DNA to RNA to ProteinsPart II

RNA to Proteins:Making Proteins

* Be sure to watch Part I about messenger RNA before continuing with Part II: Making Proteins.

Now that the mRNA has successfully made a copy of the DNA’s instructions, it is ready to leave the nucleus – remember mRNA has permission as the “messenger” to leave while the DNA does not.

C

C

U

U

Original DNA

A

mRNA copy

A

AG

T

CG

C

A T

T

Now that the mRNA has left the nucleus it is ready to combine with a ribosome and “transfer” RNA (tRNA) to make proteins.

CC UU A mRNA copy

Ribosome

A G G

tRNA

Amino Acid

The ribosome reads the mRNA message and then looks for the “transfer” RNA (tRNA) carrying the correct message. Which tRNA is carrying the correct message - #1 or #2?

CC UU A

mRNA

A G G

tRNA #2

Amino Acid

C G G

tRNA #1

Amino Acid

Ribosome

A G G

tRNA #2

Amino Acid

Answer = tRNA #2 When the ribosome finds the correct tRNA message, they combine.

CC UU A

mRNARibosome

U A A

tRNA

Amino Acid

A G G

tRNA

Amino Acid

This process then repeats itself. The ribosome moves to the right and reads the next 3 bases. The correct tRNA matches up and brings the next amino acid. The first amino acid then sticks to the first one.

CC UU A

Ribosome

U

U A A

tRNA

Amino Acid

A G G

tRNA

Amino Acid

This process happens over and over again. Once the whole mRNA message has been read, the amino acid “chain” is released and becomes a protein.

CC UU A

Ribosome

U