases are above normal in a specified area.
• Large Area is Pandemic; Small area is Epidemic
• Factors that contribute to epidemics include pathogenic factors and human factors.
• Control methods include identifying the pathogen, environmental management, and quarantine.
• Pathogen virulence, mutations, and antibiotic resistance contribute to epidemics.
• Toxins produced by some pathogens make it easier for them to spread and make hosts more susceptible to infection.
• Poor infrastructure can influence epidemics because densely packed populations and lack of clean amenities increase exposure.
• Increased migration and global travel can present a significant problem in epidemics and can even lead to the shift from epidemic to pandemic.

Koch & Pasteur

• Koch proved that Bacillus anthracis is the cause of anthrax.
• Extracted the bacterium from an infected sheep, and injected it into a mouse, which developed the disease.
• Koch's postulates are a list of criteria to prove that a particular organism causes a specific disease.
• The suspected pathogen must be present in every diseased individual and absent in healthy individuals.
• The suspected pathogen must be able to be isolated from the host and grown in pure culture.
• A healthy potential host must develop the same symptoms as the original host when inoculated with the suspected pathogen.
• The suspected pathogen must be re-isolated from the second host and grown in pure culture, appearing identical to the original culture.
• Koch developed techniques for culturing and identifying microbes, including better dyes and solid agar media.
• Pasteur discovered that one type of microorganism (yeast) was responsible for producing alcohol using sugars and microorganism (lactic acid bacteria) was responsible for contaminating and souring wine.
• Pasteur showed that heating liquids to 60-100°C for several minutes killed most microorganisms, a technique called pasteurization.
• Pasteur proved the germ theory of disease and disproved spontaneous generation using his swan-neck flask experiment.
• Pasteur discovered how to make vaccines by administering weakened versions of the pathogen to susceptible individuals
• Pasteur developed vaccines for chicken cholera, anthrax, and rabies.

Types Of Pathogens & Infectious Diseases

• Pathogens invade a host, evade the immune defenses, reproduce, and cause damage to tissues. A pathogen is an agent that causes disease and classified based on their biological structure.

Modes of Transmission

• Occurs when a pathogen is passed through physical contact with an infected person in Direct Contact. Example can be through:
  • Skin-to-skin: Staphylococcus aureus (causes boils).
  • Mucosal membranes: Herpes simplex virus (cold sores).
  • Sexual contact: HIV, syphilis.
• Indirect Contact
  • Pathogens spread via contaminated surfaces, objects, or fomites (e.g., shared utensils, doorknobs). Example:
  • Influenza virus can survive on surfaces for hours, infecting anyone who touches them and then their face.
• Vector transmission involves an intermediate organism (vector) that carries and transmits the pathogen. Example:
  • Mosquito (Anopheles): Transmits Plasmodium (malaria).
  • Tick (Ixodes): Transmits Borrelia burgdorferi (Lyme disease).

Koch & Pasteur

• Koch developed the germ theory of disease: Specific microorganisms cause specific diseases. Developed Koch's Postulates:

  • The microorganism must be present in all cases of the disease.
  • It must be isolated and grown in pure culture.
  • The pure culture must cause the disease when introduced into a healthy host.
  • The microorganism must be reisolated from the newly diseased host and identified as identical to the original. Example: Identified Bacillus anthracis (anthrax). Identified Mycobacterium tuberculosis as the cause of tuberculosis.

• Pasteur showed that microorganisms are responsible for food and liquid spoilage. Developed the "Swan-Neck Flask Experiment"

  • Designs a flask with a long, curved neck to prevent airborne microorganisms from contaminating sterile broth. Result: Broth remained uncontaminated until the neck was broken, disproving spontaneous generation. Developed pasteurization (heat treatment to kill microbes). Created vaccines for rabies and anthrax.

Causes and Effects of Diseases on Agricultural Production

• Plant diseases caused by pathogens (fungi, bacteria, viruses, and nematodes) have significant impacts on crop yield, quality, and economic stability.
• Diseases affecting livestock have profound consequences for agricultural productivity, food supply, and global trade.

Plant diseases

• Rust Diseases (wheat rust caused by Puccinia spp.): Spread via spores, reduces photosynthesis, weakens structure, and reduces yields.
• Phytophthora blight (caused by Phytophthora infestans): Affects potatoes and tomatoes, leading to the Irish Potato Famine.
• Crown Gall Disease (caused by Agrobacterium tumefaciens): Forms galls disrupting nutrient and water flow; stunts growth and reduces productivity.
• Barley Yellow Dwarf Virus: Spread by aphids; stunts growth, yellows leaves, reduces grain yield.

Animal Diseases

• Anthrax (caused by Bacillus anthracis): Infects grazing animals, spreads via contaminated soil; high mortality may also infect humans through contact or consumption.
• Brucellosis: Affects cattle, goats, and pigs; reduces fertility and milk production.
• Foot-and-Mouth Disease: Affects cloven-hoofed animals, spreads via direct contact or contaminated air; causes weight loss, reduced milk yield, and trade restrictions.
• Liver Fluke (Fasciola hepatica): Parasitic worms affecting livestock; spread by consuming infected vegetation in wet pastures; causes liver damage, weight loss, and lower reproductive rates.
• Diseases can reduce the availability of animal-based foods like meat, milk, and eggs.
• Disease outbreaks can lead to export bans and disrupting global supply chains.
• Control strategies include: breeding resistant varieties, vaccination programs, quarantine/biosecurity measures, environmental management.
• Using specific fungicides and antimicrobials to manage outbreaks and prevent parasitic buildup in livestock pastures with rotational grazing.

