3.6: Protein Synthesis Pizza (Worksheet)

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Background

Proteins are complex chemicals made up of different amino acids, of which there are a total of 20 types. Different combinations of amino acids produce different proteins. The process of making a protein is called protein synthesis, and involves two major steps: (1) transcription and (2) translation.

In transcription, a DNA strand in the nucleus forms the template for the creation of single-stranded messenger RNA (mRNA). Transcription occurs when an enzyme called polymerase strings together free-floating RNA nucleotide bases that are complementary to the exposed strand of DNA.

For translation, the mRNA strand leaves the nucleus for the cytoplasm. There, a ribosome translates the mRNA strand. Ribosomes read three nucleotides of the mRNA at a time (called a codon) and, with the help of single-stranded transfer RNA (tRNA), matches the codon to the corresponding amino acid. This amino acid is added to the growing protein chain. When a ‘stop’ codon is read, the protein is complete. As the amino acid chain exits the ribosome, it folds into its unique shape, and can go to work in the body.

Part 1: From DNA to Amino Acids

This activity breaks down protein synthesis using the metaphor of PIZZA!

*Warning: this activity may make you hungry!*

Use your Amino Acids Reference Sheet to complete the following table. Fill in the blank spaces of each row with either the missing DNA triplet, the mRNA codon, or the Amino Acid. While there are actually multiple codons that code for any one amino acid, for this activity there only needs to be one DNA triplet and one corresponding mRNA codon recorded for each amino acid.

Remember: RNA uses uracil (U) instead of thymine (T)!

DNA	mRNA codon	Amino Acid
TTG	AAC	Asparagine
GGG		Proline
	UAU	Tyrosine
	CAC	Histidine
CGT	GCA
AAA
TTT	AAA
CAA

As you fill in the chart, you will learn how to transcribe the nucleotide bases of DNA (the As, Ts, Gs, and Cs) into mRNA using the “language” of RNA (which replaces any ‘T’ with a ‘U’). As you continue to fill in the chart you may find that you can transcribe the triplets by yourself, using your knowledge of base pairings, without using the amino acids chart at all!

Part 2: Decoding a Protein Pizza

Your instructor will give you a DNA “pizza recipe” in DNA base triplets. Use your knowledge of transcription and translation to figure out what kind of pizza you have!

1. Write down the DNA pizza recipe in the DNA section of the chart, three letters at a time, going vertically down the chart in the far left column.
2. Transcribe each DNA triplet in the pizza recipe into a mRNA codon.
3. Once each triplet has been transcribed into mRNA, you can begin to translate the mRNA code to construct your pizza. Use the Pizza Ingredients List to decode what ingredients are in your pizza. The ingredients in the chart are in mRNA, so refer to your mRNA codons in the second column.
4. Use your Amino Acids Reference Sheet to figure out which amino acid corresponds to each mRNA codon. In this case you are doing the work of the ribosome: matching the mRNA codon to the specific amino acid that is needed for the growing protein chain. Just like all of the ingredients together make a tasty pizza, so too does each amino acid play an important role in making up a larger protein!

DNA Pizza Recipe Code Write the recipe in this column, 3 nucleotides at a time.	mRNA Codon Transcribe the DNA code into the corresponding mRNA codon	Pizza ingredient Record the corresponding pizza ingredient, according to the ingredients chart (Use the mRNA codon to look it up.)	Amino Acid Record the corresponding amino acid (for a protein) using your amino acid chart!
Example: AAA	Example: UUU	Example: Stuffed crust	Example: Phenylalanine

Part 3: Reflection

Did your pizza have any ingredients that you would not usually find on a pizza? Just like one ingredient can make a pizza unique, so too can one new or different amino acid create a protein that is different from the protein that was supposed to be synthesized. DNA mutations that change, move, or delete a letter in the original DNA triplet can, through protein synthesis, result in the creation of different and new proteins in the body.

A protein that differs from the original protein that was supposed to be produced can sometimes be a good thing for an organism. If the protein results in a new functioning that gives the

organism an advantage in its environment then the “incorrect” protein would be beneficial, helping the organism achieve reproductive success. That protein could be selected for through the process of natural selection. In that case, the “incorrect” protein would increase in frequency in the population, and become the more common protein over time (and no longer be considered “incorrect”).

