Task 3 Flashcards
1
Q
artifical insemination
nature
A
manual injection of male sperm into female reproductive tract
used for cattle
used to produce offpsring with favourable characteristics
2
Q
artifical insemination
adv
A
minimises cost of transporting animals together
sperm cell can be frozen and transported
more offpring produced than regular breeding
can inseminite many females
3
Q
Artifical insemination
disadv
A
using method at mass reduces genetic varation
can inseminate many females –> male alleles become more dominant in pop
higher ratio of alleles selected by breeders rather than by nature
4
Q
Artifical pollination
nature
A
manual transfer of pollen dusted upon the stigma of another plant
5
Q
Artificial pollination
Adv
A
Cost effective
Increases genetic diversity through hybrid species –> new
combinations of alleles
Improvs cross breeding
6
Q
Artifical pollinaion
Disadv
A
Overuse leads to reduces genetic diversity
Passing on a limited array of genes/allele combinations –> propogate unhelpful diseases
7
Q
Cloning general
A
Asexual reproduction
Used to create offpsirng gentically identical to parent
Plant cloning and animal cloning
8
Q
Cloning adv
A
Plants and animals with favourable characteristics
9
Q
Cloning disadv
A
Lack of genetic diversity –> susceptible to an entire wipeout by disease or selective pressure
10
Q
In vitro fertilisation general
A
where an egg is fertilised by a sperm outside the mother’s body
in petri dish
resulting zygote is cultured until early stages of development
transferred into surrogate mother uturus
11
Q
IVF adv
A
Advantegous alleles which would not naturally have been passed on can be inhereited by offpsring
12
Q
IVF disadv
A
genetic diversty of population reduced
genes for infertility passed on
sperm banks ca alter genetic composition of population (only desirable traits of sperms listed)
13
Q
Cloning for plants
A
Cutting or grafting a plant
E.g. tissue culture
cutting piece of stem/ root/leaf and culturing in a nutrient medium
14
Q
Animal cloning
A
Dolly the sheep (1990s)
Removing the nucleus from an unfertilised egg and putting nucleus of other animal (donor)
implanting egg into surrogate mother
15
Q
The use of scientific knowledge leads to:
(effect on agriculture manipulation)
A
- asexual techniques eg cloning plants through plant propagation, –> allows the rapid development of plants with known qualities.
- the artificial selection of favourable characteristics in plants, greater diveristy in foods, plants?
- reproductive technologies –> manipulate animal reproduction eg artificial insemination, IVF, whole organism cloning such as Dolly the sheep.
- gene technology or genetic engineering, which results in genetically modified organisms.
16
Q
Varation occurs through
(meiosis processes)
A
- Mutations
- Crossing Over (during Prophase I)
- Independnant assortment (during Metaphase I)
- Process of fertilisation
17
Q
Crossing over
when does it happen
A
the possible exchange of alleles at the chiasma of homologous chromosomes
Prophase I
18
Q
Independent assortment
when
A
the division of homologous chromosomes to seperate poles
Metaphase I
19
Q
chromosomal mutations
A
large scale mutations that affect the overall structure of a chromosome or the entire number of chromosomes in a cell are altered.
