Protein Synthesis (text version)

Transcription: Unzip DNA

Help Window:
The first step of protein synthesis is to "unzip," or separate, a section of the DNA molecule.

Select Unzip to divide the molecule.

Description:
Selecting the "Unzip" button causes a portion of the DNA molecule to split lengthwise.

What Happened Window:

In a real cell, the molecule unwinds from spools made of protein, then untwists. At this point the DNA resembles a ladder. Enzymes, special kinds of proteins, move up the ladder, breaking the rungs.

Transcription: Match bases to make mRNA strand

Drag and drop from well:
A
G
C
U

Help Window:
Like DNA, RNA is made up of four bases. Three of these bases, adenine (A), cytosine (C), and guanine (G), are the same as DNA. But instead of thymine (T), the fourth base is uracil (U). Each base has a complement -- another base that it can connect to. A complements U, and C complements G.

Drag bases from the left to their complementary bases on the DNA strand.

Description:
Nucleotides are dragged from one area of the screen to one side of the separated DNA.

What Happened Window:
The RNA molecule you've just transcribed consists of nine bases. In a real cell, the RNA molecule would be anywhere from 100 to 10,000 bases long.

An RNA molecule transcribed from DNA is called messenger RNA, or mRNA for short.The mRNA now moves away from the DNA and leaves the cell's nucleus. Outside the nucleus, ribosomes attach themselves to the RNA.

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Translation: Match tRNA anticodon to mRNA codon

Drag and drop from well:
UAC (methionine; compl. of AUG)
CCG (glycine; compl. of GGC)
AGG (serine; compl. of UCC)

Help Window:
Like DNA, mRNA consists of four bases. The bases in mRNA are grouped into sets of three called codons. Transfer RNA (tRNA) consists of the same four bases. Just as in the previous step, you want to find complementary bases. In this case, though, you need to find the complement of each codon.

Drag the appropriate tRNA from the bottom of the screen to the leftmost codon of the mRNA.

What Happened Window:
A ribosome has attached itself to the mRNA.Ribosomes are the cell's structures for building proteins.

The mRNA bases are grouped into sets of three, called codons. Each codon has a complementary set of bases, called an anticodon. Anticodons are a part of transfer RNA (tRNA) molecules. Attached to each tRNA molecule is an amino acid -- in this case, the amino acid is methionine (met). You've matched the first codon in this mRNA molecule, AUG, with its complement, UAC.

Description:
Ribosome moves to the right.

Translation: Match next codon

Drag and drop from well
UAC (methionine; compl. of AUG)
CCG (proline; compl. of GGC)
AGG (serine; compl. of UCC)

Help Window:
The ribosome has moved to the right and is now ready for a second tRNA.

Drag the appropriate tRNA to the next available codon on the mRNA molecule.

What Happened Window
The ribosome moved right, making space for the next tRNA. You matched the anticodon CCG with its complementary codon, GGC. The second tRNA brought the amino acid glycine, which binds to the methionine from the first tRNA.

The ribosome now moves right again. The first tRNA will float away from the ribosome, leaving its amino acid behind. It will pick up another methionine molecule, and wait until it is needed again.

Description:
Ribosome moves to the right. The two amino acids link, and the first anticodon moves away from ribosome.

Translation: Match next codon

Drag and drop from well
UAC (methionine; compl. of AUG)
CCG (proline; compl. of GGC)
AGG (serine; compl. of UCC)

Help Window:
The ribosome has moved to the right and is now ready for a third tRNA.

Drag the appropriate tRNA to the next available codon on the mRNA molecule.

Description:
Ribosome moves to the right, then disappears, leaving behind a polypeptide chain made up of three amino acids.

Well Done Window:
You've added another amino acid to the polytpeptide chain, the protein under construction. It is now three amino acids long. More and more will be added until the chain is 100 to 10,000 amino acids long. The protein synthesis will end when an stop codon is reached. The ribosome will then release the polypeptide chain.

DNA Replication

All Wound Up

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