Download Slide 1

Understanding the DNA Language
Cells in our body are dividing all the time. For example, cell division in the lining of
your mouth provides the replacements for the cells that come off whenever you
chew food. Before a cell can divide, the cell must make a copy of all the DNA in
each chromosome; this process is called DNA replication. Why is DNA replication
necessary before each cell division?
1.
2.
3.
Separation of the two strands of the DNA double helix.
After the two strands are separated, new matching DNA strand is
formed one base at a time for each of the old DNA strands.
The result is two identical DNA double helixes.
DNA splits apart
New DNA strands form on
the two separated strands
There are now two
copies of the DNA
From Gene to Protein: DNA with subtitles
The instructions for making a protein are provided by a gene, which is a specific
segment of a DNA molecule, and proteins influence our characteristics.
For example, most of us have a protein enzyme that can create melanin, the
main pigment that gives color to our skin and hair. In contrast, albino people
make a defective version of this protein enzyme, so they are unable to make
melanin and they have very pale skin and hair.
What is a protein?
Problem: DNA and proteins have different languages. It’s like trying to build a shelf
but the instruction manual is in Russian. Luckily, there are steps our cells take
to translate the instructions in our DNA so that they can build proteins.
Modified from Serendip “From Gene to Protein - Transcription and Translation” Lesson April 2010
Each gene contains a specific sequence of bases. This sequence of
nucleotides gives the instructions for the specific sequence of amino acids that
should be joined together to form the protein.
A book divided into chapters:
1. The instructions in the gene in the DNA are copied into a messenger RNA
(mRNA) molecule. The sequence of bases in the gene determines the
sequence of bases in the mRNA. This step is called transcription.
DNA divided into
genes and
copied into a
messenger RNA
From “Russian” to “English”
2. The instructions in the messenger RNA are used by ribosomes to build the
correct amino acids in the correct sequence to form the protein coded for
by that gene. The sequence of bases in the mRNA determines the
sequence of amino acids in the protein. This step is called translation.
Messenger RNA
(mRNA)
Russian
Ribosome
(translator and
factory)
Final protein
made of
amino acids
Free amino
acids
Activity
Let’s act out how the DNA turns into all the proteins that make up our body.
You will need a person for each of these roles:
1)
DNA
3) Cytoplasm 1 (nucleus)
5) Cytoplasm 2 (cell)
2) Messenger RNA (mRNA)
4) Ribosome
7) Doctor
6) Protein
Roles:
1)
2)
3)
4)
5)
6)
7)
DNA – you are in charge of splitting the DNA open so that the
messenger RNA can copy the genes.
Messenger RNA (mRNA) – you are in charge of copying the genes on
DNA one base at a time. Each gene will end at a line so you’ll know
when to stop copying gene 1 and when gene 2 begins.
Cytoplasm 1 (nucleus) – you are in charge of supplying the bases to
the mRNA so that it can copy the genes in the DNA
Ribosome – you are in charge of taking the mRNA and building the
amino acids from the mRNA’s sequence.
Cytoplasm 2 – you are in charge of supplying the amino acids to the
ribosome so that it can build a protein from the mRNA sequence.
Protein – you are in charge of taking the amino acid chain from the
ribosome and finding what protein it is producing
Doctor – you are in charge of taking the protein and finding out if
there is anything wrong with the proteins the DNA is making.
Things you’ll need:
Ribosome
mRNA
Base matching
G
C
A
U
(U in place of T)
mRNA
translation
Amino acid
ACU
Amino acid 1
CAU
Amino acid 2
CCU
Amino acid 3
CUG
Amino acid 4
GAG
Amino acid 5
GUG
Amino acid 6
Protein 1
Protein 2
Translation
Threonine
amino acid
A
amino acid
amino acid
U
U U
G
A
amino acid
G
A
ribosome
mRNA 2
mRNA 1
Transcription
A A
T
T
G
U
A G
C
A
G
A
G T
G
T
Gene 1
Gene 2
DNA
U U
C
A A
A