Download THE SEARCH FOR BETTER HEALTH

THE SEARCH FOR BETTER HEALTH
(Last updated 5th May 2011 by SR/IR)
Contextual Outline
When physiological processes malfunction, the body tries to repair the damage. The process is similar in all
living things and it is only when the process fails to contain the damage that disease can be recognised.
Humans have long recognised the symptoms of disease both in themselves and the animals and plants around
them. Since the beginnings of recorded history, they have noted the signs that reveal that the body is
malfunctioning. Increasing understanding of the causes of disease together with accompanying advances in
technology have changed approaches to treatment and management of disease.
The search for measures to treat and manage diseases of humans and other organisms continues and this
search is paralleled by continued refinements in technology.
This module increases students’ understanding of the history, nature and practice of biology, the applications
and uses of biology, and the implications of biology for society and the environment.
Discuss the difficulties of defining the terms ‘health’ and ‘disease.’
Things to consider:
- What does discuss mean?
- Underline key words
- Be succinct
Defining the term health is not easy as there are many components which fall under health and some of these
components are very subjective. According to the World Health Organisation, (WHO) “health is a state of
complete physical, mental, and social well – being and not merely the absence of disease or infirmity.” This
basically means that good health revolves around a biological, psychological and social well – being.
Biological health: being active and free from pain.
Psychological health: feeling happy, not depressed.
Social well – being: interrelating within the community.
Each of the above factors would all have slight different meanings to different people making the term health
harder to define.
Disease is also another word which is hard to define. Disease as a definition is a state of impaired functioning
by interfering with the structure of organs, tissues or cells or by altering normal metabolism. This definition is
subjective to the functioning of each individual. Meaning that one person may feel that they are sick while
another person with the same symptoms does not feel sick.
Outline how the function of genes, mitosis, cell differentiation and specialisation assist in the maintenance of
health.
Things to consider:
- What does outline mean?
- Underline key words
- Ensure you write about each of the key components that assist in the maintenance of health.
The function of genes, mitosis, cell differentiation and specialisation all assist in the maintenance of health.
They are outlined as follows:
Genes:
Genes assist in the maintenance of health by ensuring that the correct proteins are produced in a cell. This
enables all other cellular processes to continue and to maintain health within the organism.
Mitosis:
Mitosis assists in the maintenance of health by ensuring that genetic material is copied accurately when new
cells are formed. These new genetically correct cells enable the organism to grow as well as repair any
damaged cells or tissue. This therefore maintains health for the organism.
Cell differentiation/specialisation:
During the development of a cell the cell differentiates and becomes a specialised cell for a specific function.
Genes release certain proteins which enable the cell to have a specialised function. Cell differentiation and
specialisation is important in the maintenance of health as these cells enable the organism to grow as well as
repair damaged cells or tissues. Cells may become specialised to fight of infection such as macrophages.
Use available evidence to analyse the links between gene expression and maintenance and repair of body
tissues.
Things to consider:
- What does analyse mean?
- What is gene expression?
- Underline key words and understand what the question is asking before you answer.
- Draw a link between gene expression and repair of body tissue.
Gene expression: is the entire process that takes the information contained in genes on DNA and turns that
information into proteins. (The process of transcription and translation.)
To maintain a healthy lifestyle the appropriate genes during mitosis must be expressed. If there is damage or
no damage to cells or tissue it is still necessary for the appropriate genes to be expressed efficiently in order
for necessary compounds to be produced and therefore a healthy existence.
Example:
During mitosis cells differentiate to have a specialised function. For example in order for muscles to contract
they need the proteins called actin and myosin. The gene responsible for these proteins is “switched on.” The
cell differentiates and becomes a specialised muscle cell. This relates to gene expression and the repair of
body tissue in the sense that the gene responsible for the expression of actin and myosin was triggered. This
resulted in the development of a specialised muscle cell, which in turn repaired the muscle tissue.
Distinguish between infectious and non – infectious disease.
Things to consider:
- What does distinguish mean?
- What are infectious and non – infectious diseases?
- Be succinct
Health and Disease
HSC Core unit 3 The Search for Better Health (Supplementary notes compiled by IR 1/5/11)
Health = state of physical, mental and social well-being
Disease
= any condition that impairs the normal functioning of an organism
Causes of Disease:
1) Infection by parasitic pathogens (or infective particles)
a) Microorganisms such as viruses, bacteria, fungi, protozoans or (prions, a proteinaceous infective
particle).
b) Macro organisms such as:
i) endoparasites (flukes, tapeworms, round worms)
ii) ectoparasites (lice, fleas, mosquitoes, ticks, mites).
2) Heredity
-Chromosomal abnormalities, gene abnormalities, genetic diseases inherited on
autosomes or sex chromosomes.
3) Nutrition
-malnutrition, vitamin deficiencies, mineral deficiency, excessive or insufficient
intake of food (obesity, anorexia, bulimia)
4) Physiological malfunction

Congenital defect form birth, hormonal, nutritional imbalance, cardiovascular
disease, toxic carcinogens (cancer), pollutants & drugs, degenerative ageing, physical
damage from impacts or burns.
5) Environment
a) Pre-natal environment
i) Foetal abnormalities due to rubella in the mother
ii) Foetal alcohol syndrome
iii) Foetal heroin addiction
b) Post-natal environment
i) Stress related diseases (anxiety, hypertension, asthma, diabetes, gastrointestinal ulcers
etc)
ii) Sun damage (skin cancers, cataracts)
iii) Noise damage (deafness)
6) Chemicals
a) Heavy metal poisoning (mercury, lead etc)
b) Drug abuse (tranquillizers, sedatives, narcotics such as morphine & heroin; stimulants such as
caffeine, nicotine, amphetamines & cocaine; hallucinogens such as LSD etc; solvents and
inhalants such as aerosols, petrol, glues).
Non Infectious Diseases:
are caused by some factor other than a pathogen
Infectious Diseases:
are caused by pathogens which invade the body then grow and multiply in the
tissues
Student worksheet
Health
= ........................................................................................................................................
Disease
= ........................................................................................................................................
Causes of Disease:
1) Infection by
2) Heredity such as:
3) __________________ such as:
4) Physiological malfunction such as:
5) Environment
a) Pre-natal environment
b)
Post-natal environment
2) Chemicals such as:
Non Infectious Diseases:
are caused by some factor other than a ..............................................
Infectious Diseases:
are caused by ................................. which invade the body then grow and multiply in the
tissues



INFECTIOUS
Infectious diseases are caused by an infecting
organism which usually invades the body.
Infecting organisms can microscopic or
macroscopic.
A pathogen is an example of an infectious
organism. They include; prions, viruses,
bacteria, protozoans and fungi.


NON - INFECTIOUS
Non – infectious diseases are not caused by a
pathogen and cannot be passed on from
person to person.
