Powerpoint

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Understanding OrganismsUnderstanding Organisms
Revision powerpoint
(OCR Gateway)

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B1a – Fitness and HealthB1a – Fitness and Health

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Modern diets and health problemsModern diets and health problems
% obesity in the UK

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The Circulatory systemThe Circulatory system
The circulatory system is responsible
for pumping ______ around the body.
We need blood to be taken around the
body because blood contains ________
and _______. These are needed so
that all the ____ in our bodies can
produce _____ through _________.
Words – energy, blood, glucose,
respiration, oxygen, cells

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Arteries and veinsArteries and veins
Arteries carry high pressure blood away from the heart to the
rest of the body. The blood is under pressure due to heart
contractions.
Veins carry low pressure blood back to the
heart. They have thinner, less elastic walls and
have valves to prevent backflow of blood.

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Heart diseaseHeart disease
Cholesterol

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Heart disease and High Blood PressureHeart disease and High Blood Pressure
Heart disease and high blood pressure are conditions where
the ______ and blood vessels experience extra strain. They
can be caused by:
• Excess weight
• High stress levels
• _____
• Excess _______
• Diets that are high in saturated ___, sugar or salt
Long term high blood pressure can cause blood vessels to
weaken or even ______. To DECREASE blood pressure
regular exercise and a balanced ____ are a good start!
Words – alcohol, burst, smoking, heart, fat, diet

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Measuring Blood PressureMeasuring Blood Pressure
Blood pressure
measurements are
taken in terms of
“Systolic pressure
over diastolic
pressure”.
High blood pressure can cause
heart attacks, strokes, dementia,
heart disease and kidney disease.
Low blood pressure can cause
dizziness or fainting.

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Fitness and HealthFitness and Health
“Having good health” means
“being free from disease”
“Being fit” means “having an
good ability to do physical
activity” and can be measured in
terms of stamina, strength,
agility etc

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SmokingSmoking
Cigarettes contain 3 harmful things:
1. NICOTINE, which is an ___________ drug that raises the
heart beat, narrows the arteries and so causes ____
_____ _____. This leads to heart _________.
2. TAR, which coats the lining of the _______ making them
less able to take in oxygen. It also contains carcinogens
which cause ______________.
3. CARBON MONOXIDE, which is a _______ ____ which
joins up with ____ blood cells making them incapable of
transporting _____________ around the body. In
pregnant women it can cause oxygen deprivation, leading to
low birth ______.
Words – high blood pressure, oxygen, red, addictive,
disease, poisonous gas, lungs, cancer, mass

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Saturated Fat and Heart DiseaseSaturated Fat and Heart Disease

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B1b – Human Health and DietB1b – Human Health and Diet

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Balanced dietBalanced diet
A balanced diet should contain fats, proteins and
carbohydrates in roughly these amounts:
A good balanced diet should also contain water, vitamins,
minerals and fibre.
• Carbohydrates are simple sugars such as glucose
• Fats are made up of fatty acids and glycerol
• Proteins are made up of amino acids

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Factors affecting choice of dietFactors affecting choice of diet
What factors affect
our choice of diet?
Age – teenagers
need more
protein
Religion – some
foods may be
bannedActivity – a
sporty lifestyle
will need more
energy
Personal choice,
e.g. vegetarianism
Allergies

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ProteinProtein
Proteins are long chains of amino acids.
Meat and fish are
“first class” proteins
People who do not eat enough protein will not grow
properly. Protein deficiency can result in a disease
called kwashiorkor, where the muscles waste away and
the belly swells. This is common in developing
countries where overpopulation and limited investment
in agriculture can cause food shortages. Proteins are
used by the body as an energy source if fats are not
present.
How much protein should we eat?
EAR of protein (in g) = 0.6 x body mass (in kg)
There are two classes of protein:
• Essential amino acids (must be eaten)
• Non-essential amino acids (can be made in the
body)

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Storing Food in our bodiesStoring Food in our bodies
How do our bodies store food?
The liver converts glucose
and other carbohydrates
into insoluble glycogen to
be stored in the liver
Fats are stored under the
skin and around organs as
“adipose tissue”
Proteins are not stored in the body.