Amino Acids Reference Sheet

The 20 Amino Acids in Human Proteins and How They Are Coded For

Cells in the human body use information in the genetic code to directly encode 20 amino acids. The table below displays how this is done. First, a DNA base triplet is copied to create mRNA in the language of RNA. The mRNA then travels to the cytoplasm, where the ribosome reads each mRNA codon to assemble the corresponding amino acids into a growing protein chain. The “stop” codon is the last triplet in the process. It tells the ribosome that the process of making that specific protein is complete.

This table lists DNA base triplets and their corresponding mRNA codons that the ribosome reads to attach each specific amino acid. Some amino acids can be made more than one way.

Amino acids that can be made one way:

Amino Acid	DNA base triplet	mRNA codon
Methionine	TAC	AUG
Tryptophan	ACC	UGG

Amino acids that can be made two ways:

Amino Acid	DNA base triplet	mRNA codon
Asparagine	TTA or TTG	AAU; AAC
Aspartate	CTA or CTG	GAU; GAC
Cysteine	ACA or ACG	UGU; UGC
Glutamate	CTT or CTC	GAA; GAG
Glutamine	GTT or GTC	CAA; CAG
Histidine	GTA or GTG	CAU; CAC
Lysine	TTT or TTC	AAA; AAG
Phenylalanine	AAA or AAG	UUU; UUC
Tyrosine	ATA or ATG	UAU; UAC

Amino acids that can be made three ways:

Amino Acid	DNA base triplet	mRNA codon
STOP codon	AAT or ATC or ACT	UAA; UAG; UGA
Isoleucine	TAA or TAG or TAT	AUU; AUC; AUA

Amino acids that can be made four ways:

Amino Acid	DNA base triplet	mRNA codon
Alanine	CGA or CGG or CGT or CGC	GCU; GCC; GCA; GCG
Glycine	CCA or CCG or CCT or CCC	GGU; GGC; GGA; GGG
Proline	GGA or GGG or GGT or GGC	CCU; CCC; CCA; CCG
Threonine	TGA or TGG or TGT or TGC	ACU; ACC; ACA; ACG
Valine	CAA or CAG or CAT or CAC	GUU; GUC; GUA; GUG

Amino acids that can be made six ways:

Amino Acid	DNA base triplet	mRNA codon
Arginine	GCA or GCG or GCT or GCC or TCT or TCC	CGU; CGC; CGA; CGG; AGA; AGG
Leucine	AAT or AAC or GAA or GAG or GAT or GAC	UUA; UUG; CUU; CUC; CUA; CUG
Serine	AGA or AGG or AGT or AGC or TCA or TCG	UCU; UCC; UCA; UCG; AGU; AGC

Pizza Ingredients

Important: All ingredients are based on the mRNA code!

Basics: GCA - Thick crust GUA - Thin crust UUU - Stuffed crust	Acidics: CUA - Marinara sauce CUG - Barbecue sauce CUU - White sauce UUA - Garlic sauce
Aromatics: AAA - Pepperoni AAG - Sausage ACC - Chicken AUA - Bacon AUG - Pineapple	Hydroxylics: AGA - Mozzarella cheese UGU - Extra cheese (mozzarella)
Aliphatics: AAU - Red onion CAA - Black olives CCA - Animal crackers CGA - Spinach GAU - Mushrooms GGA - Lettuce GUU - Artichoke hearts	Stop codons: UAA - Stop codon UAG - Stop codon UGA - Stop codon

*Remember: All ingredients are based on the mRNA code!

Build Your Own Protein Pizza

Choose from the ingredients list to make your own pizza! Remember: because the ingredients are in mRNA, you have to fill in the chart working right to left from the Pizza Ingredient. Amino acids can be looked up at the end.

