1. Protein Synthesis
DNA RNA Protein

2. How is the code in DNA Used to Make Proteins?
Using RNA (Ribonucleic Acid)!
RNA is similar to DNA (they are
both nucleic acids, and both are
made up of nucleotides) but RNA has 3 significant differences:
It is Single stranded (instead of
double stranded like DNA)
It has the sugar ribose (instead
of deoxyribose like DNA)
It contains the base Uracil (U) instead of Thymine

3. 3 Types of RNA
mRNA is Messenger RNA – made from a section of DNA (a gene) in the nucleus (carries DNA’s “message”)
tRNA is transfer RNA – responsible for transferring amino acids to a ribosome to make a protein in the
cytoplasm
rRNA isRibosomal RNA – makes up ribosomes
that help assemble
proteins

4. Transcription: an mRNA COPY of a DNA section (gene) is made in the nucleus
DNA mRNA
Enzymes “unzip” a section of DNA
Complementary RNA nucleotides pair with DNA nucleotides and bond together (AUCG) to make a SINGLE strand of mRNA based on the DNA code
The mRNA strand breaks away from the DNA and takes the DNA “message” from the nucleus to the cytoplasm

5. DNA mRNA = Transcription
Enzymes “read” the
DNA bases in a gene
and put together a
complementary,
single-stranded mRNA
molecule based on the
DNA code
Example:
DNA sequence: TAC CCA TGC CTG
mRNA sequence: AUG GGU ACG GAC
Remember, NO THYMINE in RNA!

6. Translation: the code in mRNA is TRANSLATED into a sequence of amino acids – a protein
mRNA travels out of the nucleus to a ribosome in the cytoplasm
The ribosome holds the mRNA in place
tRNA brings amino acids to the ribosome
The nucleotides on mRNA are divided into groups of 3 (“triplets”)
Each set of 3 nucleotides on mRNA is called a CODON
One codon is the “code” for one
amino acid
Codons on mRNA match up with
anticodons on tRNA for specific amino acids
Each tRNA delivers one amino acid
The amino acids are attached (bonded) together to make a
protein (they are attached together
based on the original sequence in
the DNA molecule that mRNA was made from!)
RNA Protein

7. Codons and Anticodons
Codon - a group of 3 bases in mRNA (that “code” for ONE amino acid) *There are 20 different amino acids Anticodon – a group of 3 bases in tRNA (that are complementary to a codon in mRNA)

8. “Decoding” the message – the Genetic Code (based on codons in mRNA)
How do mRNA, tRNA and the ribosomes know which amino acids to put into the protein?
THE GENETIC CODE!
Based on codons (triplets) in mRNA
Universal to ALL LIFE!!!

9. Transcription and Translation

10. The Protein
Each protein is a chain of amino acids that has a specific job
The structure (shape) of the protein depends on the sequence of amino acids and the folding of the protein

11. Transcribe and Translate!
DNA: TAC ACT GGC TAA CGT TCC AGT ACC AAT GCG ATT mRNA: ________________________________________ tRNA: _________________________________________ amino acids: _____________________________________ DNA: TAC ATC GTC TCG CCT AGT CCT GAA CTG CCA ACT mRNA: _________________________________________ tRNA: __________________________________________

12. Mutations Mutation = a change in DNA (genetic material)
Mutations can change ONE single base pair (point mutations) or they can change long sequences of DNA/ chromosomes
IF mutations occur in gametes, they can be passed on to offspring!
IF the bases in DNA are changed, the mutation is copied into mRNA during
transcription,
and then put
into the amino
acids/ protein
during
translation (this
usually means
the protein doesn’t “work” properly, if at all)

13. Mutations Original DNA: TAC CTT CAG GCG Original mRNA: AUG UGG GUC CGC
Original Amino Acids: Met - Glu - Val - Arg
Mutated DNA: TAC CAT CAG GCG
Mutated mRNA: AUG UGA GUC CGC
Mutated Amino Acids: Met – Val – Val - Arg
Example: Sickle cell anemia (CTT in DNA is
changed to CAT, changing one amino acid
in the protein)- red blood cells are sickle-
shaped instead of round and do not carry
oxygen as well

14. Label the Diagram Nucleus DNA mRNA Transcription cytoplasm tRNA
Ribosome
Amino acid
Protein
Codon
anticodon
translation

15. Complete the Following Table
DNA Sequence
AAC TAG GGT
Explain how DNA is transcribed.
mRNA codons
What does the ‘m’ mean in mRNA? Explain why.
tRNA anti-codons
Explain how the mRNA code is translated into amino acids.
Amino acid sequence
Describe how a protein is formed and identify 3 roles of proteins.