Non – infectious disease are usually the cause
of genetic inheritance, nutritional deficiency
and environmental factors. Examples include
Down syndrome (genetic), anorexia
(nutritional) and skin cancer (environmental).
Explain why cleanliness in food, water and personal hygiene practices assist in control of disease.
Things to consider:
- What does explain mean?
- Underline key words.
- Understand the question before answering
It is important that food, water and personal hygiene practices are maintained in order to assist in control of
disease. Food is easily contaminated by visible applications such as dirt or insects or microscopic by micro –
organisms such as salmonella. Hygienic handling of this food controls the spread of disease. Hygienic practices
include; using clean utensils, not sneezing/coughing over food, not using food that has fallen on the floor,
washing hands after being to the toilet, covering cuts and abrasions before preparing food and always placing
perishable foods in the fridge/freezer. If these general hygienic practices were not followed populations could
suffer from food poisoning and disease. It is these simple practices that control disease. Water is easily
contaminated by pathogens such as Giardia and cryptosporidium. These pathogens are controlled by Sydney
Water by constant water testing as well as being filtered and chlorinated before reaching the household.
Sewage is also disposed of in a safe manner in order to control the spread of disease. Personal hygiene refers
to the nature of keeping oneself clean. This includes washing hands after using the toilet, washing hands
before preparing food, showering regularly and washing hands after you have been in contact with something
dirty or a sick person. If this personal hygiene was not kept in order people would easily contract disease from
infectious pathogens. Therefore it is important to maintain cleanliness in food, water and personal hygiene to
assist in the control of disease.
Identify the conditions under which an organism is described as a pathogen.
Things to consider:
- What does identify mean?
- What is a pathogen?
An organism that causes disease is known as a pathogen. For the pathogen to cause disease it must have the
right conditions in order to multiply and transmit itself from organism to organism.
Pathogens can come in the form of prions, viruses, bacteria, protozoans, fungi and parasites. These pathogens
can either be microscopic or macroscopic, meaning they can be seen by the naked eye.
Pathogens can be transmitted in the following ways:
- Air
- Water
- Food
- Direct contact
- Vectors
Identify data sources, plan and choose equipment or resources to perform a first – hand investigation to
identify microbes in food or in water.
Things to consider:
- What does identify, plan and choose mean?
- What are microbes?
- Ensure you plan your own investigation as it is a HSC requirement
Background:
Microbe – an organism which is too small to be seen by the naked eye.
Streaking: Streaking is the technique whereby you use the inoculation loop to streak an agar plate. Firstly the
inoculation loop is placed in the blue flame of the Bunsen burner to sterilise the inoculation loop. (Kill off any
pathogens) The inoculation loop is then swabbed across an area you are wishing to test, for example a piece of
food or a water sample. Then you open the agar plate at a 45 degree angle and swap in a zig zag pattern in the
middle of the agar. See p. 246 to 248.
AIM:
To identify a variety of microbes in food and water.
MATERIALS:
 Sterile agar plates
 Inoculation loops
 Various water samples
 Incubator
 Bunsen Burner
 Food samples
METHOD:
1. Collect a number of agar plates and place them under various conditions. For example in the science
lab, near a rubbish bin or outside on the school oval. Expose each plate for the same amount of time.
Keep one plate closed as a control plate.
2. Collect your plates close them and seal them with sticky tape. Once closed ensure you label your plates
with your name, date and area of exposure.
3. Collect a number of agar plates to test the various water and food samples. Using the streaking
technique collect a sample from the food and water sample and streak your various agar plates. Close
your plate and label with your name, date and food/water you exposed your plate to.
4. Invert your plates and incubate for 24 hours.
5. Once incubated observe your agar plates for bacterial colonies. Colonies can be distinguished through
their characteristics such as colour and texture. Count the number of colonies and record your
observations in the results table.
RESULTS:
NO. OF
COLONIES
LOCATION
COLOUR
TEXTURE
BRIEF DRAWING
Gather, process and analyse information from secondary sources to describe ways in which drinking water can
be treated and use available evidence to explain how these methods reduce the risk of infection from
pathogens.
Things to consider:
- What does gather, process and analyse mean?
- What does explain mean?
- Underline key words
- Understand what the question is asking before answering.
Water is treated to remove impurities and microbes from causing disease to the general public. To prevent the
spread of disease water companies take the following steps to prevent the spread of disease:
- Coagulation and sedimentation
- Filtration
- Disinfection
Coagulation involves adding certain chemicals to the treated water such as alum. The coagulating material
causes dirt, plant debris and other organic matter to clump together and form what is known as a floc. As the
water flows through the tanks the floc settles to the bottom and is removed.
Filters are used to remove small particles such as viruses and protozoans, for example Giardia. Filters are
usually comprised of a specialised membrane, a sand pebble mixture or activated carbon.
The final step is to disinfect the water. Chlorine is the common chemical used in the disinfection stage. Ozone
and U.V. radiation can also be used. Fluoride in some countries may be used to prevent tooth decay. Once
disinfected, water is piped to homes and businesses.
These are the main methods to reduce the risk of infections from drinking water. Not only are these steps
followed but Sydney Water also incorporates strict controls on N.S.W drinking water. These include; fences
around major dams to prevent contamination from animals, adequate distance from farming communities
and distance from sewerage systems. These steps all prevent infection from pathogens.
Describe the contribution of Pasteur and Koch to our understanding of infectious diseases.
Things to consider:
- What does describe mean?
- Who are Pasteur and Koch?
- Ensure you understand their work as scientists are regularly referred to in the HSC.
Louis Pasteur and Robert Koch played a pivotal role to our understanding of infectious diseases. Louis Pasteur
a French chemist discovered that most infectious diseases are caused by micro – organisms, or germs. This
became known as Germ Theory. Through Pasteur’s research on fermentation he was able to identify and
describe the micro – organisms that cause fermentation. During this research Pasteur also disproved the
theory of spontaneous generation.
Due to Pasteur’s knowledge of microbes and fermentation he was involved in many industries including the
wine industry. Pasteur showed that microbes, which caused wine to spoil, could be killed by heating the wine
to 55oC. This process was also applied to milk and beer and is now known as pasteurisation.
Pasteur also demonstrated that anthrax a disease that affected cattle, sheep and horses was caused by a
bacterium known as Bacillus anthracis. He developed a technique by weakening a strain of this bacterium and
injecting it into certain animals. On one occasion he took 50 sheep and injected 25 of them with the weakened
disease. Several days later he injected all 50 of the sheep with a strong dose of the disease. Pasteur predicted
that 25 of the sheep would die. Subsequently 25 sheep did die and 25 survived. Today this process is
commonly known as vaccination. Pasteur developed many vaccines including vaccines for anthrax, chicken
cholera and swine erysipelas.