20
Q
genes
A
a segment of DNA on a chromosome that determines inherited characteristics
21
Q
alleles
A
alternative forms of the same gene
22
Q
example of autosomal dominant disease
A
huntington’s disease
does not skip a generation
23
Q
exmaple of autosomal recessive disease
A
cystic fibrosis
24
Q
examples of sex linked diseases
A
haemophilia (X linked, females are carriers or affected, all male affected)
colour blindness
25
Purpose of allele frequency data
Understand variation
Predict potential of population to adapt, resilience and survival of species
26
Gene pool
sum total of all the genes and their alleles within a population
27
Genetic diversity
the total of all the genetic characteristics in the genetic makeup of a species
28
population genetics
the study of how the gene pool of a population changes over time and space
29
single nucleotide polymorphism
SNPs
Base substitution mutations (alleles) that commonly occur within the species population (in 1% of species)
30
Uses of single nucelotide polymorphism
genetic marker to determine the population’s susceptibility to a certain disease e.g. asthma, Alziemer’s
help predict an individual’s response to certain drugs,
SNPs at higher frequences used to indicate presence of particular disease
31
Adv of single nucleotide polymorphism
identify cause and effect relatipnship between SNP and disease
Cheapter than sequencing genome
32
DNA sequecning
the process of determining the precise order of nucleotides within a segment of DNA
33
Methods of DNA sequencing
Sanger chain termination method
DNA sequencer
34
Sanger chain termination gerneral
Replicating DNA strands outside of cells with ddNATP attachments that stop the chain from growing/adding upon
35
Sanger chain termination steps
1. Isolate DNA from the cells of the organism
2. Sequence reactions
3. Fragment of DNA produced are then sorted by length using capillary electrophoresis
4. Results are analysed by a computer
36
Factors affecting genetic variation in a gene pool
size of population, mutation, natural selection, genetic drift, diversity of the environment, migration pattern
37
DNA profiling
identify and compare indivduls by characteristics in their DNA
using regions of DNA containing STRs
38
STRs
short sequences of DNA, usually 2-5 base pairs long that repeat numerous times
39
Uses of DNA profiling
Forensics: or crime scenes with fingerprints, although too few loci makes false positives
Paternity studies: can compare possible fathers to confirm or refute paternity using bands of mother and father
Pedigree determination in animals: ensure breeder has gained correct parents for animal breeding using DNA fingerprints
40
uses of population genetics data
conservation genetics (cheetah, pymgy possum)
inheritance of diseases (breast cancer)
41
mutations
permanent change to the DNA sequence of an organism
42
importance of mutations
new variation/alleles increases the chance of a population's survival during environmental change.
Without mutations, natural selection cannot occur.
43
Mutagens
electromagnetic radiation sources
Ionising radiation: breaks chemical bonds causing damage to DNA, many fractures can overwhelm enzymes to cause mistakes in DNA
UV Rays: promote a chemical reaction of bases fusing together e.g. two thymine bases, cause bulge in DNA and disrupt normal transcription and replication
44
Mutagens
chemicals
Intercalating agents: insert into DNA base sequence, causes stretch and DNA polymerase to insert extra base --> frameshift mutation occurs
Base analogous: chemicals with physical structure to nitrogenous bases when incorporated in DNA
Reacting Chemicals: react with the nitrogenous bases and chemically modify the DNA
Example: Carcinogen in cigarrettes
45
Types of mutagens
ionising electomagnetic radiation
chemicals
biological mutagens/naturally occuring
46
Mutagens
naturally occuring/biological
Biological Mutagens: release of free radicals. from metabolism processes, cause oxidation of DNA, breaking DNA strands
Viruses: insert genetic information into chromosomes of host cell, causing disruption to normal cell function e.g. HPV --> oncogenic (cancer causing) virus that causes cervical cancers.
47
Example of point mutation
Sickle cell anemia
48
Mutations
Effect on proteins
Nonsense: changing an amino acid to a stop codon, cutting the protein short. This resulting protein is normally non-functional
Misense: a point mutation that results in 1 amino acid change
e.g. E.g. sickle cell anaemia: CTC changes to CAC, altering amino acuds and shape of haemoglobin
Silent: no change caused in amino acids. (swapped base in the triplet, still coding for the same amino acid)
Frameshift: an insertion or deletion
--> shifts entire reading frame of RNA, creation of a whole sequence of incorrect amino acids and production of a non-functional protein.
49
Chromosomal mutations
Inversion
Translocation
Inversion: a section of DNA is removed, turned 180 and then reinserted into the chromosome so that the bases are in reverse order.
Translocation: a section of DNA is moved from one chromosome to another.