DNA Pizza Recipe Codons	mRNA Codon	Pizza Ingredient	Amino Acid
(write the recipe in this column, 3 letters at a time)	(Once the DNA triplet is transcribed into mRNA, you can find the pizza ingredient)	What pizza ingredient is this, according to the ingredients chart? (Remember: the ingredients in the chart are in mRNA!)	Once you have completed the activity, look up what amino acid this ingredient corresponds to in real life!
Example: TCT	Example: AGA	Example: Mozzarella cheese	Example: Arginine

Extra Practice: Go From RNA to DNA

Work backwards from the RNA strand to find the original DNA base triplet! Remember: RNA uses U (not T). So every time you see ‘U’ in the RNA strand, treat it just like ‘T’ to find the complementary nucleotide base!

DNA	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _
RNA	UUU	AUG	CUG	CUU	UUA	GAU	CAA	UGU	UAA

DNA	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _
RNA	AAA	GUA	AUG	CUA	UUA	GUU	CGA	AAU	UAG

DNA	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _
RNA	GCA	AAG	UUA	GUU	UGU	CGA	CCA	AGA	UGA

DNA	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _
RNA	GCA	AUG	CGA	AGA	GAU	CUU	UUA	CUA	UAA

DNA	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _
RNA	ACC	CCA	AAU	GUA	GGA	CUU	UUA	GUU	UAG

DNA	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _	_ _ _
RNA	AUA	AGA	UGU	ACC	AAU	GAU	CUU	UUU	UGA

DNA Sequences to Provide Students

DNA	AAA	TAC	GAC	GAA	AAT	CTA	GTT	ACA	ATT

DNA	TTT	CAT	TAC	GAT	AAT	CAA	GCT	TTA	ATC

DNA	CGT	TTC	AAT	CAA	ACA	GCT	GGT	TCT	ACT

DNA	CGT	TAC	GCT	TCT	CTA	GAA	AAT	GAT	ATT

DNA	TGG	GGT	TTA	CAT	CCT	GAA	AAT	CAA	ATC

DNA	TAT	TCT	ACA	TGG	TTA	CTA	GAA	AAA	ACT

DNA	TTT	AAA	TTA	GTT	ACA	TCT	CAA	GAT	ATT

DNA	TAC	CAT	TCT	ACA	AAT	CAA	GCT	CTA	ATC

DNA	CGT	GAC	TTC	AAT	CTA	CCT	TTA	TCT	ACT

Answer Key (RNA & Protein)

UUU AUG CUG CUU UUA GAU CAA UGU UAA

Stuffed crust, pineapple, barbecue sauce, white sauce, garlic sauce, mushrooms, black olives, extra cheese, stop

AAA GUA AUG CUA UUA GUU CGA AAU UAG

Pepperoni, thin crust, pineapple, marinara sauce, garlic sauce, artichoke hearts, spinach, red onion, stop

GCA AAG UUA GUU UGU CGA CCA AGA UGA

Thick crust, sausage, garlic sauce, artichoke hearts, extra cheese, spinach, animal crackers, mozzarella cheese, stop

GCA AUG CGA AGA GAU CUU UUA CUA UAA

Thick crust, pineapple, spinach, mozzarella cheese, mushrooms, white sauce, garlic sauce, marinara sauce, stop

ACC CCA AAU GUA GGA CUU UUA GUU UAG

Thin crust, animal crackers, red onion, mushrooms, lettuce, white sauce, garlic sauce, artichoke hearts, stop

AUA AGA UGU ACC AAU GAU CUU UUU UGA

Bacon, mozzarella cheese, extra cheese, chicken, red onion, mushrooms, white sauce, stuffed crust, stop

AAA UUU AAU CAA UGU AGA GUU CUA UAA

Pepperoni, stuffed crust, red onion, black olives, extra cheese, mozzarella cheese, artichoke hearts, marinara sauce, stop

AUG GUA AGA UGU UUA GUU CGA GAU UAG

Pineapple, thin crust, mozzarella cheese, extra cheese, garlic sauce, artichoke hearts, spinach, mushrooms, stop

GCA CUG AAG UUA GAU GGA AAU AGA UGA

Thick crust, barbecue sauce, sausage, garlic sauce, mushrooms, lettuce, red onion, mozzarella cheese, stop