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Body-Mass IndexBody-Mass Index
A commonly-used way to indicate is someone is overweight or
underweight is the Body Mass Index (BMI):
BMI =
Mass (kg)
Height2
(m2
)
BMI Meaning
<18.5 Underweight
18.5-25 Ideal
25-30 Overweight
30-40 Obese – obesity is linked to
heart disease, diabetes and

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Eating disordersEating disorders
Anorexia nervosa – this is a condition where
sufferers restrict what they eat and
sometimes starve themselves, leading to
possible weight loss, abdominal pains,
discoloured skin, irregular periods etc.
Bulimia nervosa – this is when people vomit or
take laxatives straight after eating to get the
food out as quickly as possible. It can lead to
weight fluctuations, poor skin, hair loss,
irregular periods, tiredness etc.

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B1c – Staying HealthyB1c – Staying Healthy

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PathogensPathogens
Pathogens are microbes (micro organisms) that can cause
diseases. They can enter the body in a number of ways:
…or other
natural
openings…
They can be
breathed in
through the
mouth or nose
They can enter
through cuts or
bites in the skin

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Spreading of PathogensSpreading of Pathogens
Diseases and pathogens can be spread by a number of means,
including:
Cholera
bacteria,
spread in
water
Salmonella
bacteria,
found in food
Influenza virus,
spread through
the air
Athlete’s foot, a
fungus spread
through contact
Malaria, spread
through
“vectors”, e.g.
mosquitoes
HIV, spread
through body
fluids

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Microbes: our defence against themMicrobes: our defence against them
Our bodies have defence mechanisms against microbes:
If our skin is
cut platelets
seal the wound
by clotting
The breathing
organs have hairs
and produce mucus
to cover the lining
of these organs and
trap the microbes
The skin acts as
a waterproof
barrier
Our stomach contains
hydrochloric acid
However, these mechanisms can’t do anything about non-
infectious diseases (e.g. cancer) or inherited diseases
(e.g. cystic fibrosis)

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What pathogens do to usWhat pathogens do to us
Pathogens can cause the
damage or death of cells,
e.g. in liver cirrhosis:
They can also damage the
body by producing toxins:

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White blood cellsWhite blood cells
If microbes enter our body they need to be
neutralised or killed. This is done by
WHITE BLOOD CELLS:
White blood cells do 3 things:
1) They eat the microbe (these
white blood cells are called
“phagocytes”)
2) They produce antibodies to
neutralise the microbe
(“lymphocytes”)
3) The produce antitoxins to
neutralise the poisons produced
by microbes (lymphocytes again)

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Producing antibodiesProducing antibodies
Step 1: The lymphocyte “sees” the
pathogen (microbe)
Step 2: The cell produces
antibodies to “fit” the antigen
Step 3: The antibodies fit onto the
antigens and cause them to “clump”
Step 4: The pathogens are
“eaten” by the white blood cells
You’re going
down

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Specific antibodiesSpecific antibodies
Antibodies are specific for different antigens – they will
only neutralise the microbe they have been made for.

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Fighting diseaseFighting disease
NATURAL IMMUNITY
This is when antibodies are produced by a
person when needed or they are passed on by
the mother during pregnancy.
ARTIFICIAL IMMUNITY
Can be done in two ways:
1) A vaccine with dead microbes (which still carry
the antigen) is injected – the body is “tricked”
into producing antibodies ready for the real
thing. This is called PASSIVE
IMMUNISATION and the body then
“remembers” the microbe by producing memory
cells that “remember” it
2) The antibodies are injected directly into the
body – this is called ACTIVE IMMUNISATION.

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Vaccinations and MedicinesVaccinations and Medicines
Vaccinations have
eradicated some
diseases entirely
but they can
carry some side
effects.
Health problems can also be treated using antibiotics or
antivirals:
• Antibiotics are used to treat bacterial infections but they
have to be used sparingly or the bacteria might become
resistant (e.g. MRSA)
• Antivirals are used to treat a virus, such as HIV.