Robert Koch was also heavily involved in microbial work, in particular anthrax. Koch was successful in isolating
the bacterium from the blood of dying animals. He examined the blood under the microscope and identified
active rod – shaped cells and resting spores. He concluded that all infected organisms contained these
microbes, while healthy organisms did not. Koch also found that if blood taken from an infected organism was
injected into another organism it would contract the disease. To prove that it was not another component of
the blood Koch extracted the bacteria only and injected it into a healthy organism, subsequently causing the
disease. From this research Koch provided step by step guidelines to prove that a particular micro – organism
causes a particular disease. These are known as Koch’s postulates and are as follows:
1. The specific micro – organism must be present in all infected organisms.
2. The specific micro – organism must be isolated from the host and grown in a pure culture.
3. A healthy organism is then injected with the micro – organism. This organism must develop the same
symptoms as previous infected organisms.
4. The specific micro – organism must be isolated from the second host and be the same species of micro
– organism as the one originally injected.
It was through the work of Pasteur and Koch, which laid the foundations for scientists to study micro –
organisms. This has led to a greater understanding of infection control and hygienic practices.
Perform an investigation to model Pasteur’s experiment to identify the role of microbes in decay.
Things to consider:
- What does perform mean?
- What does identify mean?
Refer to page 260 to 261. “Modelling Pasteur’s experiment.”
Distinguish between:
- Prions
- Viruses
- Bacteria
- Protozoans
- Fungi
- Macro – parasites
And name one example of a disease caused by each type of pathogen.
Health and Disease
HSC Core unit 3 The Search for Better Health (Supplementary notes compiled by IR 1/5/11)
General Features of Pathogenic Organisms
Viruses
 0.01 – 0.3µm in size
 Lack cell membrane & cell structure
 3 types (animal viruses, plant viruses, bacterial viruses (bacteriophages))
 Outer protein coat containing nucleic acid, varying structure (see p9 Sakker et al, 1998)
 2 phase life cycle
o Exracellular phase – exists as inert infective particle
o Intracellular phase – replicates DNA or RNA in host
 (see Fig 7.10 & 7.11 p. 355 BIF)
Fungi
 3.0 - 10µm diameter
 Can be unicellular e.g. yeasts or
 Multicellular such as moulds, mushrooms
o Filamentous
o Branching filamentous (hyphae, mycelium)
o Hyphae septate (cross walls) in most species. Cells may be uninucleate or multinucleate
 Most fungi produce spores either in sporangium (see p357 BIF) or at tips of hyphae.
 Cell wall usually of chitin (some have cellulose)
 Heterotrophic (no chlorophyll), excrete enzymes to digest substrate externally before absorption.
 No roots, stems, leaves or vascular systems
 Reproduce asexually, sexually or both
 Tolerate 0 – 300C+, pH 2 – 9
 Tinea Fig 7.6 p. 345 BIF, Ringworm Fig 7.15 p359 BIF
Bacteria
 Procaryotic
 0.5 – 5.0µm size
 Most are free living, many are commensalistic (living in or on organisms), and some are parasites.
 Varying shapes but all have same basic internal structure (no membrane bound organelles, no true
nucleus, cell membrane, cell wall, single strand DNA (nucleoid), ribosomes, enzymes, cytoplasm)
 Some have capsule (slimy covering layer around cell), flagella, pili, spores (see Fig 3.12 p. 266 BIF)
 Classified according to:
o Staining ability (gram positive or gram negative)
o Shape (see figure 3.13 p266 BIF)
 Spheres
 Cocci
(a single cell)
 Diplococcic (pairs of cells)
 Streptococci (chains of cells
 Staphlococci (clusters of cocci)
 Tetrads
(groups of four)

 Sarcinae
(packets of 8)
 Rods called bacilli
 Curves called spirilla
 Comma shaped called vibrios
Reproduce asexually by binary fission, can multiply as short as every 10 minutes i.e. in 24 hours (1440
minutes) one bacteria can multiply (2144) to 2.230072 X 1043 in number!
Protozoa
 Unicellular
 Mostly microscopic 2.0 - 1000µm size
 Cell membrane
 No cell wall
 Mostly heterotrophic
 Classified on basis of locomotion (see figure 3.15 p267 & figure 3.16 p268 BIF)
o Flagellates
e.g. Trypanosoma (African sleeping sickness)
o Ciliates e.g. Paramecium
o Amoeboids e.g. Amoeba such as amoebic dysentry
o Sporozoans non-motile e.g. Plasmodium malaria, cryptosporidium
 Reproduce asexually, sexually or both
 Require moist habitat
 May be:
o Free living (no host)
o Commensalistic (one benefits, host unharmed)
o Mutualistic (both benefit)
o Parasitic (one benefits at the expense of the other)
Prions
 Infective agents that cause brain disease and death in mammals e.g. mad cow disease, CreutzfeldtJacob disease (CJD) in humans, scrapie in sheep.
 Diseases caused by prions are called spongiform diseases because the brain tissue becomes full of
holes like a sponge.
 Are proteins that have been altered from their normal shape, but are chemically the same.
 A prion can convert other similar but normal proteins into abnormal prion shape (fig 3.8 p263 BIF)
 Can be passed from one animal to another i.e. are infective.
Rickettsias (not in syllabus)
 Smaller than bacteria 0.2 – 1.0µm long but classified into a different group because they cannot survive
outside living cells
 Procaryotic, gram negative, non-motile, non spore forming type of bacteria
 Oval-shaped
 Intracellular parasites
 Have cell walls
 Cannot grow outside of living cells
 Transmitted by arthropods (fleas, ticks, lice)
Mycoplasmas (not in syllabus)
 Smallest cellular creatures ever discovered, 0.1 – 0.2 µm diameter
 Have only half the amount of DNA of other prokaryotes
 Are intracellular parasites of animals and plants
 A genus of bacteria that lack cell walls thus shapes can be irregular


Cannot be killed with Penicillin as they do not have a peptidoglycan cell wall (Penicillin kills bacteria by
interfering with wall synthesis)
Can cause atypical pneumonia and respiratory disease in humans
Student Worksheet
Summary of some features if microorganisms
Microbe
Size
Structure
Method of
Reproduction Transmission Comment
(µm)
classification
examples
Virus
Bacteria
Protozoa
Fungi
Prion
TYPE OF
PATHOGEN
Prions
DESCRIPTION
EXAMPLE(S)
A prion is a special type of protein that causes
the degeneration of brain tissue.
Scrapie in sheep. Bovine
spongiform encephalitis (mad cow
disease) and Creutzfeldt – Jakob
disease.
Viruses
Viruses are many times smaller then the smallest
bacterial cell. They are borderline between living
and non – living. This is due to a lack of
metabolism and life characteristics. Viruses rely
on the hosts individual cells and nucleic acids to
produce more of the same virus.
AIDS, chicken pox, genital herpes,
cold sores, measles, rubella,
glandular fever, hepatitis and
influenza.
Bacteria
Bacteria are disease – causing to the host as they
multiply rapidly in blood and tissues. Bacteria
also produce toxins which are harmful to the
host’s body. Bacteria reproduce by binary fission
which can take as little as 10 minutes to as long
as 24 hours.
