Biggest Ever Maths and Science Lesson
Investigating DNA
Attempt to break the GUINNESS WORLD RECORD
3 November 2015
This is a very
special lesson
because thousands
of classes around
the world
are sharing this
same lesson today.
Image thanks to Dr John Molot, Environmental Medicine
DNA is what makes you a very special human
being, different from every other living thing.
You have identical copies of the same DNA in
every cell in your body and your DNA is
different from any other DNA.
DNA carries the message which made you
grow from a single cell into the person you
are now. For the whole of your life DNA
controls how your body works and grows
and changes.
In this lesson we
find out what
DNA is, how it
carries the
messages that
control all living
things and how it
copies itself.
www.news.bbc.co.uk/hi/english/static/in_depth/
sci_tech/2000/human_genome/default.stm
THE SHAPE OF DNA
DNA is like a twisted ladder.
Each step of the ladder is made up of
two bases.
There are only four types of base A, T,
C and G: base A always pairs with T,
and C always pairs with G.
The chemical names for these bases
are adenine (A), thymine (T),
cytosine (C) and guanine (G).
This shape is
called a
double helix.
The DNA genetic code is a sequence of the
letters A,T, C and G in different orders, with
many repetitions, for example:
and on and on and on …
Our entire DNA sequence is called a
genome.
The human genome
in your DNA gives the
biological instructions
needed to make you.
The human genome
has about 3 thousand
million base pairs.
Image from Scientific American
If all the DNA in your body were connected it
would stretch over 1200 million kilometres
(744 million miles)! That’s 1500 return trips
to the moon, or 4 return trips to the sun.
And all this DNA fits inside you!
DNA and CHROMOSOMES
The nucleus in each
cell in the human
body contains 2
metres (6 feet) of
DNA. The cell is very
small, and as there is
so much DNA, it must
be tightly packed into
packages that are
called chromosomes.
Our DNA determines all our characteristics, for
example our sex, the colour of our skin, hair and
eyes, our height, if we have freckles or not, if we
can roll our tongues, if we are likely to get certain
diseases … etc.
A distinct sequence of the
letters that determines one
characteristic is called a gene.
Humans have about 20,000
genes on 46 chromosomes,
23 inherited from each
parent.
https://www.youtube.com/watch?v=TmTI9oFHv3E
In 1953 Francis Crick and James Watson discovered the
double helix structure of DNA. Rosalind Franklin’s X-ray
studies of DNA gave them the clue to this structure.
Rosalind Franklin died in 1958. She was not awarded the
Nobel Prize that went to the other three scientists in 1962.
The study of the human genome is
crucially important to modern
medicine, in understanding disease,
and in trying to find new treatments.
A rough draft of the human genome (the complete
DNA sequence) was completed in the year 2000. The
final map of the human genome was completed by
many scientists and mathematicians in 2003.
There are an estimated 20,000 to 25,000 genes in our
genome and there is still a lot more to find out about
them.
Gene switches are what really make humans tick
Our bodies have many
different types of cells
that differ because
some genes are
switched on and some
are switched off in
each cell.
Some genes are only
switched on during the
development of a baby.
After birth their job has
been completed and
they are switched off.
All living things have DNA. Parts of the DNA of any two different
species may be the same but other parts will be different.
Here are some examples of small parts of the DNA of different
species.
DNA is made of
chemical building
blocks called
nucleotides.
To form a strand
of DNA,
nucleotides are
linked into chains.
Pairs of nucleotides link together to form DNA.
As cells divide, DNA divides to form 2 exact copies of
itself so that each new cell has a copy of the DNA.
CELL REPRODUCTION
The nucleotides in the DNA separate, and new
nucleotides that are floating in the nucleus of the cell
join onto the two parts to make two exact copies of the
DNA. As the DNA splits lengthwise the nucleus itself
splits into two, replacing the original cell by two new
cells that are exact copies of the original cell.
Paper Origami
Pipecleaners
Sweets and
Toothpicks
There are many ways to make DNA models.
Now it is your turn to make your own.
Have fun! Download free resources from
www.bubblymaths.co.uk/dna-lesson-resources