1. Protein Synthesis

2. Protein Synthesis
So how do the genes in our DNA influence our characteristics?
Each chromosome contains a long molecule of DNA, and this molecule of DNA contains many genes
A gene is a segment of the DNA molecule that has a specific sequence of nucleotide bases (A, T, C, G)
The nucleotide bases determines the specific sequence of amino acids that will be joined together to form a protein
In other words, amino acids make up proteins

3. Protein Synthesis Proteins determine our characteristics
For example, one gene gives the instructions for making the pigment melanin, a molecule that contributes to skin and hair color
Proteins are made in the ribosomes in a two-step process: Transcription & Translation

4. Protein Synthesis - transcription
Transcription uses the information in a gene to make a messenger RNA molecule, called mRNA
RNA has a structure like DNA, but it has two main differences from DNA
Single-stranded
Has uracil (U) instead of thymine (T); so the letters for RNA are A, G, U, C
During transcription, and enzyme separates the two strands of DNA and makes the mRNA molecule by adding RNA nucleotides, one at a time
Each DNA nucleotide in the gene is matched by a complementary mRNA nucleotide: C with G, and A with U (instead of T)

5. Protein Synthesis - transcription

6. Protein Synthesis - Translation
During Translation, each set of 3 nucleotides in an mRNA molecule codes for one amino acid in a protein
A set of 3 nucleotides is called a codon
Each codon specifies a particular amino acid
But how are the right amino acids added in the right sequence to match the sequence of codons in the mRNA?
A special type of RNA, called transfer RNA (tRNA), is needed to make sure that the correct amino acid is brought to match each codon in the mRNA within the growing protein molecules

7. Protein Synthesis - Translation

8. Protein Synthesis – The Steps
DNA
(given)
mRNA
(codons)
(no T!)
tRNA
(anti-codons to match up with mRNA’s codons)
Amino Acid
(use Codon Chart to find amino acid based on mRNA)

9. Codon Chart – Based on mRNA codons
Start Codon – AUG (codes for the amino acid methionine/met)
Signals the start of a gene
Stop Codons – UAA , UAG, UGA
Signals the end of a gene