Entering the world
of biosciences
Private Bag X894
Pretoria 0001
www.dst.gov.za
T
his booklet aims to give readers, whether the
scientists of tomorrow or the curious at heart,
a glimpse into the fascinating world of biosciences.
The dictionary defines this particular scientific field
as: “Any of the branches of natural science dealing
with the structure and behavior of living organisms.”
A synonym is life science, and simplistically
speaking, life, regardless of its shape or form, begins
with a cell.
Published by the South
African Agency for
Science and
Technology
Advancement in
accordance with the
DST initiative to
promote
BioSciences.
211 Skinner Street
Didacta Building
Pretoria
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Printing & Repro:
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Thus, as part of its commitment to enhance
public awareness around biosciences and especially
South Africa’s wealth of bioresearch, the National
Department of Science and Technology compiled
this resource booklet to start with the very basic
essence of life.
It looks at some of the building blocks of genetics: DNA (Deoxyribonucleic Acid), inheritance,
and enzymes. Each with an easy-to-follow experiment. Then it takes a closer look into the genetic
highlights and challenges of marine biology in a
growing field of research in South Africa.
Why is the coelacanth important? And why should
we pay any attention to the great salt waters that
cover more than two-thirds of planet Earth?
Read on and find out!
1
CUT-AWAY OF AN ANIMAL CELL.
BIOSCIENCES: GENETICS
Many bricks make
walls. Many cells
make tissue
2
Golgi body
PACKAGING & export
of new proteins
E
ach cell is a dynamic, living little factory. It is the
smallest living unit that can
carry out the basic functions
of life: growth, metabolism
and reproduction.
Some simple organisms
are made up of only one cell,
while most plants and
animals are made up
of huge numbers
of cells. Each cell
has its own role
to play in the
life of the plant
or animal and is
adapted to perform
those particular functions. Your skin, your
bones, your muscles and your
brain are all made of cells.
Nucleus
CONTROL
CENTRE
Many cells
make tissue.
Tissue make
up a body.
There are over 200 different
types of cells in your body.
Mitochondrion
ENERGY
Inside a cell
A living cell is a squidgy
pocket containing cytoplasm
(sai-tow-plazim), which is a
watery, jelly-like mixture of
chemicals.
A thin skin, called
a membrane, holds
the cytoplasm
together. Animal
cells have soft
membranes made
of fat and proteins.
The membrane gives
the cell shape, and also
lets certain chemicals like
oxygen and food substances
pass through to feed the cell,
Cell membrane
PROTECTION
Endoplasmic
reticulum
PRODUCTION
of new proteins
Oxygen & food
substances
Illustration: Cobus Prinsloo
Nearly all
living things
– plants
and animals
(including
us humans)
– are built
up from tiny
pockets, called
cells. Cells are
so small that
they can only
be seen under
a microscope.
Cytoplasm
but it stops others. It lets
waste material out again. (See
for yourself how this works in
the experiment on page 6)
Plant cells have a tough
membrane made of material
called cellulose. The cellulose
can sometimes be very thick
and so gives the plant its
shape.
The cytoplasm acts as
Waste
a storeroom of molecules
for growing and repairing
the structures inside the
cell. Small structures called
organelles are present in the
cytoplasm. They produce hormones, enzymes and other
substances which are released
for use inside the cell and
also elsewhere in the body.
Most plant and animal
3
How many?
There are about a
hundred million cells
in your body, with
many different types
with specific functions.
How small?
At least 1000 cells
would fit side by side
across a full-stop.
Skin cell
Muscle cell
Nerve cell
4
cells contain an inner part,
called the nucleus. It controls
what the cell does and how it
develops. The nucleus can be
seen under a microscope.
The vacuole is a space in
the cell containing air, liquids
or food particles. Animal cells
usually have small vacoules.
All plant cells have vacuoles
and the liquid inside them is
called cell sap. Plant cell vacuoles are quite large. Water
collects in the vacuoles when
the plant is watered and this
makes the plant rigid (or
stiff). Without enough water,
there is less pressure in the
vacoules and the plant wilts.
Plant cells also contain
chloroplasts, which are tiny
disks full of a green substance
called chlorophyll. They trap
the light energy that plants
need for making food by photosynthesis.
The cells in your body
Just like a house is built
of bricks, your body is made
up of cells. The type of brick
determines what the building will look like. In the same
way, the type of cell determines what type of organ
it will form. There are skin
and blood cells that look like
plates, liver cells that look
like little boxes, fat cells that
are round, and many others.
They still all have the same
basic structure.