50
Aneuploidy
An extra or missing chromosome
Caused by nondisjunction: failure of homologous chromosomes to separate during cell division
e.g trisomy
51
Causes of mutations
Spontaneous
Induced (mutagens)
52
Polyploidy
more than two haploid sets of chromosomes, e.g. triploidy
53
Effect of somatic mutation
may lead to a localised effect, such as the development of a tumour in a part of the organism, but it will not be passed on to the next generation.
or lead to cell dying, or no effect
54
Effect of germline mutation
becomes incorporated within DNA of every cell within the offspring’s body
55
Exmaple of somatic mutation
skin cancer
56
Example of germline mutation
haemophilia
57
Segments of coding dna
exons (gene)
58
Segments of non-coding dna
enhancers/silencers/regulators
promoters
introns (gene)
59
Exons function
Codes for proteins that carry out biological functions.
60
Introns function
Code for their own removal during mRNA splicing (end of transcription)
61
Promoter function
Tell the enzyme RNA polymerase where to bind RNA to DNA which begins the transcription.
62
Significance of mutation in
Exons
Can directly impact the sequence of amino acids and therefore affect the functioning of proteins.
Changed DNA code = changed mRNA = mutated protein
63
Significance of mutation in
introns
Have the potential to affect splicing of DNA (mutation in introns causes removal of exons = deletion).
64
Significance of mutation in
promoter
Mutation can result in polypeptide chains not being fully transcribed, causing deficient proteins
65
Enhancers/silencers function
signifiance of mutation
Enhancers turn on or enhance the expression of a gene.
Silencers turn off or slow the expression of a gene.
Can cause too much or too little production of proteins or the wrong protein to be produced if turned on.
E.g. diabetics
66
Mechanisms for changein frequency of gene pool
Selective pressures such as predators and mating result in certain characteristics increasing an individual's chance of survival. Therefore unfavourable traits are not passed to the next generation, reducing frequency of this allele in the gene pool
67
Effect on gene pool
Mutations
Increased number of alleles in a population
68
Genetic drift
A random event leading to a change in alleles frequency because some individuals wiped out
Small pop greatly affected
69
Genetic drift
Examples (2)
Founder Effect: a small group of individuals are separated from the main population and become the founding members of a new population. This new population has different allele frequencies to the original population. (Armish have 6 fingers)
ALL BY CHANCE
Bottleneck Effect:
lots of a population died due to random environmental change and by chance certain individuals survived (within this decreased population there is decreased genetic variation)l
70
Effect on gene pool
Genetic drift
Decreased number of alleles in a population
71
Gene flow
individuals with different genes come into a population and spread their alleles
72
Effect on gene pool
Gene flow
Allele frequency changes
73
Biotechnology
the use of living materials, biological processes or biological products to make new products that are useful to humans in field such as industry, agriculture and medicine
74
Past biotechnology techniques
selective breeding
To get desired combinations of favourable characteristics.
It gradually increased yields and selective breeding was soon extended to domesticated animals such as goats, sheep, cattle, horses, chickens.
75
76
past biotechnology techniques
fermentation
use of natural microorganisms
Brewing beer uses a living thing (yeast) to make a new product. Beer renders the water supplies safe to drink and reduces epidemics.
other forms of fermentation led to soy sauce, yoghurt, leavened bread, etc. Many fermentation techniques have the advantage of preserving foods for longer storage.
77
Modern biotechnologies
modern biotechnology appeared in 1971 with the first experiments on gene splicing.
* Medical supplies of human insulin and other substances, using human genes spliced into bacterial cells.
* Genetically modified micro-organisms that clean-up oil spills, or other forms of pollution, and GMOs that manufacture biofuel or biodegradable plastic
78
Selective breeding general
People selected organisms that they wished to cross-breed, ensuring that selected individuals possessed desirable characteristics that could be passed on to future generations.