Pathogen adaptations

• Enzymes break down host barriers. ex: Streptococcus pyogenes secrete hyaluronidase to degrade connective tissue.
• Adhesion is the use of surface proteins to stick to host cells, ex: Influenza virus binds to respiratory cells.
• Survival outside the host, involves Spores, which allow bacteria, for example- Clostridium difficile, to persist.
• Manipulation of Host Behavior to increase transmission of infection. ex: Rabies virus causes aggression in infected animals to increase the rate of spread.

Plant and Animal responses to pathogens

• Plants thicken cell walls (lignification) around the infection site and form necrotic zones to isolate the pathogen and produce phytoalexins and chitinase to inhibit fungal growth. ex: Eucalyptus
• Wheras responses in wheat see pholem blocked to prevent virus systemic spread. There is a Activation of RNA silencing mechanisms with Small RNA molecules to degrade viral RNA. Increased production of salicylic acid, triggering systemic acquired resistance (SAR) across the plant.

Animal Repsonse to pathogens

• Animals use Barriers to pathogen entry, such as the Skin and mucous membranes.
• And Cellular Responses like phagocytosis or Inflammation.
• Damaged tissues release histamines to dilate blood vessels to recruit immune cells to infection site. Apoptosis is programed cell death to prevent pathogens replicating.

Animal chemical changes and Immunity levels

• Innate includes include Complement system proteins that lyse bacterial membranes. And Cytokines signaling molecules (e.g., interleukins) to recruit immune cells and promote inflammation.
• Adaptive immunity is divided in to antibody production where cells produce antibodies that bind to pathogens and T cells (cytotoxic t cells destroy infected by releasing perforin and granzymes.
• Other key responces are fever raised bodies temperature to inhabit pathogen replication. Or interferons: protein released by virus to warn neigh boring cells.

human immune system response to a pathogen.

• Innate and Adaptive Immune Systems. Where Innate system involves non-specific and Immediate responses. Innate is 1st line of defense - Physical barriers, such as skin, mucous membranes and Cilia and then chemical Barriers using Lysozyme and acidic Ph - cellular defense using Phagocytes and Natural killer cells to inflamarte - Finally the Complemented stream Adapitve immune system. Is specific an had memory (2nd line of defence)
  • Using T cells and B cells

to prime to combat antigens

• 1 Active innate immunity - Pathogen detected - Pathogens are engulfes
• 2 then Antigen presentation - Aided by t Cells and MHC molecules
• Then Adapt immune - Humoral Immunity (B Cell Response B cells differentatiate and cellular Immunity (T Cell Response Cytotoxic T Cells detron - Phathogen dies: and memory -Memory B and T cells remain

Prevention, Treatment, and Control of Infectious Diseases

• Factors That Limit Infectious Disease.

• There is variety of factors. human mobility, climate, global trade, and cultural practices. Example: Malaria is in tropical climates with poor sanitation and high mosquito populations while Dengue is the spread is due to human urbanization/ trade.

• In addition: Herd immunity reduces the spread of disease in a population if enough people are immunized via Portions That Are Immune Or Immunised.

• Mobil people can have the Diseases acrosse borders.

Produeces

• Proper hygiene (hand washing and sanitization) is a major control method. Quarantine to isloate indervidual.
• Vaccations such as active (measles vaccine ) and passive immunization. (breast antibodies)
• Health campaigns(anti=smoke.vax drive)
• Pesticides for vector control
• Genetic engineeering
• Pharmathuical for treatment (antiviral antibotics)

Data

• Monitor new cases of infection called incidence. Preverlance means totals across both

historiccal aporach

- Use the WHO to eradiate a vaccine
- Black plagues introduce quarantine

cultural apporch

• Use traditional for antibacterial

Module 8: Non-Infectious Diseases and Disorders

Homeostasis

• Maintaining an organism’s internal environment in response to a changing external environment.

• Through feedback loops, using Temp and glucos and Stimulus-response models body's way of detecting external or internal environmental changes.

Theregulation

• The regulation of an animal's body temperature through 5 changes

How Responds work

• Detect drop in temp
  • Piloerection goosbunnps -Hairs trap air close to the skin
  • Vasoconstriction -Blood vessels constrict, So less blood travels near the skin's Surface
  • Shivering
    • Muscle cells perform respiration in order to break down glucose and make energy while releasing head
  • Increasing metabolism
    • Main Source of heat production when the body is at rest to heat

How respond to heat

• vasodilatation . - blood atcivity loses heat to external envio
• Sweating
• Draws heat from the skin
  • Decreases metabolism

Homeostatic glucose control

• Glucose MUST be stablle3.5-8mmol/L
• Mainoted by pancrease
• Excess glucose and glucagon and unsuling
• Glocasgon peptide. Releas byalpha

what are plants adaption

- Xero plantes in dyr enivroteenmes
    - Reduce somata ect

Halophytes salt tolerant - Excretion - Exclusion

the Nervous system.

That Helps maintain homeostasis and allows organisms to take information from the external environmnet to respond to a set system

• CNS gathers info and coorninates responsces
• PNS carries somatic and autonomic responce

Neurons

- Sensory. Elecric signals

• MOtoor. To glands organe effor
  • Intherneuron

the Endocrine system

Gland secetre hormines: that relaly receptors and reponds and diffes throgh gland and target tissue:

• Includes

4. Thyroid
5. Thymus
6. Pancreas
7. Arenal
8. Gonad
9. Hypothalamus
10. Pituitary
11. Pineal

types

Nerrbous v Endocrine.

Nrerbous is elc and faster and Enderine is horomin

why so manny daiths

• Altered expresisons like cf

• Enivrnmenal fact

• Cancer

• Altered expresisons in cf

the collect represe

Nutriion diseas
Eniornmnetal

• What is

  Distrution Patterns and disasrs

why epidenmolgy

Anayls patterns of non enfec diseases