Download Modeling Activity: How Genes Make Proteins…

Modeling Activity: How Genes Make Proteins…
I. DNA Replication
Base Pairing Rules for DNA Replication:
________________ ↔ ________________
________________ ↔ ________________
1. When does DNA replication take place during the cell cycle?
2. Using the base cards provided, randomly place 8 nitrogen bases in a row in front of you. Practice
simulation of DNA replication. Once you have a complete two strand DNA molecule, write the
parent and complementary DNA strand in your lab book.
II. Protein Synthesis
There are two steps in protein synthesis: transcription and translation. Transcription is when RNA
polymerase transcribes a single strand of DNA into a RNA molecule. Translation is when mRNA is
translated into a sequence of amino acids that will create a protein that will be used by the organism.
Modeling Transcription: Record information and diagram process in your lab book.
Base Pairing Rules for Transcription (DNA  mRNA):
________________ ↔ ________________
________________ → ________________
________________ → ________________
1.
2.
3.
4.
Using yarn, create a nucleus at your work station.
Using the orange DNA cards, place the “TAC” card in the nucleus of the cell. This card will be
the first card in your DNA sequence.
Place all other orange DNA cards except for the “ATC” card in a random order in a row to
the right of the “TAC” card. Add the “ATC” card to the end of your DNA sequence. Fill in
Table 1 with the appropriate sequence of DNA
Transcribe the DNA sequence into an mRNA molecule using the yellow mRNA cards to the
appropriate DNA cards. Remember, each 3 letter sequence card is called a codon and codes
for a specific amino acid. Fill in Table 1 with the appropriate mRNA sequence from the
transcription.
Table 1: Protein Synthesis – From DNA to Amino Acid (AA) Sequences
DNA
TAC
mRNA
AUG
Amino
Acid
Met/
Start
tRNA
UAC
Modeling Translation: Record information and diagram process in your lab book.
Base Pairing Rules for Translation (mRNA  tRNA):
________________ ↔ ________________
________________ ↔ ________________
1. Move the single strand mRNA molecule outside of the cell nucleus and into the cytoplasm of the
cell. You may put away the DNA cards and the yarn from the cell nucleus.
2. Determine which amino acid matches up with each mRNA codon using the codon chart. Fill in
Table 1 with the appropriate amino acid sequence from the translation of mRNA into amino
acids.
3. Determine the correct sequence of anticodons using the green tRNA cards. tRNA anticodons are
complementary to the mRNA and like RNA they use uracil instead of thymine. The green tRNA
cards should be placed above the mRNA codon cards. Fill in Table 1 with the appropriate
anticodon sequence for the tRNA.
4. Now place, the appropriate red amino acid cards above the tRNA anticodons.
5. As each tRNA anticodon finds its corresponding codon on the mRNA strand, the tRNA will
detach from its amino acid. The amino acids will remain at the ribosome and form a peptide
bond with the next amino acid brought by another tRNA. Two or more amino acids bonded
together are called a polypeptide. Translation is complete when a codon of mRNA codes for an
“end” indicated on the codon chart.
III. Postlab Questions
1. What are the three parts of a nucleotide of RNA? Be specific.
2. What are three ways in which DNA differs from RNA?
3. What are the end products of transcription and translation?
4. Do transcription and translation take place in the same spot in a eukaryotic cell? Justify your
answer.
5. Do transcription and translation take place in the same location of a prokaryotic cell and
eukaryotic cell? Justify your answer.
6. What is the central dogma concept for protein synthesis?
7. What bond connects amino acids in a polypeptide chain?
8. Given below is an imaginary sequence of DNA. Fill in the missing boxes in the chart by writing
the correct mRNA codons, amino acids, and tRNA anticodons.
DNA
TAC
mRNA
AUG
Amino
Acid
Met/
Start
tRNA
UAC
AGG
GGC
CTC
TTA
CAG
GAT
CCG
ATC