All these cells grew from
a single cell made when a
sperm cell from your father
met an egg cell from your
mother and fertilised it. This
one cell contained all the
instructions necessary to
make you. You grew because
that single cell divided to
make two cells, those two
The egg - an amazing cell
There is a type of single cell that you can
see without the aid of a microscope - an
egg. Even an enormous ostrich egg is only
a single cell! These cells are marvelously
adapted to produce new creatures.
Every kind of animal produces eggs, but
they do not all lay eggs. Female mammals,
including people, produce very small eggs
which they keep inside their bodies.
Take a look at a chicken egg. It is a fascinating thing which we take for granted. To us, a
chicken egg is something you boil or fry, or make into an omelette.
But an egg contains some of the clues to the whole mystery of life.
The egg contains a supply of food, known as the yolk. Most eggs
are surrounded by one or more membranes to protect it. The outer
membrane often forms a hard shell.
Each egg contains a very small germinal disc. In unfertilised eggs,
the germinal disk remains so small and does not divide. These are
the eggs that reach our tables. In fertilised eggs, which are produced for hatching chickens, the germinal disk will divide and a
young bird will grow.
divided to make four, and
so on. We call this cell division and that is how all living
things grow.
Cells are always wearing
out. They are then replaced
by new ones. Some cells last
months, and some less than a
day. Nerve cells last for a very
long time.
5
E g g - s p e ri m e
P l a c e
two
eggs
in a jug of
v i n e g a r.
Watch
the eggs
for several minutes. You will see
how the egg shells seem
to bubble. That is the vinegar,
an acid, eating away at the calcium of the egg shell. There is
a chemical reaction between the
vinegar and the shells. The bubbles
are carbon dioxide gas, the result of
the reaction. Let the eggs stay in the
vinegar, completely covered, for 1
- 3 days until the vinegar has ‘eaten’
away the shell on the eggs.
Remove the eggs from the vinegar
and carefully rinse them off, getting
rid of any shell that did not come
off.
If the shell does not come off completely, put the eggs back in the jug
of vinegar, and try to rinse them the
next day.
Have a good look at these eggs.
Even though they no longer have
shells, they still don’t fall apart.
This is because membranes
hold them together. Can you
see the membranes? And
the yolk? Look carefully
to see if you can see
the germinal disk.
Measure
equal
amounts
of
distilled
6
nt
w a t e r
and syrup (or
honey) in each
transparent glass
cup. Place one egg
in each cup and cover
the cup with plastic wrap.
Make a mark on the cup to
show the height of the liquid
inside. Keep the eggs in these
solutions for three days, then
see and feel what they look like.
You will see that the egg in the
water did not change much. The
egg in the syrup will have shrunk
and will feel all wrinkly. Now place
this egg in a new cup, containing
water. The egg will swell up again,
maybe even bigger than its original
size.
What happened?
At first all the water molecules inside
the cell (egg) wanted to move out to
the syrup or honey where there is less
water - or a lower concentration.
Then, when the egg had shrunk, all
the water molecules outside the
egg wanted to move inside to the
lower concentration.
The reason only water moves
across the membrane while
the sugar particles in syrup do
not, is that sugar particles
are too big to cross the
membrane.
Enzymes
– the fire in our bodies
Have you
heard or
seen advertisements
for washing
powders that
claim the powders contain
enzymes that
can remove
specific stains?
Are the claims
of the manufacturers true?
Let’s see…
O
ur bodies use food to
give us energy. Some
foods, like proteins such as
gelatine and starch, need to
be broken down before our
bodies can use them. The
units, or molecules that make
up proteins and starches
are large, but they again are
made up of smaller units.
This breaking down of the
larger units into smaller ones
is called digestion. Our bodies use enzymes to burn the
foods (or digest them) for
their energy.
The enzymes which help in
digestion are specialists. An
enzyme which would digest a
protein will not digest starch,
nor would a starch-digesting
enzyme break down proteins.
To see how an enzyme can
break down proteins, and at
the same time see if the
claims of manufacturers
of washing powders are
true, try the following two
experiments:
Hole in the jelly
Read the instructions on
the packets carefully and
prepare two dishes of clear
jelly, one of gelatine, and the
other of agar.
On each jelly, put a small
pinch of an ordinary powder
detergent, and of a so-called
biological washing powder.
(See the sketch on page 8).
The biological
powder
• Tw
os
dish mall p
last
es
•G
ic
elat
i
ne
•A
gar
aga (you c
an
r
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ps l
pec y
ike
ialis
or E
Br
t
x
Pre perilab ainwav
tori
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i
n
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• A cher to ask y
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• A hing p
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og
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was
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7
START
RESULT
GELATINE
Ordinary
washing
powder
hole
Biological
washing
powder
AGAR
AGAR
is made in Japan
from seaweed, and
is used in cooking
and confectionery.
