Question

Prelab Information
Purpose
Time
Question
Prediction
Explore the molecular process of building proteins from the information carried by RNA
using a laboratory procedure.
Approximately 45 minutes
How are proteins built using the information provided by a molecule of RNA?
RNA determines the sequence of amino acids in proteins and polypeptides by a two-
step process: transcription of DNA produces mRNA in the nucleus, then translation
of the mRNA to tRNA takes place at the ribosome in the cytoplasm.
Lab Procedure
Materials:
 helicase
 human cell


 tRNA sequence
 protein structure chart
Step 1: Transcribe the Information in DNA to mRNA
(The animation will zoom from the human cell to the nucleus to the DNA strand.)
a) Find and click the arrow that represents the direction in which the mRNA is built. Like DNA,
mRNA is always built from the 5' direction to the 3'.
b) Which RNA nucleotide can pair with the thymine (T) at the beginning of the strand? Drag it into
the DNA antisense strand to make a pair.
c) Complete nine (9) additional base pairs. Remember, there is no thymine (T) in RNA. The
adenine (A) in the DNA needs to pair with uracil (U).
d) After your mRNA sequence record is complete, click “Leave the Nucleus” to send the mRNA
to the ribosome in the cell’s cytoplasm, where production of proteins will take place.
Step 2: Locate Codons
(You will continue to read mRNA from the 5′ end toward the 3′ end.)
a) A codon is a sequence of three bases that indicates a unit of information in the RNA. A gene is a
series of codons that results in the production of a protein. Identify the codons of the mRNA
shown. The start codon for a gene is AUG, so start by dragging the blue start codon box over the
AUG on the strand. (The start codon is already recorded on the data table.)
b) Use the gray codon box to highlight additional codons three bases at a time. When you reach
a stop codon (either UAA, UAG, or UGA) you will need to use the pink stop codon box. As you
form codons, record them in Table 1.
Step 3: Translate mRNA
tRNA is composed of short sections of RNA that bond to the codons in mRNA. The screen shows a
pool of tRNA anticodons, which carry the amino acids to the ribosome and attach to the mRNA
when its sequence of base pairs is complementary with the mRNA in the ribosome.
a) For each codon, you will find the correct tRNA anticodon and drag it to the ribosome. Start with
the AUG codon in the ribosome. Find and drag its match, the UAC anticodon, to it. Record this

Student Guide (continued)
pair and the amino acid Met to complete the first row of Table 2.
b) Find the next anticodon you need to match the next mRNA codon you identified. Drag its
anticodon to the ribosome. Record in the second row of Table 2.
c) Remember, the ribosome can only handle two tRNA strands at a time. So, click the Dehydrate
button to activate the process of dehydration synthesis, or the loss of water molecules
during protein building.
d) Continue to build the protein by joining amino acids to the chain in the correct order. Every amino acid
joined to the protein results in the production of one more water molecule. Click Dehydrate to form the
peptide bonds. Watch the water molecule counter and be sure to record all data in your data Table 2.
When many amino acids are joined in sequence, this is a polypeptide chain.

Student Guide (continued)
Sequence and Protein Structure Chart


Student Guide (continued)
Data
Table 1: Codon sequences for mRNA molecule
Codons
AUG (start)

Student Guide (continued)
Data
Table 2: Translation of mRNA molecules
Codons
tRNA Anticodons
Amino Acid
Number of Water
Molecules
Produced
AUG (start)

how can I do this im so confused

Answer 1

You’re not alone — this lab just walks you through the three simple ideas: transcription (make mRNA), reading mRNA in codons, and translation (match tRNA anticodons to codons and use the protein chart). Here’s a short, clear step‑by‑step you can follow in the simulation, plus an example so you can see what to enter in Tables 1 and 2.

Quick rules to remember
- Base pairing DNA → RNA: A (DNA) pairs with U (RNA); T (DNA) pairs with A (RNA); G ↔ C.
- mRNA is always built 5′ → 3′. Read codons from the 5′ end toward the 3′ end.
- A codon = 3 bases. Start codon = AUG. Stop codons = UAA, UAG, UGA.
- tRNA anticodon pairs complementarily with the codon. In the simulation they give anticodons like UAC for AUG.
- Every peptide bond formed produces one water molecule. If n amino acids are joined into a chain, n − 1 peptide bonds (and n − 1 water molecules) are produced.

Step‑by‑step for the simulation
1. Transcription (make mRNA)
- Click the arrow that shows the mRNA direction (5′→3′).
- For each DNA base, drag the correct RNA base to pair: DNA T → RNA A; DNA A → RNA U; DNA G → RNA C; DNA C → RNA G.
- Complete the full mRNA strand and click “Leave the Nucleus.”

2. Find codons
- Starting at the 5′ end, place the blue start box over AUG.
- Move the gray codon box along the strand three bases at a time to mark each codon. Use the pink box when you hit a stop codon (UAA, UAG, UGA).
- Record each codon you find in Table 1 (first row is already AUG).

3. Translate (match tRNA and amino acids)
- For each codon, find the tRNA anticodon in the pool that is complementary to the codon and drag it to the ribosome. (Example: codon AUG → anticodon UAC.)
- Use the protein structure chart provided by your simulation to look up which amino acid each codon codes for (AUG = Met, etc.). Record the amino acid in Table 2.
- The ribosome holds two tRNAs at a time. Click “Dehydrate” to form the peptide bond and generate one water molecule each time you join a new amino acid. Record the water molecules produced each time (each peptide bond = 1 water).

Example (so you can see how to fill the tables)
Suppose your mRNA sequence (5′→3′) is: AUG GCU UUU UAA

Table 1 (codons)
- AUG (start)
- GCU
- UUU
- UAA (stop)

Table 2 (translation)
- Codon: AUG | tRNA anticodon: UAC | Amino acid: Met | Water molecules produced: 0 (start; no bond yet)
- Codon: GCU | tRNA anticodon: CGA | Amino acid: Ala | Water molecules produced: 1 (Met joined to Ala)
- Codon: UUU | tRNA anticodon: AAA | Amino acid: Phe | Water molecules produced: 1 (Ala joined to Phe)
- When you reach UAA, translation stops (do not add an amino acid)

Total water molecules produced for the whole polypeptide of 3 amino acids = 2 (n − 1 = 3 − 1).

If you want, paste the DNA or mRNA sequence you see in the simulation and I’ll fill Tables 1 and 2 for you step by step.