Pneumonia, Cholera, legionnaire’s
disease, diphtheria and tetanus.
Protozoans
Protozoan’s are classified by the way they move. African sleeping sickness, Malaria,
For example flagellates move by using a whip like Amoebic dysentery and giardiasis.
structure called flagellum. Ciliates move by using
tiny hairs called cilia, pseudopods use feet like
structures which are extensions of the cytoplasm
and sporozoa have no structures for motion.
Protozoa are mainly found in water.
Fungi
Fungi can either be caused by saprophytes, the
fungi you find on dead plant or animal tissue or
parasitic fungi such as athlete’s foot. (Causes
flaky, itchy dry skin.)
Candidiasis (thrush), athlete’s foot.
Macro parasites
Macro - parasites can either be external
parasites (ectoparasites) or internal parasites
(endoparasites).
Fascioliasis, Schistosomiasis,
hydatid disease, taeniasis,
enterobiasis, scabies, house dust
(mites).
Some common diseases caused by microorganisms
Viruses
Influenza
Common cold
Cold sores
Genital herpes
Chicken pox
Shingles
Small pox (eradicated)
German measles (rubella)
Measles
Mumps
Glandular fever
Hepatitis A, B, C
Poliomyelitis
Ross river fever
Encephalitis
Viral meningitis
Viral conjunctivitis
Warts
Yellow fever
AIDs
Domestic animals
Foot & mouth disease
Blue tongue
Rinderpest
Distemper
Rabies
Bacteria
Diphtheria
Whooping cough
Tetanus
Tuberculosis (TB)
Syphilis
Gonorrhoea
Cholera
Legionnaires disease
Salmonella (food pois.)
Botulism (food pois.)
Gas gangrene
Gastroenteritis
Rheumatic fever
Scarlet fever
Typhoid fever
Bacterial meningitis
Bacterial conjunctivitis
Golden staph (food pois)
Bubonic plague (bacillis)
Brucellosis
Dysentery (bacterial)
Pneumonia (bacterial)
Erysipelas
Impetigo
Leprosy
Campylobacter
Shigella
Yaws
Yersinia
Tonsillitis
Anthrax
Fungi
Tinea
Candidiases (Thrush)
Ringworm
Dandruff
Prions
Mad cow disease,
Creutzfeldt-Jacob
disease (CJD) in
humans
Scrapie in sheep.
Protozoa
Malaria
African sleeping sickness
Amoebic dysentery
Chagas disease
Giardia (flagellate
diarrhoea)
Cryptosporidium
Cyclospora
Leishmaniasis
Toxoplasmosis
Rickettsias &
mycoplasmas
Trachoma
Venereal disease
Forms of pneumonia
Typhus
Table 1: Diseases caused by viruses
Viral
Diseases
AIDS
(acquired
immune
deficiency
syndrome)
chicken
pox
cold sores
genital
herpes
measles
rubella
(German
measles)
Cause
HIV
(human
immune
deficiency
virus)
herpes
varicellazoster
virus
herpes
simplex
type 1
virus
herpes
simplex
type 2
virus
morbilli
virus
rubella
virus
Transmission
by direct contact of
body fluids, e.g.
through sexual
contact or blood
transfusion or dirty
needles used by drug
addicts
air; skin contact; the
placenta via the
foetus; indirect
contact (bedding etc.)
direct skin contact;
indirect contact
through bed linen,
towels etc.
direct contact during
sexual intercourse or
at birth
in air droplets
glandular
fever
EpsteinBarr virus
direct contact
(touching); indirect
contact (for example,
bedding); in air
(coughing, sneezing);
via placenta to foetus
direct contact
including saliva
infective
hepatitis
(hepatitis
A)
hepatitis A
virus
contaminated food or
water
hepatitis B
hepatitis B
virus
influenza
influenza
virus —
there is a
family of
these
viruses
sexual intercourse;
contaminated
injection needles
in air from sneezing,
coughing or breathing
Symptoms
fatigue, loss of
appetite and weight;
diarrhoea; infections
and other diseases
such as Kaposi’s
sarcoma (a skin
cancer)
pink spots that
become itchy, blister
and burst
Treatment and control
treatment AZT and other drugs (not
curative)
control change of lifestyle among
promiscuous individuals and drug
addicts
fatigue; headaches;
limb pains
treatment no drugs available; adequate
rest for patient control isolation of
patients
treatment no drugs available; adequate
rest for patient control isolate patient;
vaccine
treatment antibodies are produced to
confer natural immunity, calamine
lotion reduces the itchiness
control isolation of the patient
sores on mouth or lips treatment use of mouth-washes;
that form blisters
ointments (anti-viral) control avoidance
of direct contact during attacks, vaccine
(a recent development)
sores on the genital
treatment the drug acyclovir will reduce
area
the severity of attacks
control avoidance, e.g. sexual contact
during attacks; good diet and rest;
vaccine (recently developed)
rash on body; nausea; treatment no drugs available; adequate
headache; fever
rest for patient control vaccination
sore throat; fever;
treatment fluids, analgesics, to relieve
headache; rash (rash
or reduce pain
less severe than
control isolation of patients;
measles)
immunisation especially of teenage girls
fever alternated with
shivering; pains in
limbs; jaundice
(yellowing of skin);
fatigue; headache
nausea; fatigue;
jaundice
headache; pain in
limbs; respiratory
tract infection; fever
treatment no drugs available control
clean injection needles; screen blood
donors; vaccine
treatment rest; analgesics control
precautions by infected people when
sneezing and coughing; vaccines are
effective against some strains
Table 2: Diseases caused by bacteria
Disease
Cause
pneumonia
Diplococcus
pneumoniae; or
Streptococcus lung
congestion
pneumoniae (bacteria)
Transmission
in air from
sneezing and
coughing
Symptoms
f ever; coughing
lung congestion
Treatment and control
treatment penicillin and other
antibiotics
control isolation of patients
cholera
Vibrio cholera
(bacterium)
in water
contaminated
with sewage; in
contaminated
food
severe diarrhoea
and dehydration
treatment replacement of water
and salts; drugs such as tetracycline
and
chloramphenicol
control purification of water; food;
good
sewerage system; vaccination
legionnaires’
disease
Legionella
Through airconditioning
systems
Fever, coughing
lung congestion
Treatment antibiotics rifampicin and
erythromycin
Control regular sterilisation of airconditioning systems; isolation of
patients
diphtheria
Corynebacterium
diptheriae
Direct or
indirect contact
Spots on throat
and tonsils;
headache;
vomiting
Treatment: drugs and antibiotics
Control: isolation of patients;
immunisation especially of children
Table 3: Diseases caused by protozoans
Disease
Cause
African
Trypanosoma species
sleeping
(protozoan)
sickness
malaria
Plasmodium species
(protozoan)
amoebic
dysentery
Entamoeba histolytica
(protozoan)
giardiasis
Giardia lamblia
(protozoan)
Transmission
intermediate
host is the
tsetse fly which
transfers the
pathogen to
blood when it
bites humans
by the vector
the Anopheles
mosquito
Symptoms
fever, headache;
enlarged lymph
glands;
drowsiness; coma
Treatment and control
