Paper Transcription & Translation Student Instructions

NAME DATE Paper Transcription & Translation Student Instructions

Background Cells use the information in genes to build proteins. To do so, they first make an mRNA copy of the gene—a process called transcription. Then they decode the information in the mRNA to build a protein—a process called translation.

You will use a paper model to go through the processes of transcription and translation.

Prepare Your Materials • Cut out the DNA strips. Match the num- bered ends and tape them together. • Cut out the mRNA strips. Tape the ends together to form one long strand. • Cut out the Protein strip. • Cut out the Transcription Machine and the Translation Machine, then cut along the dotted lines.

TRANSCRIPTION Summary: A molecular machine (RNA Polymerase) attaches to a gene and makes a messenger RNA (mRNA) copy.

A cell does this: Do this with your model: 1. Transcription machin- Starting at the END, cut the ery “unzips” the DNA, DNA strip up the middle. After temporarily separating the you reach the circled base, Your DNA sequence may be different from the one pictured. complementary strands. stop cutting so that the DNA stays connected at the top. 2. RNA polymerase wraps Put the DNA template strand around the DNA template into the Transcription ma- strand. chine. Slide the Transcription machine to the circled base.

3. RNA polymerase Slide the mRNA strip into the attaches to the template Transcription machine. Line strand. It will read the up the ends of the DNA and DNA to build a comple- mRNA strands. mentary strand of mRNA. TIP: Tape or paper clip the mRNA onto the DNA strip.

A cell does this: Do this with your model: 4. RNA polymerase reads Starting with the circled DNA the DNA template strand, base, start writing the compli- adding building blocks to mentary bases on the mRNA the mRNA strand accord- strand (put one letter in each ing to the rules of comple- box). Don't shift the strands mentary base pairing: and lose your place! G (in DNA) pairs with C (in RNA); C pairs with G; T pairs with A; A pairs with U. 5. RNA Polymerase slides Write in the complementary along the DNA template bases, and slide the transcrip- strand, unzipping the DNA tion machinery as you go. and adding bases to the TIP: If you lose your place, go growing mRNA as it goes. back to the beginning and line up the first mRNA base with the circled DNA base. 6. Genes are typically Detach the transcription ma- thousands of bases long. chine, and set the DNA aside (you may trim any unused bit off the end of the mRNA). You have just transcribed a small piece of an actual gene!!

TRANSLATION Summary: The ribosome reads the bases of the mRNA, putting amino acids together to make a protein.

A cell does this: Do this with your model: 7. The mRNA attaches Starting at the beginning of to the Ribosome. The the mRNA strand, scan along ribosome slides along the until you find the first “AUG.” mRNA until it finds the Circle it. bases “AUG.” 8. AUG is the “start” sig- Along the rest of the mRNA nal for building a protein. strand, circle the bases in It establishes the reading groups of 3. Each group of 3 frame for building the bases is called a codon. protein.

A cell does this: Do this with your model: 9. Transfer RNA (tRNA) Put the window of the Trans- molecules attach to the lation machine over the first 3-letter mRNA codons AUG on the mRNA strand. by complementary base Look at the Amino Acid Co- pairing. At the other end, don Chart; notice that AUG they carry an amino acid. codes for methionine (M). M is already marked in the first square on your protein strip. 10. The ribosome slides Slide the window of the along the mRNA, moving Translation machine to the 3 bases at a time. Inside next group of 3 bases (codon). the ribosome, each codon Look up the codon on the recruits a tRNA molecule, Amino Acid Codon Chart, and which brings in the next write the one-letter code in amino acid. The ribosome the next square on the protein links the amino acids strip. together to start building a protein. TIP: To use the chart, find the first letter of the codon in the center and read outward to find the right amino acid. 11. The ribosome con- Continue sliding the Transla- tinues along the mRNA tion machine along the mRNA molecule, reading codons strip, looking up each codon and adding amino acids to on the table, and writing the the growing protein chain. amino acids’ one-letter code on the protein strip. 12. When the ribosome When you reach a codon that reaches a STOP codon, codes for STOP in the Table, the mRNA and the fin- your protein is finished. ished protein are released. 13. Real proteins are You have just transcribed and often hundreds of amino translated a very small piece acids long. of a real gene!

The cell can read same Compare your amino acid mRNA strand again to sequence to the 5 Protein build another protein. pages to learn more about the protein youjust built, and what organism it came from.

U C G = S F G L E S A G U C D U C A G AG UC C A Y A U G G G U U P A C TO C A C A S U G G C A U C V A C P C A STO U U G U G G W G U R A G U C C A C A L S U G G U A A C C K C A U C A G G U P A U G C N C A U G G A C A C U H T U G Q

/START I R

Amino acid side chains

A C D E F G H I K L

Alanine Cysteine Aspartic Glutamic Phenylalanine Glycine Histidine Isoleucine Lysine Leucine (Ala) (Cys) acid (Asp) acid (Glu) (Phe) (Gly) (His) (Ile) (Lys) (Leu)

M N P Q R S T V W Y

Methionine Asparagine Proline Glutamine Arginine Serine Threonine Valine Tryptophan Tyrosine (Met) (Asn) (Pro) (Gln) (Arg) (Ser) (Thr) (Val) (Trp) (Tyr)

Second Letter UCAGU C G = S F UUU UCUG UAUL UGU U F E Y C UUC UCC UAC UGCS C D C SA G U C A U GSTOP STOP A U UUA UCAAG UAA UC UGA L C A Y UUGA U UCG UAG STOP GUGG W G G G U U P CUU A CCU CAU CGUC TO U C A CH A S CUCU CCC CAC CGCG C G L C P A U R C Third Letter C VCUAA CCA CAA CGAC A Q STOP CUGC CCG CAG CGGA G U U G U G G W AUUG ACU AAU AGUU U R A N C S AUC I ACC AAC AGC C First Letter G U C AT C A L A SAUAU ACA AAA AGAG A G K U R M A C AUG ASTART ACG AAG AGGC G K C A GUU U GCUC GAUA GGUG P U G D U GUCN AGCC U GACG CGGC C C A G G V U G A U G GUA GCAA C U GAAG A C GGAH A T E GUG GCG GAG QGGG G