Human Health and Disease

genetic

defective genes can lead to an inability of the body to produce proper proteins or structures in the body (E.g. Haemophilia)

Infectious

transmitted in four different ways:

• direct

• fomite

• zoonotic

• vectors

direct

people to people (E.g. conjunctivitis, Hepatitis A and B)

fomite

surface to people (E.g. cold sores, hand-foot-mouth disease)

zoonotic

animal to people (E.g. rabies, psittacosis)

vectors

using small organisms to transmit bacteria or viruses (E.g. Lyme disease, tick-borne encephalitis, west Nile virus)

virus structure

the simplest virus structure consist of two basic components: nucleic acid (single or double stranded RNA or DNA) and a protein coat, the capsid.

capsid

functions as a shell to protect the viral genome from nucleases and during infections attaches the vision to specific receptors exposed on the prospective host cell.

DNA

double-stranded molecules that has a long chain of nucleotides.

RNA

single-stranded molecule which has a shorter chain of nucleotides.

genetic material

any material of plant, animal, microbial or other origin that carries genetic information and that passes from one generation to the next.

not living virus particles

• contains genetic information → DNA or RNA

• replicate only with the help of living cells

• does not have any metabolic processes

• do not consume food or produce waste

• do not grow

Intracellular Pathogen

organisms that are capable of growing and reproducing inside host cells.

Lytic Cycle

• the virus invades a host cell and injects its DNA (or RNA) into the host

• the host cell replicates the parts of the virus and other materials in viral DNA

• New viral particles are assembled in the host cells

• cell lysis (death) occurs releasing new viruses )E.g. common cold or flu)

Lysogenetic Cycle

• upon infection the viral genome becomes integrated into that of the host

• as the host cell undergoes cell cycle and cellular synthesis the viral DNA is copied and incorporated into all of the newly synthesised cell

• after a prolonged period of time a trigger causes the switch to lytic cycle and a full blown infection occurs.

• E.g. chicken poxes can manifest into shingles later in life.

Evolution of Viruses

• RNA viruses have the capacity to mutate quickly

• they can pick up genetic information from the host cell

• there can be random errors that happen in the replication process of the RNA that own lead to change in the protein coat of the virus. This can make it easier for the virus to enter cells and/or make it harder for the immune system to detect the virus as a foreign particle.

  • significane → virus evolution impacts all life and viral emergence continues to threaten human health.

Aerobic

requires oxygen, releases more energy but slowly

Anaerobic

respiration access without oxygen and releases less energy but more quickly

Conjugation

process by which one bacterium transfers genetic material to another through direct contact.

Binary Fission

process of one cell simply dividing into two

Gram+

positive bacteria show blue or purple after straining in a laboratory test. They have thick cell walls.

Gram-

bacteria shows pink or red on staining and have a thin cell wall.

Cellular Structure of Bacteria

the cell wall forms a rigid structure of uniform thickness around the cell and is responsible for the characteristics shape of the cell.

Value/Important of Bacteria

• helps you digest food → produces vitamins (E.g. vitamin K)

• protects against infection → e.g. commensal bacteria

• maintain your reproductive health → e.g. cervicovaginal lactobacillus

How bacteria cause illness or disease

• Septicaemia → if bacteria spreads in a person may become septic and die from a bacterial infection

• many bacteria produce specific surfaces proteins or toxins which may hurt the organism lives on or in.

How bacteria is cultured in the lab

Take a sample of something, for example ocean water and dilute it in water. Then spread a droplet of this dilation on a peak: dish full of nutrients. Each individual bacterium lands in a unique spot on the dish.

Independent Variable

the variable you manipulate, control, or vary in an experimental study to explore its effects.

Dependent Variable

what you measure in the experiment and what is affected during the experiment.

Controlled Variable

anything that is held constant or limited in a research study.

How bacteria evolves

• amplified by bacteria’s ability to mutate and exchange genetic information from other bacteria

• genetic combination can change through conjugation and gene transfer

• a bacteria can cut out a gene, package it as a plasma and send it to another bacteria cell giving that bacteria antibiotic resistance as well.

principle of evolution of bacteria

• bacterial diversity exists in a bacterial community

• only the bacteria with certain characteristics survive the use of antibiotics. We would say that these bacteria are “fit”.

• This results in a loss of genetic diversity. Only these bacteria that survive reproduce. The next generation of bacteria now are all antibiotic resistant.

Bacteria replicate

rapidly using a special form of mitosis called Binary Fission. (this can occur every 8 to 20 minutes)

HIV capsid

HIV’s core that contains HIV RNA

HIV envelope

outer surface of HIV

HIV enzymes

proteins that carry out steps in the HIV life cycle.

HIV RNA

HIV’s genetic material

cladistics

use shared characteristics to establish evolutionary relationships.

evolutionary events

the appearance of a new characteristics → These characteristics are assumed to be due to new forms of the genes that then get passed down to all successive generations.

In-group

share characteristics

Out-group

do not share characteristics

Nodes

represent an ancestral form of the species

Clades

are groups of species based on their evolutionary relationship.

Mutations

• every time the viral DNA is replicated copying errors can occur

  • this leads to genetic mutation that will be prevalent in all future replications of the virus

  • by doing genome comparison between different viruses scientist can show the relatedness of viruses and generated phylogenetic trees mapping out the evolution of viruses

Significance of Antibiotic Resistance

• medicines become ineffective and infection becomes difficult or impossible to treat.

  • increasing the risk of disease spread

Differences in the activity of bacteria and viruses and how they make you sick.

Bacteria:

• multiply so rapidly, they crowd out host tissues and disrupt normal functions

• kill cells and tissues

• make toxins that can paralyze, or destroy cells.

Viruses:

• cause infections by entering and multiplying inside the host’s healthy cells

• cannot be detected by the immune system

E-coil (caused by bacteria)

food poison from contaminated food (e.g. raw meat)

Parkinson (caused by bacteria)

progressive disorder, which affects the nervous system and the parts of the body controlled by the nerves.

Flesh eating bacteria (caused by bacteria)

it destories skin, fat, and tissue covering the muscles within a very short time span

step throat (caused by bacteria)

spreads through droplets (e.g. a infected person coughs, sneezes, or you share food and drinks). It affect the throat and with antibiotic can heal pretty quickly.

mosquito-borne viruses (caused by a virus)

medium-size viruses like West Nile and transmitted to human by saliva in a mosquito’s bite and travel throughout the body in the bloodstream.

deadly adaptors

large viruses that infect humans, such as variula (which causes smallpox) and Ebola viruses, tend to have a high death rate. This is probably because many large viruses carry viral proteins, in addition to their genes, can overwhelm and shut down the host’s defences.