treatment drugs control eradicate
tsetse fly; protection of humans
against tsetse flies; early diagnosis
and treatment; perhaps a vaccine
in the future
fever alternating
with shivering;
anaemia
unhygienic food
and water
supplies;
uncooked food
unhygienic food
and water
supplies;
uncooked food
diarrhoea;
nausea; vomiting;
fever
treatment chloroquine and other
drugs control elimination of
mosquitoes’ breeding places—
usually ponds and lakes;
eradication of mosquitoes; use of
preventive drugs in humans;
precautions such as clothing,
mosquito nets
treatment drugs e.g. antibiotics,
including sulfa drugs control
eradication of flies that spread the
disease; hygiene in food handling
treatment anti-protozoan drugs
control hygiene in food handling;
proper treatment of drinking
water
Table 4: Diseases caused by fungi
Disease
Cause
Transmission
candidiasis
yeast (Candida C. albicans occurs
(‘thrush’)
albicans)
naturally in human
tissues; if the
competition from other
natural microbes is
upset it can cause
symptoms; it can be
transmitted from a
vaginal infection in the
mother to the baby at
birth
athletes’ foot fungus (Tinea
direct contact
pedis)
(touching); indirect
contact through use of
towels,
showers, swimming
pools
diarrhoea;
nausea; vomiting;
bloating;
flatulence
Symptoms
white patches in
mouth or
itchiness in the
vaginal area or
inflamed skin
Treatment and control
treatment specific anti-fungal
chemicals
control keeping susceptible areas
of the body clean
and dry; altering whatever causes
the imbalance
e.g. oral contraceptives
itching and
blisters between
toes; skin peels
and cracks;
secondary
bacterial
infections
are possible in
the cracks
treatment anti-fungal chemicals
taken orally or
applied externally
control care in drying between the
toes after bathing;
infected individuals should avoid
sharing towels etc.
Table 5: Some diseases caused by macroscopic parasites
Disease
Cause
Transmission
facioliasis
Fasciola hepatica (liver through plants
(sheep liver
fluke)
or grass in damp
disease)
areas that
contain the
cysts
Symptoms
haemorrhaging of
liver tissue; bile
duct blockage;
abdominal pain;
anaemia
schistosomiasis Schistosoma (blood
(blood fluke
fluke)— there are a
disease,
few different species
sometimes
called
bilharzia)
from water
supplies that
are
contaminated
with the cysts
loss of weight;
diarrhoea;
anaemia;
abdominal pain;
itchy skin and
rash
hydatid
disease
Echinococcus
granulosus
(tapeworm)
by touching
infected dog’s
hair or faeces
and transferring
the eggs to the
mouth
taeniasis
(tapeworm
disease)
Taenia solium (pork
tapeworm) or Taenia
saginata (beef
tapeworm)
by
undercooked,
infected pork or
beef
anaemia;
pressure on
internal organs;
severe pain and
severe shock if
the cysts burst;
death in severe
cases
loss of weight;
possibly
abdominal pain
enterobiasis
(threadworm
disease)
Enterobiasis
vermicularis
(threadworm)
from bed linen
or other items
that contain the
eggs
restlessness at
night; anal
itchiness
scabies
Sarcoptes scabei (itch
mite)
severe itching
house dust
mite asthma
Dermatophagoides
usually by indirect
contact
pteronyssinus—the
through bed linen,
carpets, house dust
mite house dust
by direct skin
contact from
infected people
or indirect
contact through
bed linen
allergic
reaction;
coughing;
sneezing
bronchial
congestion
treatment some
drugs used in
treating allergies
are useful control
regular
vacuuming, airing
bedding; use of
anti-allergen
spray
Treatment and control
treatment the drug bithionol
control eradication of fresh water
snails; proper water and sewerage
systems; clean water troughs for
sheep; care by humans with wet
grass or plants
treatment there are drugs that
are effective if the disease is
diagnosed early
control proper water and
sewerage systems; treatment of
infected people; eradication of
fresh water snails
treatment there are no known
drugs to cure this disease
control worm treatment for dogs;
proper hygiene when handling
dogs; thorough cooking of meat
for dog food; early treatment and
prevention of the disease in cattle
and pigs
treatment the drug miclosamide
control thorough cooking of pork
and beef; early treatment and
prevention in cattle and pigs;
strict abattoir inspection of meat
treatment combantrin (taken
orally); family treatment
recommended
control strict hygiene with bed
linen, towels etc.
treatment external application of
chemical to the skin (family
treatment recommended)
control strict hygiene with bed
linen etc.; early treatment of
infection
Treatment some drugs used in
treating allergies are useful
Control regular vacuuming, airing
bedding; use anti-allergen spray
Identify the role of antibiotics in the management of infectious disease.
Things to consider:
- What does identify mean?
- What are antibiotics and what are their uses?
The chief role of antibiotics is to destroy or inhibit the growth of bacteria. They are special types of chemicals
which act selectively on invading pathogens without affecting the host. They only work on bacterial infections,
not viruses.
Different types of antibiotics target different types of bacteria. ‘Broad - Spectrum,’ antibiotics act on a large
range of bacteria while ‘narrow – spectrum,’ antibiotics act on a small range of bacteria.
Antibiotics work at a cellular level. They interfere with the development of the bacteria by either damaging or
destroying the bacterial cell. For example penicillin has a special ring shaped molecule which gives it
bactericidal properties. This affects the formation of the bacteria’s cell wall.
Gather and process information to trace the historical development of our understanding of the cause and
prevention of malaria.
HISTORY SHOWING THE DEVELOPMENT OF OUR UNDERSTANDING OF MALARIA
Early 19th Century: Cause of malaria unknown. Antimalarial properties found on cinchona tree. (Quinine)
1880: First malaria parasite seen in blood by Charles Laveran.
End of the 19th Century: Connection between mosquito and malaria parasite made by Ronald Ross. Found that
mosquitoes carrying the disease infected volunteers who were bitten by the mosquitoes.
1898: Ross describes the life cycle of the malaria parasite.
The Beginning of the 20th Century: Chemical nature of quinine determined which led to the synthesis of drugs.
Most effective was chloroquin. Continued use of drugs led to resistance in the malarial parasite.
1940’s: Evidence to suggest that people with one gene for sickle – cell anaemia are more resistant to malaria
due to shape of their red – blood cells.
1990’s – 2000: Continued research to produce a vaccine.