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The importance of testing drugs – e.g. ThalidomideThe importance of testing drugs – e.g. Thalidomide
Mat Fraser,
comedian and actor
Tony Melendez,
guitarist

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Developing new drugsDeveloping new drugs
Before a new drug can be approved it has to go through a
strict testing process. Consider the example of thalidomide:
Date Event
Mid 1950s
Late 1950s
Early 1960s
Mid 1960s
Animal testing using thalidomide was undertaken.
Tests showed that it was safe but the tests were
“inadequate” – no tests were done on pregnant animals
Thalidomide prescribed to pregnant mothers to help
sleep and morning sickness problems
Babies are born with birth defects and the drug was
banned worldwide. Around 12,000 deformed
Thalidomide babies born, 4,000 die in first year.
Tests show that Thalidomide can help leprosy
sufferers and it is still used today for this purpose.

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Researching new medicinesResearching new medicines
Before new drugs can be approved they have to go through
three stages. What are the advantages and disadvantages of
each stage?
3. Is it safe for humans? Human
volunteers are tested on.
1. Is it toxic? Tests are done on cells
2. Is it safe for animals? Animal tests are
carried out

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PlacebosPlacebos
Clinical trials can be done in different ways:
1) Blind trials
Patients do not know which drugs they are taking – a real drug
or a “placebo”
2) Double blind trial
Neither the doctors or the patients know if they are taking
the real drug
Placebos offer anethical dilemma as a patient might be
sick and still be given a “dummy” pill. Also, you might
notice if you had a placebo as you wouldn’t get the side
effects of normal drugs...

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MalariaMalaria
Parasite
Host
The spread of malaria can be
restricted by:
• Sleeping under mosquito nets
• Taking malaria pills
• Avoiding being bitten

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CancerCancer
Cancer is a disease where cells show uncontrolled growth.
Our diets can affect our chances of getting cancer:
“Good” foods:
Fruit
Vegetables
Fibre
“Bad” foods:
Salt
Saturated fats
Red meat
Exercise can play a key part as well – Cancer Research UK
recommends “30 minutes a day of moderate activity” 5 days a
week, such as gardening, walking etc.

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TumoursTumours
Tumours can be classed as “malignant” or “benign”:
Malignant tumours are cancerous and will still grow
Benign tumours are not cancerous – they may still
grow but won’t spread
This graph shows the
survival rates of different
types of cancer (source:
Cancer Research UK).
What conclusions can you
draw from it?

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B1d – The Nervous SystemB1d – The Nervous System

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Optic
nerve
The EyeThe Eye
Retina
Pupil
Cornea
Ciliary muscles
Blind
spot
Optic
nerve
Lens
Iris
Sclera

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VisionVision
“Binocular vision” “Monocular vision”
What are the advantages and disadvantages of each?

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Seeing thingsSeeing things
Rays of light are refracted
(bent) first by the cornea
and then by the lens. They
focus on the retina.

40. 18/05/16Focussing on different distancesFocussing on different distances
For distant objects the
ciliary muscles relax
and the suspensory
ligaments pull tight
making the lens pull
thin – the light doesn’t
bend as much.
For close objects the
ciliary muscles contract
allowing the lens to go
fat, thus bending the
light more.

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Problems with visionProblems with vision
Short sighted Long sighted
Colour blindness,
caused by a lack
of specialised
cells in the cornea

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Using lenses to correct visionUsing lenses to correct vision
Short Long
Laser eye surgery could also be used, which basically reshapes the cornea

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The Nervous SystemThe Nervous System
The CENTRAL NERVOUS SYSTEM (CNS) enables us to react
to our surroundings. It consists mainly of the brain, the spinal
chord, nerve cells (“neurones”) and receptors.
Types of receptor:
1) Light receptors in the eyes
2) Sound receptors in the ears
3) Taste receptors on the tongue
4) Smell receptors in the nose
5) Touch, pressure and temperature receptors in the skin
6) Changes of position receptors in the ears (balance)

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Nervous ReactionsNervous Reactions
When we react to a stimulus our bodies use the following
pattern:
Stimulus Receptor Coordinator Effector Response
For example, consider a
man and a camel: Oh
No!
What are the stimulus, receptor, coordinator, effector and
response in this situation?