EG
Crossing a Fresian bull with Jersey cow (large quantities and creamy milk respectively)
79
Selective breeding disadv
Time consuming and costly (transport of animals)
reduces biodiversity as only individuals with desired characteristics are allowed to breed and pass on their genes.
80
Selective breeding adv
Advantageous for a population of organisms to maintaining genetic variability
- provides opportunity for natural selection to operate and evolution to survive
81
Future biotechnologies
Gene therapy general
Replacing a mutated gene that causes disease with a healthy copy
Inactivating a mutated gene
Introducing a new gene to the body to help fight a disease
82
Future biotechnoligies
Gene therapy process
disadv
A new gene added through genticlally engineered virus as vector
And CRISPR Cas 9
Disadv: may lead to extreme immune response like organ failure
Insertion may cause mutation
83
Future biotechnologies
CRISPR Cas 9 case study
concerns:
Genome editing technique
An enzyme that can snip DNA at particular base
Comprised of guide RNA + Cas 9 protein
Genes can be spliced and inserted with accuracy
Ethical concerns: e.g. designer babies, cosmetology
84
Modern biotechnologies
extra
artifical insemination
IVF
Transgenic species (GMO) e.g Bt cotton
85
Whole organism cloning
relica genome of a complete individuall plant or animal
Creating a genetically identical organism using somatic cells from another organism
86
Effect of whole organism cloning on genetic diveristy
reduce biodiversity as cloned organisms are genetically identical to the parent organism. However, this is not used commercially in cattle so will not have a large effect on biodiversity.
87
Animal whole organism cloning
general
Somatic cell nucleur transfer (SCNT)→ offspring genetically identical to one of the parents
Embryo splitting
e.g. First cloned mammal (Dolly the sheep), achieved through adult differntiated udder cell
88
Animal whole organism cloning
Process
1. Cells taken from the udder of ewe (Sheep 1). These cells were starved of nutrients to stop them dividing.
2. The nucleus was removed from a healthy unfertilised egg from another sheep (Sheep 2)
3. The udder cell with a nucleus, from Sheep 1, was injected into nucleated egg of Sheep 2.
4. The two cells were treated with electricity, causing cells to fuse/belnd together to form a fertilixed egg cell.
5. As this cell divided, the resulting embryo was implanted into the uterus of the surrogate mother.
89
Case study on Dolly the sheep
whole organism cloning
implications of it
Uptake of SCNT animal cloning is slow
High costs, low success rate (276 attempts for Dolly), health probelms, higher mortality rate of cloned animals, higher consumer resistance to cloned food
90
Issues with whole oganism cloning for animals
Animal welfare: treatment in large scale farming
Same method could be used for humans, rasing moral, relgious and legal concerns
Religous argument that through cloning humans are acting as God
Unforeseen health risks fo cloned animals
Expensive procedure, which limits access to this technique
91
Whole organism cloning
Adv
Produces offspring genetically identical to organisms with favourable characterstics
Provide higher yield in products (lowering cost to consumers and higher quality of products obtained
Eg. Merino sheep cloning → produce high quality wool
92
Whole organism cloning
Disadv
Lowers genetic diversity and variation of the species population
On mass scale, could lead to mass decline in specie spopulaiton and major loss to farmers
Any mutations can be cloned and transferred to cloned offpsiring, resulting in disease or cancer
Clones die earlier than expected
Expensive → economic limitation on its effectiveness
93
94
Whole organism cloning
Applications
Extinct animals/endangered animals conservation, market changes/demands
Give rise to non-diseased species without specific mutation
Cloning of transgenic organisms
Replacing selective breeding: selected the cloned
Plants: propagate species tht are disease tree (rubarb, potatoes), and transgenic plants, quicker and precise
94
Gene cloning
A gene amplification techique where recombinant DNA is made in vitro and is amplified invivo inside a bacterium
94
Gene cloning
Process
1. Cut out desired gene using restriction enzymes
2. Cut the bacterial plasmid with the same restriction enzymes
3. Use DNA ligase to paste gene into the plasmid
4. Using heat shock, Insert the plasmid into bacteria
5. When bacteria goes through binary fission, they make copies of the gene
E.g. cloned bacteria produce insulin which is harvested for patients with diabetes
95
Gene cloning requires...