LIFECYCLE OF MALARIAL PARASITE
Firstly a female anopheles mosquito bites a human using their feeding tube or stylet. On the stylet are many
sporozoites. These sporozoites make there way into the bloodstream. The sporozoites need to develop. This is
achieved if the sporozoites make it to the liver. Once the sporozoites make it to the liver they are supplied
with nutrients to grow and divide. This is known as asexual reproduction and each sporozoite produces 16
smaller spherical merozoites. They are released into the blood plasma where the merozoites invade red blood
cells. The red blood cells become so full of merozoites that they burst causing waste product to enter the
bloodstream. This causes symptoms such as a fever. Some merozoites develop into female and male
gametocytes. If a mosquito feeds on a human suffering from malaria these gametocytes maybe transferred
into the mosquito. These gametocytes become gametes in gametes in the mosquito, they replicate and
eventually produce sporozoites, and so the cycle continues.
PREVENTION OF MALARIA
 Anti – Malarial drugs administered before visiting endemic areas.
 Prevention aims to keep the disease at a minimum.
 Breeding grounds of the vector maybe destroyed.
 Draining of swamps and using insecticides.
 Development of vaccines.
 Genetic engineering of mosquitoes to develop individuals who will resist the parasite.
These are some of the measures to prevent the spread of malaria.
Process information from secondary sources to discuss problems relating to antibiotic resistance.
Things to consider:
- What does process mean?
- Always refer to antibiotic resistance.
Identify defence barriers to prevent entry of pathogens in humans.
- Skin
- Mucous membranes
- Cilia
- Chemical Barriers
- Other Body Secretions
Things to consider:
- What does identify mean?
- Be succinct; write briefly about each defence barrier.
The body has numerous defence barriers which prevent the entry of pathogens into the body. They are as
follows:
Skin
-
Has a tough coating
Contains chemicals that destroy invading organisms
Certain bacteria on skin destroy incoming pathogens
Dry, pathogens rely on damp areas to grow
Mucous membranes
- Production of mucus carries pathogens out of the body
- Nasal passage traps and secretes pathogens
- Respiratory system produces mucus. Reflex actions such as coughing eject the pathogen from the body
- Urogenital surfaces can produce mucus to excrete any invading pathogens
Cilia
-
Found in the nasal, throat, ear and respiratory system.
Consists of tiny hairs
With the help of mucus trap pathogens and secrete them out of the body
Chemical Barriers
- Stomach acid provides a lethal environment for pathogens
- Saliva and tears contain lysosomes which destroy invading pathogens
Other Body Secretions
- Other body secretions include; bacteria in intestines, wax in ears, urine and sweat. These all prevent
invading pathogens.
Health and Disease
HSC Core unit 3 The Search for Better Health (Supplementary notes compiled by IR 1/5/11)
Pattern of Infectious Disease:
1)
2)
3)
4)
5)
Entry into body
Incubation
Appearance of symptoms
Crisis
Convalescence
- the period from entry of the pathogen until the symptoms appear
- nausea, fever, etc …
- recovery or death
- the symptoms disappear and the patient recovers
Treatment:
 Treat symptoms only, whilst allowing the body to produce its own antibodies to overcome the
infection
 Medicine to attack microorganisms e.g. antibiotics or sulfoamide drugs for bacterial infections
 Aid the body’s natural defence mechanisms by injecting antibodies or antitoxins so as to render
harmless either the pathogen or its toxins, e.g. antitoxin to treat diphtheria.
Control:








Reduce source of infection (isolate, quarantine...)
Reduce transmission of infection (interrupt life cycle of pathogens)
Protect susceptible people (immunisation, vaccinate to help body defences
Education to increase awareness
Provide clean water, clean food and effective sewage treatment
Sterilise or disinfect contaminated articles
Personal hygeine
Screening of possible carriers of disease
Identify antigens as molecules that trigger the immune response.
Things to consider:
- What does identify mean?
- What is an antigen?
- What is an immune response?
An antigen is a molecule that causes an immune response within the body. Antigens are carried on pathogens.
When the pathogen enters the body, the body recognises the antigen and begins to produce an immune
response.
Explain why organ transplants should trigger an immune response.
Things to consider:
- What does explain mean?
- Relate answer to antigens
- What is an immune response?
The body immune response is due to the invasion of foreign material. In organ transplants diseased tissue is
replaced by healthy tissue such as kidney’s, liver, heart, lungs and bone marrow. These healthy tissues are
foreign to the body and contain certain proteins (antigens) that are recognised as foreign. The patient’s body
then stimulates the production of antibodies that attack and possibly destroy the new tissue. To prevent the
rejection of the organ transplant the patient’s immune system is suppressed. This is due to the fact that blood
drains into the recipient’s circulation; the body recognises the foreign tissue cells and produces antibodies in
response.
Rejection is reduced by matching the transplanted tissues proteins as closely as possible with the recipient’s
proteins. Anti – rejection drugs are also administered. These suppress the immune response and prevent
rejection of the organs. e.g. Antilymphocyte Globulin (ALG)
Identify defence adaptation including:
- Inflammation response
- Phagocytosis
- Lymph System
- Cell death to seal of pathogens
Things to consider:
- What does identify mean?
- Consider a suitable method of answering this question such as a table.
DEFENCE
ADAPTATION
DESCRIPTION
Inflammation
response
When body tissue has been invaded by a pathogen, the area of infection may
become hot, red, swollen and painful. The blood circulation to that area is increased
and the blood vessels dilate leaking more blood in the infected area. This response
helps confine the pathogen, while the increase in blood volume leads to an increase
of white blood cells which help destroy the invading pathogen. This process also
allows for the quick removal of dead cells as well as the removal of toxins so that
normal body function can occur. (Histamines and prostaglandins are chemicals which
mediate the inflammation response.)
Phagocytosis
Phagocytes are a special type of white blood cell which actively moves from the
blood where they ingest and destroy any foreign materials such as pathogens. This is
known as phagocytosis. In acute inflammation which only lasts for a few hours or
days, the main phagocytes used are called neutrophils. In chronic inflammation
which lasts for weeks or months the main phagocyte used are called macrophages.
This defence adaptation allows for the efficient decomposition and destruction of
invading pathogens.
Lymph system
The lymph system is a network similar to that of our own circulatory system. This
system transports a special fluid known as lymph similar to that of extracellular fluid.
Lymph is transported away from the cells towards the heart. At various points
around the body are smaller vessels called lymph nodes. Lymph nodes are
responsible for the production of lymphocytes. These lymphocytes are added to the
lymph as it flows through the body. Lymph nodes are also responsible for engulfing
and destroying bacteria and other foreign material. Lymph nodes become swollen or
inflamed when fighting off infection due to the toxins released by the bacteria.
Lymphocytes are white blood cells the main two types being T cells and B cells.
Cell death to seal Sometimes the body will seal of a group of pathogens to form a cyst. Part of this cyst
of pathogens
will involve a group of cells. These cells are sacrificed so that the pathogen can be
destroyed.