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Examples of reactionsExamples of reactions
Stimulus Receptor
(i.e. the thing
that detects the
stimulus)
Effector
(i.e. the thing
that will do the
reaction)
Response
(i.e. action
taken)
Bright light
Sour taste
Losing balance
Sit on a drawing
pin

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Structure of a nerve cellStructure of a nerve cell
Nucleus Muscle strands
(effector)
Cell body
1) Motor neurone 2) Sensory neurone 3) Relay neurone
Impulse Impulse
Axon
Myelin sheath – increases
the speed of transmission
Dendrons – conduct the
impulse to the cell

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SynapsesSynapses
Neurones never ____ each other – there is a small gap
between them called a _____. A signal is sent from one
_______ to the next by a _______ transmitter across
the synapse. These transmitters are then ________.
Words – chemical, synapse, neurone, touch, destroyed

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Conscious actionsConscious actions
A conscious action is one where the brain makes a considered response.
Here’s what happens:
Stimulus Receptor Sensory Neurone Coordinator
Motor Neurone Effector Response
1) Receptors in
your skin detect
a stimulus
3) Here another sensory neurone
carries the signal to the brain
4) The brain
decides to move
away the hand
5) This impulse is
sent by MOTOR
NEURONES to the
hand muscles (the
effectors) via the
spinal chord…
2) The impulse is carried
by SENSORY NEURONES
to the spinal chord
6) Which then
moves the hand
away

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Reflex actionsReflex actions
Sometimes conscious action is too slow to prevent harm, e.g…
In situations like this
the body bypasses the
brain to produce a
quicker response.
Here’s how it works…

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Reflex actionsReflex actions
1. Receptor
2. Sensory
neurone
3. Relay
neurone in the
spinal chord
4. Motor
neurone
5. Effector
Stimulus Receptor Sensory Neurone CNS
Motor Neurone Effector Response

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B1e – Drugs and YouB1e – Drugs and You

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Cannabis: Pros and consCannabis: Pros and cons
In January 2004 cannabis was changed from a class B drug to
a class C drug. Some people think that Cannabis should be
made legal. What are the pros and cons of cannabis?
Pros:
Cons:

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Drugs Research ProjectDrugs Research Project
Explain and give examples for the following:
1) Define the terms addiction, tolerance, withdrawal symptom and
rehabilitation.
2) Why do people use legal drugs?
3) What are the drawbacks of legal drugs?
4) Alchohol is a legal drug. What does it do to the human body?
5) Why do people use illegal drugs?
6) What are the drawbacks of illegal drugs? What can they cause?
7) Choose one drug and discuss how it affects the human body

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Legal drugsLegal drugs
Drug Effect on
activities
Abnormal behaviour
caused
Caffeine/ other
stimulants
Alcohol
Paracetamol/
other painkillers
Reactions could
become faster
Highly strung, leads
to exhaustion
May make you
drowsy, you
shouldn’t drive
Leads to depressant
effects on the
nervous system
May make you
drowsy, you
shouldn’t drive
Side effects include
dizziness or itchiness
Overall, the effect of these legal drugs can be greater than the effect of
illegal drugs simply because more people use them.

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DrugsDrugs
Drugs are classed as “a substance that affects the central
nervous system, causing changes in psychological behaviour and
possibly addiction”. Some examples:
Type of drug Effects Examples
Painkiller Block nervous
impulses
Morphine, aspirin,
paracetamol
Hallucinogen Distort sense
perception
LSD
Stimulant Increase reactions Caffeine, nicotine,
ecstasy
Depressant Slow down brain
activity
Alcohol, solvents,
termazapam

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Synapses and drugsSynapses and drugs
Depressant drugs can bind with ______ molecules in the
membrane of adjacent _______ and block the
transmission of an ______.
Stimulants can cause more ___________ to cross the
________.
Words – neurotransmitter, receptor, synapse, neurones, impulse

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Investigating Reaction TimesInvestigating Reaction Times
Task: Design an experiment that investigates the affect of
caffeine on reaction times.
Variables: What are the independent, dependant and control
variables?
Results: Draw your own results table:
Conclusion: What do your results show you?