Restriction enzymes, DNA ligase, vector DNA and bacterial cells
96
Polymerase chain reaction
(PCR)
definition
used to amplify spceiifc regions of a DNA strand millions of times
97
PCR applications
DNA profiling for forensics
DNA sequencing in the study of genetic disease
Testing for the presence of COVID19 virus
98
PCR materials required
Template DNA
DNA primers
Taq polymerase
Free nucleotides
Occurs in buffer solution: salts and ions that keep polymerase functioning
99
PCR process order
Denauration: seperates template DNA
95C
Hydrogen bonds break
Each cycle needs shorter denaturing time
Annealing: specifies region with primer
Forward and reverse primers
55C-65C depending on length and sequence
Allows hydrogen bonds to form again
Extension: replicating DNA
Uses polymerase
5’ to 3’ direction
72C → optimal temperature for polymerase
100
Functions of primer and bacteria in PCR
Primer: short piece of single stranded DNA that bind to a specific region in the template DNA to flank the target region to be amplified
Bacteria: optimal for PCR as it doesnt denaure at high temp
101
Applications/tehcniques of recombinant technology
case studies
atlantic salmon
bt cotton
102
Atlantic salmon
overview
Salmon with added growth hormone
GM salmon= 61cm, 3kg
Regular salmon = 22cm, 1.3kg
103
Atlantic salmon
transgenic nature
A growth hormone-regulating gene from Pacific Chinook salmoon
AND promotor gene from an ocean pout
Therefore salmon grows to adult size in shorter time
104
Altantic salmon
Transgenic processes
1. Females (non transgenic brood stock) are gently massaged to extrude the non-fertilised eggs (green eegs)
2. Milt (sperm) which carries the AAS transgene is extruded from the male Atlantic salmon
3. Once eggs and milt are fertilised, eggs are pressure shocked to induce sterility
4. The fertilised, sterile, all female AquAdvantage eggs are placed into incubators until they develop and are shipped as ‘eyed eggs’
105
Atlantic salmon
purpose of modification
Increase the speed that fish grow without affecting its ultimate size and other qualities
Fish grows to market size in 16-18 months rather than 3 years
Fish can be farmed year-round in any climate
More production cycles in less time
106
Atlantic salmon adv
(6)
Increase food production
Grows in any climate → less hospitable, warmer waters
Concerve wild fish populations → using 25% less feed than any Atlantic salmon on market today
Low impact fish farming → farmers control water input, discharge, sanitation ability to recycle resources
Reduce carbon emissions → less travel between land-based facilities and stores, emitting 23-25X less CO2
No differences in flavour, nutritional values or flesh colour
107
Atlantic salmon
ethical concerns/disadv
Possible implication on human health
GMO populations if escaped may affect wild species → deplete populations, harm natural waterways,
Cross breeding of AquAdvantage with wild species decreases biodiversity of wild species → may lead to depletion or extinction
108
Atlantic salmon
Influence of social context
90% of global fisheries are fully exploited, over-exploited or have collapsed
Sciencests have assessed and concluded that GM foods allows on Canadian/US market are safe to consume
New GM foods subject to safety assessment before allows in Canadian/US market
109
Atlantic salmon
Influence of economic context
(4)
Prices fall → benefit for consumers
Food production sector risen in efficiency and production levels offsetting unsustainble capture of shifting practice, contributing to food security
Price might rise → tech and set up costs of these farms, be passed onto consumer causing increased prices
Increased competition → intro of GM salmon on open market might outcompete ordinary salmon farmers → bad for wild salmon market
110
Atlantic salmon
Influence of cultural context
Food safety perceptions, ethical concerns over apporpriate use of animals, environmental concerns effect pubic acceptance of GE fish as food
111
Bt cotton
gene added