Gather, process and present information from secondary sources to show how a named disease results from an
imbalance of microflora in humans.
Things to consider:
- What do gather, process and present information mean?
- Ensure you used a named disease
- What is microflora?
- Page 282
Microflora in humans are microbes which live in the human body without causing disease. This is a symbiotic
relationship whereby the digested food is processed by the microbe in return for essential vitamins.
An example of a named disease which results in an imbalance of microflora in humans is candidiasis. The
following information outlines how the imbalance of Candida affects a human:
- Candidiasis is the over population of the yeast/fungus Candida albicans.
- This yeast like organism is highly present in our mucous membranes.
- Candida albicans is controlled by lactobacilli and bifidobacteria largely found in the intestinal tract.
- When lactobacilli and bifidobacteria numbers drop there is a sudden increase in the numbers of
Candida in the gastrointestinal tract.
- Candida then changes from a yeast like form to a fungal form. This fungal form has root like structures
which enter the lining of the gastrointestinal tract.
- This weakens the gastrointestinal tract and substances usually confined to the gastrointestinal tract
leak into the bloodstream.
- Partly digested proteins enter the bloodstream which results in the production of antibodies from the
immune system.
- This usually results in severe allergic reactions including cerebral (brain) allergies.
- Rapidly growing populations of Candida can almost relocate anywhere in the body causing numerous
amounts of problems. In children an excess of Candida usually results in the common disease known as
thrush.
It is evident that through a slight imbalance in microflora in humans may result in the emergence of disease.
(http://www.wadsworth.org/databank/hirez/wongp1.gif)
MICROGRAPH OF CANDIDA ALBICANS
Identify the components of the immune response:
- antibodies
- T cells
- B cells
Things to consider:
- What does identify mean?
- Write brief descriptions of the above components of the immune response.
- Page 291
COMPONENTS OF
IMMUNE RESPONSE
ANTIBODIES
DESCRIPTION
Antibodies also known as immunoglobulins are produced in the lymph nodes
by B cells in response to a specific antigen. Antibodies are special proteins
which circulate in the blood plasma and combine with B cells to destroy
antigens. This is called antibody – mediated immunity.
T CELLS
T cells are a type of lymphocyte which form in the bone marrow and mature
in the thymus gland. They remain inactive while travelling around the body
until they come into contact with an antigen. The T cell binds onto the
antigen and makes copies of itself. T cells control the cell – mediated
response whereby various types of T cells destroy the antigen or foreign cell.
B CELLS
B cells develop and mature in the bone marrow. B cells are activated in the
blood when there is a presence of an antigen. Activated B cells clone
themselves into either plasma cells which send antibodies into the blood or
into memory cells.
Describe and explain the immune response in the human body in terms of:
- interaction between B and T lymphocytes
- the mechanisms that allow interaction between B and T lymphocytes
- the range of T lymphocyte types and the difference in their roles
Things to consider:
- What does describe and explain mean?
- Identify the best way to answer this question.
- Understand what you are writing before you write it down.
The immune system and the components within the immune system are constantly interacting with one
another to provide the best defence against invading organisms. One such interaction is the interaction
between B and T lymphocytes (cells). T cells and B cells work together by attacking the same antigen. Helper T
cells, a special type of T cell, stimulate the cloning of T cells and B cells to help destroy invading pathogens. T
cells can also trigger an immune response in B cells by secreting a substance known as a cytokine. This special
protein signals other cells to trigger an immune response. Although B cells and T cells are constantly
interacting there are certain mechanisms in place which prevent these cells from attacking one another. For
example if a B cell is expressing an antigen on its membrane it is not destroyed by another T cell. The body has
adapted a mechanism whereby cells are capable of recognising “self” molecules. This prevents the
unnecessary destruction of the bodies own cells.
There are a range of T cells that all have a specialised function in preventing the spread of disease in the
human body. Cytotoxic T cells destroy cells that contain foreign antigens. These non – self molecules such as
bacteria are destroyed by cytotoxic T cells and are removed from the body. Helper T cells secrete a chemical
known as interleukin which regulates the function of T and B cells. Suppressor T cells regulate the activity of B
and T cells. For example cytotoxic T cells are suppressed once they have carried out their role.
Outline the way in which vaccinations prevent infection.
Things to consider:
- What does outline mean?
- What are vaccinations?
- Be succinct
The process of vaccination also known as immunisation is the process of making people resistant to an
infection caused by a pathogen. Vaccines can be administered in two ways, one via injection the other via an
oral dose. Vaccines are a preparation of a weakened or dead infective micro – organism. This dose is injected
into the patient with the intention of eliciting an immune response to the disease without causing any
symptoms. Some vaccines are only administered once as the patient will have immunity for life, for example
the measles vaccine. Other types of vaccines require a “booster,” vaccine which is administered 5 – 10 years
after the original vaccination. This increases the immunity against the disease, a type of this vaccination is
tetanus. Overall vaccinations prevent disease as they enable our body to register an immune response and
build up memory cells which in turn will fight the disease if the person is ever exposed to that disease.
Outline the reasons for the suppression of the immune response in organ transplant patients.
Things to consider:
- What does outline mean?
- Relate answer to the immune system.
- Understand what the question is asking before you answer.
Suppression of the immune response is a necessity after an organ transplant in order for the new organ not to
be rejected by the recipient. As some blood from the donated organ enters the blood stream of the recipient,
the body recognises the foreign tissue cells and begins to produce antibodies in response. A number of cells
such as cytotoxic T cells are produced which could affect the implanted tissue.
The rejection of this organ is reduced by closely matching the donor organs proteins to the recipient’s
proteins. By doing this it allows the recipient a higher chance of accepting the organ. The immune system is
also suppressed after an organ transplant. Antilymphocyte globulin (ALG) is a drug that suppresses the
immune response. This drug allows the recipient a greater chance of accepting the organ rather then
destroying it.
A balance between suppressive drugs and monitoring increases the chances of the organ transplant being a
success.
Identify and describe the main features of epidemiology using lung cancer as an example.
Things to consider:
- What does identify and describe mean?
- What is epidemiology?
- Be succinct.
Epidemiology is the study of disease that affects many people. These types of studies describe the patterns
and causes of certain diseases within a population. The diseases studied can be infectious diseases such as
influenza and non – infectious diseases mainly caused by lifestyle and environmental factors. Epidemiological
studies have been able to establish links between smoking and lung cancer. With this knowledge government
agencies can take preventative measures such as warnings on smoking packets or advertisements which show
the adverse effects smoking has on the human body. It is through epidemiology scientists have been able to
draw links between disease and certain underlying factors which in turn gives rise to treatment, control and
prevention.
