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. Separation of the two strands of the DNA double helix. 2. After the two strands are separated, new matching DNA strand is

formed one base at a time for each of the old DNA strands.3. The result is two identical DNA double helixes.

Understanding the DNA Language

DNA splits apartNew DNA strands form on the two separated

strands

There are now two copies of the

DNA

From Gene to Protein: DNA with subtitlesThe 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)

Free amino acids

Russian Ribosome (translator and

factory)

Final protein made of

amino acids

English

ActivityLet’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 6) Protein

7) Doctor

Roles:1) DNA – you are in charge of splitting the DNA open so that the

messenger RNA can copy the genes.2) 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.

3) Cytoplasm 1 (nucleus) – you are in charge of supplying the bases to the mRNA so that it can copy the genes in the DNA

4) Ribosome – you are in charge of taking the mRNA and building the amino acids from the mRNA’s sequence.

5) 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.

6) Protein – you are in charge of taking the amino acid chain from the ribosome and finding what protein it is producing

7) Doctor – you are in charge of taking the protein and finding out if there is anything wrong with the proteins the DNA is making.

G C

A U

(U in place of T)

Base matching

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

Things you’ll need:

mRNA

Ribosome

AA C

DNA

C A

Gene 1Gene 2

TT T

TGG

G

GC

CAU

A AA

GC

U U

mRNA 2 mRNA 1

GCC A

UA A

AG

CUU

Threonine amino acid amino acid

amino acid amino acid

Protein 2 Protein 1

Transcription

Translation

ribosome