Bt gene that comes from the soil bacterium Bacillus thuringiensis
112
Bt cotton
transgenic process
A vector (Agrobacterium tumefaciens bacterium) used to transfer Bt gene from soil bacterium into Bt cotton plant embryos
113
Bt cotton
purpose of modification
The Helicoverpa zea caterpillar (corn earworm) and the Helicoverpa armigera caterpillar (cotton bollworm) feed, damage and destroy cotton plants
Bt gene produces a toxic protein in an inactive form → activates in caterpillar digestive system
Not harmful to humans, animals or insects (most)
114
bt cotton
application
Regular cotton in making clothes, bed linens
115
Bt cotton
adv
reduced need for broad spectrum pesticides
Other beneficial insects (ladybirds, wasps) are not killed indiscriminately
increasing yields and saving farmers money
Reduces risk of resistance to insecticides of the caterpillar population
116
Bt cotton
ethical concerns
Could become resistant to this Bt gene
The gene could be transferred to another species (unlikely)
117
bt cotton
effect on biodiversity
Reduced biodiversity -> leaving changes to ecosystem and reduced the varieties of breeds of plants and animals --> more commercial ones dominate
Insect eating birds population at risk from the use of GM crops with unbuilt insecticides
Natural selection ad evolution of pests that are resistant to widely used pesticides also diminishes the biodiversity as these proliferate at the expense of the varieties susceptible to pesticides
118
Atlantic salmon
Effect on biodiversity
Less need to harvest from wild population
119
bt cotton
influence of social contexts
Dont need pesticides → heightens quality of life through less use of chemicals improving human and ecological health
Allows farmers to meet demands of growing population
Inequality on location and access
Long term health issues: triggering allergies, long term toxicity, changes to nutrition value of food
120
bt cotton
influence of economic contexts
Increase efficiency of farming, industrialization, creasing costs to consumers, increasing profits made by companies
Can reduce poverty in developing countries through growing GMOs that are more efficient and affordable
Save money on pesticides
Higher yield of crop
Consistency of product
121
Bt cotton
influence of cultural contexts
Included to use biotech to maintain significant industries in certain areas e.g. India
“Tampering with nature”
Customs of the area
122
Infectious disease
is caused by another organism or an infective agent known as a pathogen
123
Bacteria
characteristics
● Unicellular prokaryotic organisms
● Cell wall, no membrane bound organelles and nucleus
● Reproduces by binary fission
● Size: 0.2 to 10 µm (larger than viruses, smaller than protozoans)
● DNA: Circular chromosomes & smaller DNA fragments (plasmids)
● Shapes: spherical (coccus), rod-shaped (bacillus), spiral (spirillum), comma-shaped (vibrio)
124
Bacteria
modes of transport
● Parasitic relationship: produces toxins that are harmful to the host’s body
● Transmission: close contacted with another infected host organism, indirectly with an object contaminated with the bacteria
125
Bacteria
Mini case study example
Tetanus
Transmission: Spores enter through broken skin with injuries having been caused by contaminated objects
Features: Fever, sweating, headache, Dysphagia (difficulty swallowing), Tachycardia (rapid heartbeat), Muscle spasms that begin with jaw and spread to rest of body
126
Fungi
characteristics
● Unicellular (yeast) or multicellular (moulds)
○ Hyphae → mycelium
● Eukaryotic organism
● Cell wall composed of chitin
● No chlorophyll
● Heterotropic: feed off other organisms
● Saprophytic: live on dead plant / animal material OR Dermatophytes: Live on skin, nails and hair
● Parasitic: living on a host
127
Fungi
modes of transport
● Cutaneous (outer skin layer), subcutaneous (beneath skin surface), systemic (affecting internal organs)
● May be transferred via close contact with a diseased person or animal, or with contaminated objects.