It can be made up
into “jelly” just like
gelatine.
CATALYST
Something that
allows or encourages
chemical reactions to
take place, while it
remains unchanged
itself.
8
Biological
washing powder
is supposed to contain an
enzyme which ‘removes difficult stains like egg, gravy and
blood’. These contain proteins. If this is a true claim,
we would expect to find the
gelatine (a protein) dissolved
away under the ‘biological’
washing powder, but not
under the ordinary powder.
The agar (not a protein)
should not be dissolved by
either. The jelly might soften
a little for many reasons,
no holes
but do not
be misled by
this. Look for
a great hole
in the jelly.
Try this
experiment
and see what
you find. If
there is a
hole in the
gelatine
under the
biological
washing powder, but not
one under
the ordinary
washing powder, then the
claims of the
manufacturer
are true.
Get rid of the yolk
Boil two standard eggs
together, and push two teaspoons into the yolks so that
there is some yolk left on the
spoons. You may now eat the
rest of the eggs!
Dissolve equal amounts
of ordinary and ‘biological’
detergents in two separate
glasses of water, and leave a
yolk-stained spoon in each
glass. After some time you
ENZYMES …
… are special catalysts in our bodies which allow changes such as a
kind of burning to take place very gently.
Digestive enzymes convert food to simpler substances, but many
other enzymes work in the opposite way, linking simple substances
together to form the more complex ones needed to build up tissue.
Enzymes themselves are made of protein.
Enzymes work best at a particular temperature, which is one of the
reasons why our bodies are kept at constant temperatures.
• Two eggs
• Two glasses
• Biological washing
powder
• Ordinary washing
powder
will see that the spoon in
the ordinary detergent still
has yolk on, but the yolk on
the other spoon has been
digested by the ‘biological’
detergent. This will happen
if the ‘biological’ detergent
really contains enzymes that
break down the proteins in
egg yolk.
Biological
washing
powder
No egg
yolk
Ordinary
washing
powder
Egg yolk
9
In the centre
of every plant
cell - from
algae to sunflowers - and
in the centre
of every
animal cell
- from snails
to you and
me - there’s
a copy of the
organism’s
genetic
material.
DNA
T
he DNA carries a complete blueprint of the
organism. It’s what transfers
characteristics from one generation to the next.
At the chemical level the
cells of all plants and all
animals contain DNA in the
same shape - the famous
“double helix” that looks
like a twisted ladder. What’s
more, all DNA
molecules
- in both
plants
and animals
- are made from the same
four chemical building blocks
- called nucleotides. What
is different is how these
four nucleotides in DNA are
arranged.
Genetics
Genetics is about
storing and passing on
messages.
Tissue
These genetic messages are
stored in your DNA, which
is inside almost every cell
in your body. DNA tells
cells what they’re supposed to do, when,
where and how
Cell nucleus
- to keep
Cell
your body
working well.
Our understanding of genetics
stems from the discovery of the DNA molecule
in every cell, which carries
the genetic information.
What is DNA?
DNA is an acid that carries
(as genes) all the information which we inherit from
our parents. It controls everything about the way you
look, from the colour of your
eyes to how tall you are to
the width of your feet. Your
DNA is like your thumbprint.
It is yours and yours alone.
Unless you have an identical twin, no one else on the
planet has exactly the same
DNA strands
tightly coiled into
chromosones
DNA as you.
James Watson and
Francis Crick found out
that DNA looks like two
threads twisted around
each other, held together
by many bridges between
the strands. It almost looks
like a spiral staircase. This
shape is called a double
helix. The genetic information is stored on the threads.
Where can DNA be
found?
In the nucleus of almost
every cell in your body,
and that of every other living thing, is the collection
of DNA needed to make
you. DNA in the nucleus
is grouped into 23 sets of
chromosomes that are called
your “genome”. In each
chromosome, the DNA is
grouped into “genes”. Your
genome contains about
35,000 genes. Each gene
carries information that tells
the cell to make a unique
protein that will perform a
11
special function.
How does something as
small as DNA molecules contain all of the instructions to
make your whole body and
keep it working? Just as a
large number of words can
be made from only a few letters, so DNA can make lots of
different instructions from a
few building blocks.
1953 - 2003
From a poster by Rapid Phase (Pty) Ltd for the
Public Understanding of Biotechnology programme.
In 2003, the world celebrated the 50th anniversary
of the discovery of the DNA structure. In 1953, Francis
Crick and James Watson published the first accurate model of the DNA molecule.
12
How knowledge about
DNA affects us
Scientists are working to
understand the genetic messages that make some people
respond to medicines differently than others and make
some people more prone to
certain diseases than others.