Identify causes of non – infectious disease using an example from each of the following categories:
- inherited disease
- nutritional deficiencies
- environmental diseases
Non – infectious disease is caused by many underlying factors. These factors include the malfunction of the
physiology, metabolism or structures of the body. These malfunctions lead to the deprivation and disease for
the human body. Non – infectious disease falls into three main categories. Firstly inherited disease is a non –
infectious disease passed on from generation to generation through the genetic code of the family. An
example of an inherited disease is Down syndrome. Secondly nutritional deficiencies cause non – infectious
disease by either malnutrition (nutrients totally unbalanced) or under - nutrition (not enough food). Some
examples of nutritional deficiencies include anorexia nervosa, kwashiorkor and Aboriginal nutritional diseases.
Thirdly environmental factors cause non – infectious disease by polluting the body with unnecessary and often
poisonous substances. Such substances include alcohol, tobacco, drugs and heavy metals. These poisons can
cause disease such as heavy metal poisoning, cirrhosis of the liver or lung cancer.
Gather, process and analyse information to identify the cause and effect relationship of smoking and lung
cancer.
Ever since the introduction of tobacco and smoking, there has always been the conception that smoking
causes lung cancer. This was thought to be true as early as the 1920’s. Subsequently epidemiological studies
were performed between the 1930’s – 1960’s to test whether or not smoking was the cause of lung cancer.
Two significant studies were produced by Doll (1947) and Hill (1951).
Doll used a case study report by comparing two different groups of people. The first group of people all had
lung cancer while the other group had various diseases. Both of these groups were asked about their smoking
habits. What Doll found was that a large percentage of the lung cancer patients were smokers while the
control group a smaller percentage were smokers and it was quite possible that their illness was caused by
smoking as well. Doll’s results were as follows:
CASES
TEST GROUP
CONTROL GROUP
Smokers
1350
1296
Non – Smokers
7
61
Total
1357
1357
Hill’s cohort study involved a number of doctors across Great Britain. The study involved the doctors
answering a number of questions on their smoking habits. Those doctors who were smokers were part of the
smoking group, while those doctors who did not smoke were part of the control group. Both groups were
followed over a 10 year period. During this period 133 people died. Of those 130 of them were smokers. The
results were as follows:
DAILY NUMBER OF CIGARETTES SMOKED
0
1 – 14
15 – 24
25+
TOTAL
DEATHS FROM LUNG CANCER
3
22
54
57
133
The above table indicates that the greater the number of cigarettes smoked a day the greater chance of death
by lung cancer.
Subsequently many more epidemiological studies have taken place to illustrate the cause and effect
relationship between smoking and lung cancer. This has lead to a greater awareness of the risk factors
involved with smoking.
Pages 309 to 312 contain further information about smoking and lung cancer.
Identify data sources, plan and perform a first – hand investigation or gather information from secondary
sources to analyse and present information about the occurrence, symptoms, cause, treatment/management
of a named non – infectious disease. (Page 318)
Things to consider:
- This will be a secondary source task. What does gather, analyse and present mean?
- How will you present your findings?
- Choose one disease and be succinct.
DOWN SYNDROME
OCCURRENCE
The occurrence of down syndrome increases with the age of the
mother. The general rule of thumb is that the chance of having a baby
with down syndrome increases with maternal age. However the
chance of having two babies with down syndrome is less then 1%.
According to Wikipedia down syndrome occurs in 1 in 800 – 1000
births however there are many underlying factors which affect this
result.
SYMPTOMS
Symptoms of down syndrome include; mild to sever mental
retardation, small flat nose, skin folds at the eye corners, appearance
of slanted eyes, protruding tongue, small ears, shorter neck, arms and
legs, increase chance of eye defects (often wear glasses) and an
increase chance of heart defects.
CAUSE
There are 3 types of down syndrome. Their causes are outlined below:
Trisomy 21 – occurs in about 92% of down syndrome cases. Trisomy
21 is caused by the presence of an extra chromosome 21 in all cells.
Mosaic trisomy 21 – occurs in about 2 – 4% of down syndrome cases.
Mosaic trisomy 21 is caused by the presence of an extra chromosome
in some of the babies cells.
Translocation trisomy 21 – occurs in about 3 – 4% of down syndrome
cases. Translocation trisomy 21 is caused by chromosome 21 getting
stuck or translocated during conception or growth of the baby during
pregnancy. This results in the baby having 46 chromosomes but
expressing down syndrome symptoms.
TREATMENT/MANAGEMENT
There is no cure as such for down syndrome. However there are
special education programs which can assist children. Many children
with down syndrome can become independent and live normal lives.
Explain how one of the following strategies has controlled and/or prevented disease:
- public health programs
- pesticides
- genetic engineering to produce disease – resistant plants and animals (Page 332 – 333)
Things to consider:
- What does explain mean?
- You only have to choose ONE. Some knowledge on all three could be beneficial (if you have time).
- Be succinct.
Through genetic engineering scientists have been able to produce disease resistant plants and animals. By
increasing our knowledge of certain plants and livestock, and their genetic make – up, humans have been able
to increase food supplies. Genetic engineering is a relatively new study and the full potential of this technique
has not been realised.
For example Australian scientists have produced a genetically modified pea that is resistant to the pea weevil.
The pea weevil consumes large amounts of crops every year in Australia. The gene that confers resistance to
the pea weevil was extracted from the common kidney bean. This gene was spliced into the pea crops. The
result was that the gene produces a certain protein that cannot be broken down by the larvae and hence the
larvae die out.
A simple animal example is humans. In medicine scientists have genetically engineered insulin using
recombinant DNA to help control diabetes.
Perform an investigation to examine plant shoots and leaves and gather first – hand information of evidence of
pathogens and insect pests.
Things to consider:
- What are insect pests? (Rose bush cuttings will be acquired. Look for tiny insects known as aphids.
These insects suck the sap out of the rose bush.)
- What are pathogens? (Look for discolouration of leaves or bulges/growths on leaves and stems
- Refer to page 328 for experimental procedure. Gather your results and write your Conclusion to your
experiment.
ASSESSMENT DOT POINTS
The following dot points will be covered in your assessment task 4. I have not written any responses to these
dot points. However, if you need assistance with these please notify myself as soon as possible.
1. Identify data sources, gather process and analyse information from secondary sources to
describe one named infectious disease in terms of its:
 Cause (name and type of pathogen)
 Historical developments in our understanding of the disease
 Life cycle and / or special characteristics of this pathogen
 Transmission
 Host Response
 Major Symptoms
 Treatment
 Prevention
 Control
2. Process, analyse and present information from secondary sources to evaluate the effectiveness
of vaccination programs in preventing the spread and occurrence of once common diseases,
including smallpox, diphtheria and polio.
3. Discuss the role of quarantine in preventing the spread of disease and plants and animals into
Australia or across regions of Australia.
4. Process and analyse information from secondary sources to evaluate the effectiveness of
quarantine in preventing the spread of plant and animal disease into Australia or across regions
of Australia.
5. Gather and process information and use available evidence to discuss the changing methods of
dealing with plant and animal diseases, including the shift in emphasis from treatment and
control to management or prevention of disease.