● In plants, fungi are one of the leading causes of infectious diseases, such as blights, mildews and rusts.
128
Fungi
case study example
Oral Thrush
Transmission: long-term use of asthma inhalers containing corticosteroids and the long-term or use of antibiotics.
Features: lesions on mouth and cheeks
129
Protozoa
characteristics
● Live in the human gastrointestinal tract and are possible sewage and pool contaminants.
● Microscopic, animal-like, unicellular organisms
● Single-celled
● Eukaryotic
● No cell wall
● Binary fission
● Size: 1-30µm
● membrane-bound nucleus, membrane-bound organelles and a cell membrane,
● Cannot grow on nutrient agar (need different parts of the host)
130
Protozoa
Modes of transmission
Vector transmission (i.e. insect bites projecting pathogen into host organism) → Malaria Transmitted via contaminated water → Amoebic dysentery
131
Protozoa
Case study example
Plasmodium (Vector transmission)
Name of disease: Malaria
Symptoms: High fever, Vomiting, Chills, Abundant sweating
132
Cellular/living pathogens
Bacteria
Fungi
Protozoa
133
Non cellular/non living pathogens
Viruses
Prions
134
Macroscopic pathogens
Ectoparasities
Endoparasities
135
Viruses
Characterisitcs
● Size: 30-300nm
● Electron microscope needed
○ Protein coats possess surface proteins that enable it to to attach to host cells via complementary binding
● Contain RNA: Retrovirus
● Types: Icosahedral (Cold virus), spherical virion (Mumps), helical, complex (Bacteriophage)
● Cannot grow on nutrient agar (need cell to replicate)
136
How a virus reproduces
Reproduction → can only reproduce/metabolise IN a host cell
○ Attaches to host cell → Penetration: replicate DNA → Biosynthesis: uses mRNA to make virus proteins → Assembly → Release into body
137
Viruses
Modes of transmission
* Airborne (particles or droplets)
* Contact (smear, hands)
* Contamination (water, food)
* Blood and tissue or bodily secretions (directly like sexual transmission or indirectly like needles)
138
Virus
Case study/example
Name of Virus: Influenza Type A Virus
Name of disease: Influenza A
Symptom:
- Sore throat
- Fever
- Headache
- Fatigue
Mode of Transmission:
- Air transmission via water droplets from sneezing or coughing.
- Inhalation or oral ingestion after unknowingly touching the virus (e.g. park bench).
139
Prions
characterisitcs
● Do not contain genetic material
● cause disease by inducing abnormal folding patterns in the normal proteins that they come in contact with
● Diseases caused known as transmissible spongiform encephalopathies → brain tissue is full of holes
● Cannot grow on nutrient agar (need cell to replicate)
140
What is a prion
an abnormal proteins that is capable of causing degenerative diseases of the nervous system
141
Prions
Mode of transmission
● ingesting or contecting tissue or bodily parts containing infectious prions, such as nervous and brain tissue
● inheriting the mutated gene that codes for the infectious prion
spontaneous formation of infectious prions.
