What’s the central dogma of biology?

A. DNA RNA ProteinB. DNA Protein GeneC. DNA Keratin HairD. DNA RNA Amino Acid

What’s the 1st step of protein synthesis?

A. ProteinB. TranscriptionC. TranslationD. DNA

Where does transcription take place in the cell?

A. CytoplasmB. RibosomeC. NucleusD. Cell Membrane

From Gene to Protein

• Genes are DNA sequences that hold the instructions to build a protein.– For example, there’s a gene that

codes for a protein called keratin.

Keratin is the protein that makes our hair & nails.

Protein SynthesisDNA RNA Protein

• Protein synthesis (making proteins from your genes) occurs in 2 steps:– Transcription– Translation

Where we left off…

• We’ve completed the 1st step of protein synthesis (transcription)… now what?

TRANSLATION

• We’ve created an mRNA copy of the gene.

• The mRNA has left the nucleus & is headed to the cytoplasm.

Protein Synthesis - Translation

Translation

• The mRNA made during transcription is used to make a protein.– DNA mRNA Protein

Remember!

• Proteins (sometimes called polypeptides) are macromolecules made of monomers called amino acids.

So, to build a protein, we need to link together amino acids.

Translation – Step 1

• The mRNA molecule (made during transcription) attaches to a ribosome in the cytoplasm.

Translation – Step 2

• The mRNA is broken down into sets of 3 nucleotides, or codons.

• The nucleotides are read in “words” made of 3 nucleotide “letters”.

• Each “word” is called a codon & contains the genetic code for 1 amino acid.

Each codon on an mRNA sequence codes for a specific amino acid.

Translation – Step 3

• As each codon of the mRNA moves through the ribosome, the correct amino acid is brought to the ribosome by tRNA.

• Each tRNA molecule has a group of 3 nucleotides called the anticodon & an amino acid attached.– The anticodons pair with the codons.

In order for the tRNA to attach the amino acid, it needs to bind to the mRNA sequence using its anticodon.

The anticodon is complementary to the codon!

The first “word”, or start codon, is always the same for every protein. It is always AUG.

Methionine

Using the genetic code wheel, you can figure out which amino acid a codon represents. Which amino acid is associated with the start codon AUG?

Move from the inside out!

There are a total of 20 different amino acids that can be arranged in different ways to make different proteins.

Translation – Step 4

• The ribosome transfers the amino acid from the tRNA to the polypeptide chain being formed in a process called elongation.– This forms a peptide bond

between the amino acids, which is why proteins are called polypeptides.

Translation – Step 5

• The empty tRNA molecule exits the ribosome & is recycled by the cell & can bind another amino acid.

Translation – Step 6

• The ribosome continues to match codons in the mRNA with anticodons in tRNA until it reads a codon that says “stop.” When this happens, the ribosome releases the mRNA & the protein.

Could you give me the amino acid sequence of this gene?

CACGTAGACTGAGGACTC

GUGCAUCUGACUCCUGAG

GUG-CAU-CUG-ACU-CCU-GAG

Val-His-Leu-Thr-Pro-Glu

1. DNA

2. Make mRNA

3. Separate mRNA into codons

4. Use codon chart to find amino acids