They use this knowledge to
make new medicines to help
people live healthier lives.
DST launched a three-year
programme to tell South
Africans about Biotechnology
(see www.pub.ac.za). This is
the part of science that uses
the DNA building blocks of
life to make useful products
from living things.
The patterns of
inheritance
By Professor Valerie Corfield
Where did
you get
those eyes,
that nose?
Designer babies
New DNA technology
that allows scientists to
read genes raises the
question of whether
they can use the
information to produce
designer babies. Will
parents be able to
order a baby boy with
G
enes come in pairs
because they are carried
in paired chromosomes. Only
one gene of each pair goes
into the sperm or egg that
fuse together (at conception)
to make a baby.
New technology showns
us that very small differences
in the DNA code in our genes
result in different versions of
genes. These genetic differences make us look different
from each other, for example
whether we have blue or
brown eyes. How does this
work?
• One of every pair of
genes that your mom has
came from her dad (your
grandpa)
• The other pair of genes
came from her mom (your
grandma).
• When these genes were
separated into the egg that
made you, you inherited
either the version of your
grandpa’s or your grandma’s
gene.
• The same is true for the
genes you inherited from
your dad. You have either the
version that came from his
mom or his dad (your other
grandma or grandpa).
• If you have brothers or
sisters, chance will determine whether they got the
same version of each gene as
you, or whether they got the
other version. That is why
you look different from each
other.
What happens if you
inherit two different
versions of a gene?
What happens if you
inherit two slightly different
instructions, for example,
the one to make blue eyes
and the one to make brown
eyes? Inheritance follows
its own laws and often one
gene version ‘wins’ over the
13
an IQ of 200, with the
ability to be a gold
medal winner in the
sport of choice, with
blue eyes or brown
eyes and with model
good looks?
As scientists begin to
understand all the
information written
in our DNA, they
will certainly be able
to tell which genes
specify desirable or
undesirable traits.
(Continued on page 16)
other one. The feature (trait)
controlled by that particular
gene is called dominant. The
one that ‘loses’ out is called
recessive.
Brown eye colour is dominant over blue eye colour,
so if you have one gene version instructing your body to
make blue eyes and the other
telling it to make brown
eyes, the brown-eye gene
will ‘win’. Recessive traits are
only seen if you inherit two
copies of the gene that codes
for it, for example, if you get
the blue-eye gene from both
your mom and your dad.
Following the
patterns and laws of
inheritance
The laws that govern
inheritance were first studied
by an Austrian monk called
Gregor Mendel in the 1800’s.
He worked with peas but his
discoveries apply to humans
and animals too. They have
helped people who study
genetics to understand how
individual traits are inherited
and the patterns seen are
called Mendelian inheritance.
Mendel’s laws are applied in
plant and animal breeding
programmes and are used
in genetic counselling
in families who suffer
from inherited diseases.
An experiment in
ure
ext
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genetics
r
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You can do an
• E air co mple;
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Grandparents
Features
Features
Dad
ance, and you will be
From a poster by Rapid Phase (Pty) Ltd for the
Public Understanding of Biotechnology programme.
You,
brothers
& sisters
14
Mom
Features
able to see if they show a
dominant or a recessive pattern of inheritance. However,
some inherited features are
more complicated, so do not
be surprised if some of the
features you choose do not
fit a straight forward pattern
of inheritance.
1) Make a list of what
features you want to study
in your family. Look at some
ideas on the note.
15
Recently, for example, they identified a
version of a gene
that encourages people to overeat and
become fat.
They also know of
two genes that give
a person greater
athletic ability and
they can tell if that
person is likely to be
a good sprinter or a
long distance runner.
However, changing
the DNA code to
put new forms of
designer genes into
a baby who hasn’t
inherited them from
one of the parents is
not yet possible.
In the end these
are issues of right
and wrong that
will guide scientists
as to how far they
should interfere with
nature to produce
designer babies.
It is up to you, the
younger generation,
to understand and
debate such issues.
16
Any other feature characteristic of your family
(remember the story of the
Hapsburg lip in the previous
issue?). What about other
body parts, e.g. hand and
foot shapes? You can look at
photographs or ask your parents about their grandparents
and even their great grandparents. Don’t forget your
aunts and uncles and your
cousins.
2) Draw a pedigree showing all the relatives that you
can investigate. Here is an
example of how geneticists
draw a pedigree. You can
change this to fit your family.
3) Write the version of
each chosen trait (such as
curly or straight hair) under
each relative on the pedigree.
If you have studied a lot of
different traits, you might
want to use abbreviations so
that you can list them under
each person on your pedigree.