142
Prions
Case study/example
Example of Prion: Prion protein PrPSc
Example of Disease: Creutzfeldt-Jakob Disease
Symptoms of Disease:
● Memory Loss
● Impaired thinking
● Difficulty walking
● Difficult speaking
● Blurred vision
● Depression
Random, involuntary twitches around different parts of body
143
Ectoparasites
Characterisitcs
● Live outside the body, usually sucking blood
● Inject toxins while feeding → inflammation, allergic reactions, partial paralysis
● Vectors for other pathogens → i.e. flea vector for the disease which causes bubonic plague
144
Ectoparasities
Modes of transmission
fleas, ticks, mites, flies, mosquito
145
Ecoparasites
Examples for each vector
Fleas: Bubonic plague
Ticks: Lyme disease → joint pain, rash, fatigue
Mites: Scabies → Red skin, hair loss, itching
Flies: Fly strike in sheep → eggs hatch and maggots burrow and feed off of sheep flesh
Mosquitoes: Zika virus, malaria, dengue fever
146
Endoparasities
Characteristics
● Live inside host’s body
● Commonly inhabit gastrointestinal systems of humans/animals, living on nutrients supplied by host
147
Endoparasities
Modes of transmission
● Nematodes (roundwords, whipworms, hookworms)
● Cestodes (tapeworms)
● Flatworms
148
Endoparasities
Example/case study
Heartworms in dogs: long, thin worms that live in the right side of the heart as adults and block the flow of blood → damage to blood vessels and valves
Symptoms: cough, excess fluid in lungs and abdomen
Transmission: spread by mosquito that bit an infected host and transmit to other dogs
149
Epidemic
a widespread occurrence of an infectious disease in a community at a particular time.
150
Factors must be present for disease to occur:
1. Pathogen- capable of causing the disease
2. Susceptible host- an organism that is free of infection and has not been vaccinated
3. Mode of transmission - way for the pathogen to get from host to host
151
Direct transmission
with example
- Touching, sexual contact, direct contact w/ blood or other bodily fluids, direct contact w/ wounds
- Vertical transmission: transplacental, during vaginal birth, breastfeeding
Examples:
- HIV/AID (via sexual activitty)
152
Indrect transmision
With example
- Contaminated food or water
- Contact with infected surface (fomite)
- Airborne transmission → coughing or sneezing
- Improper sterilisation of surgical equipment
Examples:
Measles virus → from infected droplets
gastroenteritis , caused by E. coli → contaminated food/water
153
Koch's postulates
general/experiment
● Koch’ proved that Anthrax is caused by the bacterium Bacillus anthracis
○ And that tuberculosis is caused by the Mycobacterium tuberculosis pathogen
● Isolated anthrax bacteria from infected livestock
● Koch cultured that bacteria, inoculated into mice, died, mice tissue had anthrax bacteria
● Experimental control: took a sample from an unaffected mice
154
Koch's postulates
Theories
1. The same organism (bacteria/pathogen) must be present in every diseased host, but not in healthy hosts.
2. The pathogen must be isolated and cultured (purely cultured on agar plate) in the laboratory and accurately described and recorded.
3. When a sample of the pure culture is injected/inoculated into a healthy host, this host must develop the same symptoms as the original host.
4. The micro-organism must be able to be isolated from the second host and cultured and identified as the same as the original species.
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Pasteur on microbial contamination
general
● ‘Swan-necked flask’ experiment to disprove spontaneous generation
● Pasteur’s work contributed to the development of vaccines for diseases such as fowl cholera, based on the principle of immunity.
● Pasteur identified microbes as the agents responsible for spoilage during the production of wine, beer and vinegar, leading to the development of pasteurisation
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Pasteur's swan beck flask experiment
Nutrient broth boiled (to kill any microorganisms in broth) in flasks then cooled and air drawn from outside
○ Microorganisms from air did not reach broth as trapped in narrow neck and curve of glass
■ No bacterial/fungal growth observed
○ Bacterial growth in broken flask → exposed to the air and microrganisms in it
○ Tipping flask to allow solution to curve → resulted in bacterial growth
○ Prove that pathogens are airborne and not spontaneous
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Risks from microbial experiment on water and food samples
Burn from bunsen burner, microbiology loop, methylated spirits igniting, infection from cultures
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Pasteurs development of vaccines
○ Using antiseptics in hospitals
○ Attenuated vaccine (weaken pathogens) for anthrax, chicken cholera, rabies
○ Fermentation caused by living yeasts, creating alcohol
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Pasteurs development of pasteurisation
○ Heating wine, beer (and milk) to 72C for 15 seconds kills bacteria
○ Boiling would kill bacteria, but damage taste
○ Reduced incidence of food born diseases (salmonella)