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SteroidsSteroids
Steroids are drugs that are used to boost athletic
performance. They’re banned and using them will lead to
disqualification from competing.
This picture isn’t real…
Ben Johnson, who ran the 100m in 9.79
seconds in 1988 but had his Olympic gold
medal stripped away from him after
testing positive for steroids.

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Smoking revisitedSmoking revisited
Cigarettes contain 4 harmful things:
1. NICOTINE, which is an ___________ drug that raises the heart
beat, narrows the arteries and so causes ____ _____ _____. This
leads to heart _________.
2. TAR, which coats the lining of the _______ making them less able to
take in oxygen. It also contains carcinogens which cause
______________.
3. CARBON MONOXIDE, which is a _______ ____ which joins up with
____ blood cells making them incapable of transporting
_____________ around the body. In pregnant women it can cause
oxygen deprivation, leading to low birth ______.
4. Particulates, which accumulate in the lungs.
Words – high blood pressure, oxygen, red, addictive,
disease, poisonous gas, lungs, cancer, mass

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Diffusion in the lungsDiffusion in the lungs
Oxygen diffuses in and carbon dioxide diffuses out of blood in
the lungs:
CO2

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Damaging the lings (emphysema)Damaging the lings (emphysema)
Before
smoking
After
smoking – less
surface area
Another way smoking can
damage the body is
through destroying the
shape of alveoli:

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More damage by smoking – smoker’s coughMore damage by smoking – smoker’s cough
The “pink” hairs in this photo
show cilia, small hairs lining
the windpipe that clear dust
and other particles away from
the air we breathe. Regular
smoking causes the cilia to
become paralysed and excess
mucous and tar build up in the
lungs, causing smoker’s cough.

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Tobacco and Lung CancerTobacco and Lung Cancer
Sir Richard
Doll, 1912-2005
Over 50 years I proved the link between
smoking and lung cancer. I published my first
findings in 1950, based on patients in London
hospitals, and then studied 40,000 doctors
and proved a link in a paper published in 1954.
Smoking has existed in Western
culture since the 16th Century.
However, scientists only proved the
link between it and various diseases
shortly after the Second World War.

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Cancer Research UK statisticsCancer Research UK statistics
What do these statistics imply?

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The Effects of AlcoholThe Effects of Alcohol
Time Effects
Short term
Long term
Blurred vision, lowering of inhibitions,
slowing of reactions (hence why there is a
limit on drink-driving)
Liver cirrhosis, brain damage
Alcohol content is measured in %ABV.
Wine is typically 12% while beer is 4-
6%. 40% of hospital A&E incidents are
alcohol-related. When the liver
removes alcohol it turns it into toxic
chemicals that cause liver damage or
liver cirrhosis:

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B1f – Staying in BalanceB1f – Staying in Balance

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HomeostasisHomeostasis
Homeostasis means “controlling internal conditions”:
Waste products that need to be removed + how
CO2
Internal conditions that need controlling + how
Temperature
Water content
Produced by respiration, removed via lungs
Increased by shivering, lost by sweating
Increased and decreased by hormones
Some of these mechanisms are controlled by “negative
feedback” systems, i.e. the absence of a particular hormone
causes the reaction to change.

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Measuring Body TemperatureMeasuring Body Temperature
Some possible methods…
Body thermometers/
probes
Heat sensitive strips Thermal imaging
Common places to measure temperature are in the armpit, the
mouth, the fingers, the ears or the anus.

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Controlling Body TemperatureControlling Body Temperature
Wow it’s hot! My body
temperature needs to stay at
37O
C as its the best temperature
for the enzymes in my body. How
does my body keep the
temperature right?
Also, temperature sensors in the skin
detect the heat and send information
to the brain.
The thermoregulatory centre in the
brain detects “warm blood”.
When the brain detects the high
temperature it takes two main steps....

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Maintaining Body TemperatureMaintaining Body Temperature
Cold Hot
Vasodilation
Vasoconstriction
Vasodilation increases heat transfer to the surroundings and
heat is also lost through the evaporation of sweat.