4) What features ‘run’ in
your family? Can you see
examples of dominant traits
(e.g. dark eye colour, dark
hair colour)? Can you see
examples of recessive traits
(e.g. red hair, chin dimple)?
Extract DNA
from wheatgerm
By Professor Valerie Corfield
T
his experiment will allow
you to extract one of the
building blocks of life – isolated DNA – from plant cells.
Although each DNA molecule
is too small to see, if you follow the instructions, you will
end up with visible DNA.
• A cup of wheatgerm
(from health shops or
some grocery stores)
• Table salt (about 8
heaped teaspoons full)
• Clear alcohol (cane spirit, gin or rubbing alcohol
from the chemist)
• Green dishwashing liquid (not the gel type)
• Lemon juice (fresh or
bottled)
• Two glass bottles or
large glasses
• A sieve or strainer
• Clean water
Break down the cell walls
of the wheatgerm
In a large glass, dissolve
one level tablespoon of salt
in 300 ml of tap water. Add
four squirts of lemon juice.
Now add half a cup of wheatgerm to the solution and
stir gently for 15 minutes.
The lemon juice will break
down the cell walls of the
wheatgerm. Press this mixture through the sieve and
discard the liquid. You will
be left with a soggy pulp. Do
the same for the other half a
cup of wheatgerm. The pulp
you now have contains the
cell contents without the
cell walls.
Dissolve the DNA
Put one level tablespoon
of salt in 300
ml of
water,
stir the mixture until the
salt is dissolved and add six
teaspoons of alcohol. Add
nine large drops of the washing-up liquid and stir gently.
Add the soggy pulp from
step one and stir it gently
for about 20 minutes. During
this period, the detergent in
the washing-up liquid will
dissolve the DNA into the
mixture. Now add about 10
level teaspoons of salt and
stir gently for 10 minutes.
Separate the
DNA solution
DNA fact file
• DNA stands for
deoxyribonucleic acid.
• It is a chemical
substance made from
building blocks that
form long, thin strings.
• The DNA strings,
called molecules, are
packed very tightly into
the nucleus of cells.
• The DNA molecules
twist around each
other and form a spiral ladder – the DNA
double helix.
• DNA double helixes
are organised into 23
pairs of chromosomes
in every cell in your
body.
• This set of chromosomes is the instruction
manual to make YOU.
• Each different
instruction is called a
gene.
• The gene instructions are written in
a DNA code – the
genetic code.
• New coded copies
are made when the
DNA double helix
unzips down the
middle.
from the mixture.
This step is easy. Just let
the mixture stand and allow
the solids to settle out.
Then gently pour the liquid
into another glass, until it
is about a quarter full. Take
care that the solids do not
mix with the solution. The
solution in the new glass
now contains the DNA in a
dissolved form.
Extract the dissolved
DNA from the solution
Take the quarter-filled
glass, fill it up with alcohol
and stir very gently. As you
stir, you will notice that the
DNA precipitates out as very
fine white threads. You can
leave this mixture to further
allow the DNA to settle.
Gently pour the liquid off and
there … you have DNA!
When DNA is
detective…
FACT FILE
SCIENTISTS
SOLVING CRIMES
Forensic science is the
study of objects that
relate to a crime. This
evidence is analysed
by the forensic scientists, who observe,
classify, compare,
count, measure,
predict, and interpret
data.
18
By Professor Valerie Corfield, US/MRC Centre for Molecular
and Cellular Biology, Faculty of Health Sciences, University
of Stellenbosch
J
ust like fingerprints, every
human has unique DNA.
Scientists have found ways to
tell one person’s DNA from
another person’s; but unlike
fingerprints, which can be
changed using surgery, you
can’t change your DNA. Also,
unlike fingerprints, which are
only left at a crime scene if
a person touches a suitable
surface with bare fingers,
DNA is tucked away in the
centre of every cell in your
body. DNA can be extracted
from hairs, skin cells, blood,
skeletons, bits of bone, teeth
and body fluids left after a
crime. So when traditional
fingerprints are fuzzy and not
much help, DNA fingerprints
can speak out loud and clear.
DNA can last for a long
time, especially when it
is protected inside bones
and teeth. Scientists have
developed ways to extract
DNA and to do DNA fin-
Things have come a long way since
the days of Sherlock Holmes, when
the only tools a detective had were a
sharp eye, a magnifying glass and a
logical mind. Now police and scientists
have many new tricks to help solve
mysteries and crimes (forensic
science). These include:
•
•
•
•
•
•
•
•
•
•
autopsy (examining the dead body for evidence)
“traditional” fingerprinting
matching blood types (Are you O, A, B or AB?)
dental records
ballistics (study of guns)
chemical and fibre analysis (clothing etc)
x-rays
computer modelling
forensic entomology (study of insects)
DNA fingerprinting.
gerprinting tests from very
small amounts of material,
like a dried blood spot or
even from cells in saliva left
over from a person licking a
stamp.