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Heat stroke and hypothermiaHeat stroke and hypothermia

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Body Temperature and the Nervous SystemBody Temperature and the Nervous System
Effectors (muscles and sweat glands)
carry out the response
Nerve endings in the skin detect the
external temperature
Temperature detectors in the brain
detect the blood temperature
The hypothalamus coordinates a
response using hormones

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Controlling Blood Sugar levelsControlling Blood Sugar levels
We need glucose in our bodies to help our cells to respire and
produce energy. What happens if we have too much glucose?
If blood sugar is too high the
pancreas releases insulin, which
travels in the blood stream. Insulin
lowers blood glucose levels by
converting glucose into insoluble
glycogen.
If glucose levels fall too low
then the hormone glucagon is
released from the pancreas
which causes liver to turn
glycogen back into glucose.
The trouble with hormones is
that they are slower than
nervous reactions.

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DiabetesDiabetes
What is diabetes?
What do the pens (above right) do?
What does an insulin injection (above left) do?
What is the difference between Type 1 and Type 2 Diabetes?
How does physical activity affect Type 1 and Type 2
Diabetics?

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DiabetesDiabetes
Type 1 Diabetes is a ________ in which a person’s blood sugar
(i.e. glucose) level may rise to a _______ level. This is
because the ______ doesn’t produce enough _________.
Physical activity will _______ the amount of glucose needed
by the body.
Diabetes can be treated by __________ carefully or by
injecting extra insulin when needed. Diabetics have to test
their blood sugar level before they decide how much insulin to
_______ themselves with. Type 2 Diabetes occurs when the
patient becomes _______ to insulin so the patient will have to
be careful regarding physical activity.
Words – insulin, disease, inject, dangerous, eating, pancreas,
increase, resistant

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B1g – Controlling Plant GrowthB1g – Controlling Plant Growth

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Plant Growth IntroductionPlant Growth Introduction
Plants grow due to their cells dividing through mitosis. The
cells then specialise into root hair cells, palisade cells etc.
Unlike animals, plants continue to grow for the rest of their
lives.

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Plant HormonesPlant Hormones
The growth of roots and shoots is controlled by hormones
called auxins that move through the plant in solution:
In the roots hormones slow
down growth of the cells in
the lower region, which
makes the root bend down.
In the shoots the hormone
auxin is “destroyed” by
light, so the shoot will bend
towards the light as the
cells on the shaded side
grow quickest.

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Some DefinitionsSome Definitions
Shoots grow towards light (positive phototropism) and against
gravity (negative geotropism). This is caused by cell elongation
on the underside of the shoot and this happens because auxin
is made in the tip and is unevenly distributed through the
shoot.
Roots grow away from light (negative phototropism) and in the
direction of gravity (positive geotropism). This is caused by
cell elongation on the upper side of the root.

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Artificial Plant HormonesArtificial Plant Hormones
Hormones can be used to help plant growth and the
development of fruit:
1) Auxin
This hormone helps
fruit to develop
2) Ethene
This hormone helps
fruit to ripen
Other uses include rooting powders (to help root
development), control of dormancy and weedkilling.

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B1h – Variation and InheritanceB1h – Variation and Inheritance

82. 18/05/16
VariationVariation
“Variation” is the name given to differences between
individuals of the SAME species.
Variation is due to GENETIC or ENVIRONMENTAL causes.
For example, consider dogs:
1) Ways in which they are the
same:
2) Ways in which they are
different:

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VariationVariation
Variation means “differences within a species. For example,
consider some of the people in your class:
Ways in which they are the same Ways in which they are different

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Environmental differencesEnvironmental differences
Some of this variation is due to our parents, but some of it is
due to our upbringing and the environment in which we live –
this is called “Environmental variation”.
Variation due to
inheritance only
Variation due to
environment only
Variation due to a
bit of both

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Genes, Chromosomes and DNAGenes, Chromosomes and DNA
Humans have 23 pairs of chromosomes. Different species