DNA fingerprinting has
provided evidence used to
convict thousands of criminals. It also enables scientists
to look at old cases using
stored samples and evidence.
This has allowed many prisoners who were found ‘guilty’
to be set free
when DNA tests
showed that they
did not commit the crime.
DNA fingerprinting was also
indispensable in identifying
victims of the September 11,
2001 bombing of the World
Trade Centre in the United
States, when scientists only
had scraps of tissue or shards
of bone or teeth to work
with.
DNA fingerprinting has
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FACT FILE
HOW TO BECOME A
FORENSIC SCIENTIST
Forensic scientists
work in the laboratory, in the field and
in the courtroom. To
become a forensic
scientist you will need
a bachelor’s degree in
science (chemistry and
biology); good speaking skills; good notetaking and writing
skills; curiosity and
personal integrity.
also been used to solve longstanding mysteries and identify people who pretended to
be someone else (imposter).
It can also be used to identify how people are related
(parentage), such as in the
case of Happy Sindane. In
addition, mummies and skeletons that are hundreds and
thousands of years old can
now “tell us” if they are male
or female, healthy or sick,
related, even what they had
for dinner, helping scientists
to reconstruct the details of
how these people lived. If
only they’d tell us where they
hid the treasure...
But what exactly is a
DNA fingerprint?
From a poster by
Rapid Phase (Pty)
Ltd for the Public
Understanding of
Biotechnology
programme.
20
A DNA fingerprint looks
very different from an inky
thumbprint on a page. So
what does it look like and
how are these DNA fingerprints made?
When police have a suspect, they take a blood
sample from that person and
take the DNA from the blood
cells. The forensic scientists
then focus in on specific
areas of the DNA that show
small differences between
two people. The differences
between these different
parts of the DNA generate a
pattern, like a supermarket
barcode, that is unique to
the person the scientists are
investigating. This ‘barcode’
is called a DNA fingerprint.
Sometimes at crimes scenes,
only a very small amount of
DNA, such as one hair, is left
behind. In cases like these,
the target areas of the DNA
can be ‘copied’ so scientists
then have enough to make a
DNA fingerprint.
BIOSCIENCES: MARINE BIORESEARCH
Discovering a
“living fossil”
C
ILLUSTRATION: COBUS PRINSLOO
Coelacanths
(pronounced
sea-la-cants)
are ‘living
fossils’ dating
back millions
of years to
well before
the time of
the dinosaurs.
oelacanths, like dinosaurs, were known only
from fossils cast in ancient
stone. Scientists believed
they been extinct for over 70
million years. Then, astonishingly, fishermen found a
strange, blue fish - a living
coelacanth - in their nets
near East London in 1938.
This discovery shook the
scientific world.
The coelacanth made the
headlines again 14 years
later, when one was caught
in the Comoros and flown
to South Africa for study
by Professor JLB Smith.
Thereafter, a number of
these fish were caught in the
Comoros, off Mozambique
and Madagascar.
Three years ago, a group
of divers amazed the world
when they discovered coelacanths swimming in South
Africa’s Greater St Lucia
Wetland Park at a depth
of just over 100 metres.
Nowhere else in the world
are coelacanths in such shallow water and so accessible
21
The Jago submersible is used
to study coelacanths.
BIODIVERSITY AND THE
HEALTH OF PLANET EARTH
We need biodiversity (many different forms of life) on
Earth if we want to live here. Biodiversity shows how sick
or healthy our planet is.
There are three types of
diversity that indicate our
planet’s health:
• Ecosystem diversity: The
variety of environments on
Earth, made up of different habitats. The Greater
St Lucia Wetland Park is an
example of a habitat.
• Differences between species: A species is a particular
kind of organism. There are
about one million known
animal species and over
350 000 known plant species. All members of a species have the same general
22
appearance and behaviour.
The coelacanth is an example
of a species. The members of
a species breed among themselves and, because the same
mixture of chromosomes and
genes is passed to the new
generation, the offspring are
of the same kind.
• Differences within species:
In a species, there can be lots
of variation between individuals. If you look at your
friends, they are all slightly
different though they are all
members of the human species. Coelacanths will all also
differ from one another.
to research. As a result of
this find, the South African
government launched the
Coelacanth Programme in
2002.
These unique prehistoric
creatures provide scientists
with an extraordinary window to the past, allowing us
to look back in time. They
also unlock the door to the
future, opening opportunities
to explore the deep reefs of
the sea, and to research our
marine resources. This will
allow people who depend
upon the sea to have a better
future.
The coelacanth allows
young and old to participate in ‘living’ history in an
exciting chapter of southern African science. The
Coelacanth Programme’s
research ship is often opened
to learners and educators.
There they get information
about careers associated with
deep-sea exploration, from
being a scientist, captain of a
ship, electronics technician to
an engineer in charge of huge
engines.
The coelacanth and
biotechnology
A picture taken
during a December
2000 expedition by
Christo Serfontein,
in Jesser Canyon,
Sodwana.
Biotechnology plays a big
role in the studies of the
coelacanth. All the information which coelacanths
inherit from one generation
to another is stored in their
DNA as genes (see page 10).
Biotechnology is the tool to
measure all these genetic
differences of the coelacanth
DNA.
The more genetic differences there are, the better,
as it means the coelacanth is
more likely to survive changing conditions and new diseases. If there is little genetic
variation, the coelacanth
could possibly be wiped out
by a new disease as it is less
likely to have the gene needed to fight the disease.
Studying the genetics of
coelacanth populations will
answer many of our questions regarding this fascinating fish. It will tell us if the
South African population is
unique or similar
to those found
in other parts of
the world; if the
individuals in
South Africa are
all members of one family;
and if the population is large
enough to breed and survive.
Members of the research
team are collecting scales
from coelacanths without
disturbing or harming them.
Scales grow back rapidly to
replace those that had been
removed. Scale samples
have been collected from six
individuals to date to study
the genetics of the coelacanth. The scales have so far
shown that the South African
group is closely related to
populations elsewhere off
Africa.
Four-limbed animals
The coelacanth is very
important to biologists
studying the evolution of
four-limbed animals (tetrapods). Learning more about
the genome (sets of chromosomes containing genes)
structure and biology of the
coelacanth will tell scientists
lots about the evolution of
modern day vertebrates. The
coelacanth genome may offer
a glimpse of the genomes of
creatures that evolved into
modern day tetrapods over
400 million years ago.
Sources: African Coelacanth Ecosystem Programme;
Public Understanding of Biotechnology Programme
23
Discover our oceans and seas
Volcanic island
Continental shelf
Mid-ocean ridge
24
Seamount
Mud & sediment
from rivers
Deep ocean trench
Ocean bed
Plates move apart
Plates move apart
Hot magma rising
T
here are five large oceans
on Earth: the Atlantic,
the Pacific, the Indian, the
Arctic and the Southern (or
Antarctic) Oceans. They are
really one ‘world ocean’ – a
continuous expanse of water
– with the continents of the
world like big islands of land
in this. We use and exploit
the oceans extensively for
food, energy and materials,
and they have a major role in
controlling our climate.
What lies beneath
the surface?
Until quite recently, we did
not know much about the
dark depths of the oceans.
Now, with the help of small,
manned underwater vehicles,
and unmanned remote-operated vehicles, we can explore
the world beneath their surface.
Explorers found that each
ocean is shaped like a basin
with a rim. The rim is called
the continental shelf. Here
the water is less than 200
metres deep. The real ocean
bed lies 4 000 metres or
more beneath the surface.
This is a large, dark area that
stretches for hundreds and
sometimes thousands of kilometres. No sunlight reaches
these dark depths. Here and
there huge mountains rise up
from the sea bed. They are
called seamounts and are old
volcanoes with their peaks
far below the surface of the
ocean.
Less than 50 years ago,
scientists discovered the
longest mountain range in
Illustration: Cobus Prinsloo
Oceans and
seas are
great areas
of salt water
that cover
more than
two-thirds
of the total
surface
of planet
Earth. Seas
are much
smaller and
shallower
than oceans
and are usually partly
surrounded
by land.
25
Arctic Ocean
North
Sea
Pacific
Ocean
North
Atlantic
Ocean
Carribean Sea
Baltic Sea
Black Sea
Persian Gulf
Mediterranean
Sea Red Sea
Arabian Sea
Pacific
Ocean
Indian
Ocean
South
Atlantic
Ocean
Antarctic Ocean
the world. It stretches for
some 65 000 kilometres
through the middle of the
world’s oceans. The mountains are called mid-ocean
ridges. Down the middle
of these ridges run deep
grooves, called rift valleys.
Ocean currents
The waters nearer the
poles are icy cold. They mix
together with the warmer
waters nearer the equator,
moving around to create
ocean currents. How does
this happen? Warmer water
from the oceans around the
equator rises to the top,
while colder
water from
the oceans
around the
26
poles sinks to the bottom.
This cold water moves along
the ocean bed towards the
warm tropics, while the
warm water from the tropics
is pushed back to the poles
at the surface. The water
moves round and round.