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Sexual ReproductionSexual Reproduction
The human egg
and sperm cell
(“GAMETES”)
contain 23
chromosomes
each.
When fertilisation happens the
gametes fuse together to make
a single cell called a ZYGOTE.
The zygote has 46 chromosomes
(23 pairs) and contains
information from each parent.
We have similar characteristics to our parents due to genetic
information being passed down in genes through gametes:

87. 18/05/16
Sexual vs. Asexual reproductionSexual vs. Asexual reproduction
Sexual reproduction:
•2 parents are needed
•Offspring will have “pairs” of chromosomes
•This will cause genetic variation
Asexual reproduction:
•Only 1 parent needed
•Offspring are GENETICALLY IDENTICAL to
parent (“clones”)
“Snuppy” – the
first cloned dog
(Aug 05)

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Boy or Girl?Boy or Girl?
X Y X
XX XY
Girl Boy
“Allele”

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Father
Mother
Son
Daughter
Boy or Girl?Boy or Girl?

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Key wordsKey words
Genotype
Phenotype
Allele
Dominant
Recessive
Homozygous
Heterozygous
•This allele determines the development of a
characteristic
•The characteristic caused by the genotype
•This allele will determine a characteristic only if
there are no dominant ones
•This word refers to a pair of chromosomes being
made of two different alleles of a gene
•The genetic make up in a nucleus
•This word refers to a pair of chromosomes being
made of two of the same alleles of a gene
•An alternative form of a gene

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Eye colourEye colour
In eye colour the brown eye allele is dominant, so we call it
B, and the blue eye is recessive, so we call it b:
bbBB Bb
Homozygous
brown-eyed
parent
Heterozygous
brown-eyed
parent
Blue-eyed parent
What would the offspring have?

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Eye colourEye colour
Example 1: A homozygous
brown-eyed parent and a
blue-eyed parent:
Example 2: 2 heterozygous
brown-eyed parents
BB bbX Bb BbXParents:
Gametes:
Offspring: Bb Bb BbBb BB Bb bbbB
B B bb B bB b
(FOIL)
All offspring have brown eyes 25% chance of blue eyes

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Eye colourEye colour
Example 3: A heterozygous brown-eyed
father and a blue-eyed mother:
Bb
Bb Bb bbbb
bb
b bB b
Equal (50%)
chance of
being either
brown eyed or
blue eyed.

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B b
b
b
Another method – the “Punnett square”Another method – the “Punnett square”
Example 3: A heterozygous brown-eyed
father and a blue-eyed mother:
B b
b Bb bb
b Bb bb
Father
Mother

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Example questionsExample questions
1) In mice, white fur is dominant. What type of offspring
would you expect from a cross between a heterozygous
individual and one with grey fur? Explain your answer with a
genetic diagram.
2) A homozygous long-tailed cat is crossed with a homozygous
short-tailed cat and produces a litter of 9 long-tailed kittens.
Show the probable offspring which would be produced if two
of these kittens were mated and describe the characteristics
of the offspring (hint: work out the kitten’s genotype first).

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Inherited diseasesInherited diseases
1) Cystic fibrosis – a disease that causes thick and sticky mucus to coat
the lungs, gut and pancreas, making breathing and digestion difficult. It’s
caused by faulty recessive alleles:
2) Huntingdon's disease – a disease of the nervous system that causes
shaking, memory loss, mood changes and eventually dementia. It’s caused
by a faulty dominant allele:
3) Sickle cell anaemia – a disease that alters the shape of red blood cells,
thereby reducing their oxygen capacity, causing weakness and anaemia.
It’s caused by recessive alleles:
Ff FfX
Cc ccX
Ss SsX

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Family Pedigree ChartsFamily Pedigree Charts
18/05/16
Consider the following chart of the offspring and
grandchildren between two sickle-cell anaemia carriers:
Key:
= male
= female
= S allele
= s allele
Q. Describe the genotype and the phenotype of each
of the grandchildren. Also, which member of this
family has got sickle-cell anaemia?

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The debate over genesThe debate over genes
The “Nature vs Nurture” debate is all about whether or not
certain attributes or abilities are down to genetic reasons or
through upbringing, e.g.:
Intelligence
Sporting ability
Good health