Ocean currents are therefore
caused by the rising and sinking of warmer and colder
water.
Waves
Waves are made by the
wind blowing across the surface of the ocean. The wind
pushes the water upwards,
making a wave crest. Gravity
pulls it back down again,
into a wave trough. See
for yourself how waves
are formed by blowing air
through a straw across some
water in a shallow pan.
Sometimes, in the top
500 metres of water, the
wind drives rivers of moving
water for thousands of kilometres. In the open ocean
water moves in great circles
that are called gyres. In the
northern hemisphere, gyres
circulate clockwise, while
in the southern hemisphere
they circulate anti-clockwise.
These currents have a huge
influence on the weather.
Are our oceans
healthy?
It is important to us that
the oceans stay healthy,
because:
• They drive our climate
and weather;
• They provide a liveli-
Let’s see for ourselves how warm and cold water can cause ocean currents.
r
taine
r con
o
r
e
ch
)
• Pit water
color
p
a
T
(dark
•
e
y
d
od
• Fo ube tray ing
c
k
c
I
• e r glass ba
a
e
l
C
•
dish
1. Mix the food dye into the
water, pour the water into an
ice cube tray, and freeze it.
2. Fill the glass baking dish
with warm tap water to represent the warm water near
the equator.
3. Place one ice cube at
each end of the baking
dish, representing the
cold water near the poles.
What do you think will happen as the ice
cubes melt? See how the cold (colored) water sinks
and moves along the bottom of the baking dish
toward the warmer water in the middle. The warmer
water moves toward the ends of the baking dish; as
the cold water begins to warm,
it begins to rise. Can you explan
how differences in water temperature in different parts of
the “world ocean” cause ocean
currents?
27
activities;
• The oceans pose
threats through floods (e.g.
the tsunami (tidal wave) in
December 2004 in Asia),
storms, sea level change and
coastal erosion. More than
half the world’s population
lives near the sea.
Oceans are used for waste
disposal. Most waste eventually ends up in the oceans,
ILLUSTRATION: COBUS PRINSLOO
Mapping the ocean floor
For many years scientists
knew more about the surface of the Moon than about
the ocean floor. In recent
years, however, they have made much progress with mapping the ocean floor, using sonar detectors. Sonar stands
for Sound Navigation and Ranging. Sonar detectors send
out pulses of sound. When the pulses hit the ocean floor,
they send back echoes. The pattern of the echoes gives a
picture of what the ocean floor looks like, showing features
like seamounts and trenches.
The time echoes take to return tells scientists how deep
the ocean floor is. Sonar is also used to find shipwrecks
and shoals of fish. Sonar was invented in 1915 by
Professor Langevin in France to detect icebergs following
the sinking of the passenger ship, the Titanic, by an iceberg in 1912.
hood for many millions of
people worldwide through
fishing, the exploitation of
energy and mineral resources, shipping, and leisure
28
with the result that marine
pollution is a global problem
- every part of every ocean is
now affected. But the most
critical threats are to shal-
low seas and shorelines
near highly-populated areas.
Threats to oceans
The role
of science
Oceanographic
research has gathered
a huge store of
knowledge on the
physics, chemistry and
biology of the oceans
since the 19th century.
Current work is now
combining separate
pools of information
to help us understand
how the living and
non-living elements of
the marine environment interact, and
how the atmosphere
interacts with the
oceans.
Some scientists think that
climate change, perhaps
helped on by human activities, will cause major changes in ocean currents. We
cannot yet say what these
changes or their implications
will be.
Some idea of the economic disruption which could be
caused is shown by El Niño,
a frequently occurring, natural phenomenon in which
an ocean current suddenly
switches off. In the 1997/98
event droughts, forest fires
and air pollution were severe
in some parts while floods
and storms devastated other
areas. Fisheries and agriculture were affected across the
globe.
All over the world, the sea
level is currently rising at 12 centimetres every ten years
as the oceans warm and
expand. Scientists predict
that this increase will double
in the next century. It will
have greater effects where
land is naturally sinking, or
where human activities have
damaged coastal protection.
Fisheries
Most of the world’s sea
fisheries are over-exploited.
Excessive fishing effort leads
to the collapse of stocks and
affects the ecological balance
for all marine organisms.
Certain fishing techniques
such as bottom trawling and
dredging damage the sea
bed and coral reefs. Other
methods such as gill-nets
catch large numbers of nontarget species including
marine mammals, turtles and
seabirds.
Oil spills from tankers cause
acute pollution to coastal communities and chronic pollution
to the marine environment
generally. (Photograph: Marine
and Coastal Management,
Department of Environmental
Affairs and Tourism)
29