Transcription/Translation

From DNA to Proteins

Students will be able to:

1) Describe the process of transcription.

2) Describe the 3 differences between DNA and RNA.

3) Describe the role of DNA, mRNA, tRNA, and rRNA.

4) Diagram the structures of DNA, mRNA, tRNA, and rRNA.

5) If given a strand of DNA, be able to draw a transcribed strand of RNA which corresponds to the strand of DNA.

DNA

RNA

PROTEINS

The central dogma in biology states that information flows from

What is DNA?�You may already know that DNA is the “code” of life, but how do our bodies interpret this information? And what do they do with it? �The simple answer is that DNA is a set of coded instructions which tell cells how to make proteins. Each gene, or section of DNA, contains the instructions a cell needs to assemble a protein. �

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Roles of DNA and RNA

3) Describe the role of DNA, mRNA, tRNA, and rRNA.

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What is RNA?

RNA vs. DNA

2) Describe the 3 differences between DNA and RNA.

DNA has two strands, but RNA has only one.

DNA contains the nucleotide thymine, but RNA replaces it with uracil.

DNA contains the sugar deoxyribose, while RNA contains ribose.

DNA must stay in the nucleus, but RNA can travel out.

Both DNA and RNA contain genetic information.

Types of RNA (Roles of the types of RNA)

There are 3 types of protein which all play an important role in the protein synthesis process:

• mRNA carries the information from the DNA in the nucleus to the ribosome where proteins are made
• tRNA brings the amino acids to the ribosome to create the amino acid chain
• rRNA makes up the structure of the ribosome

4) Diagram the structures of DNA, mRNA, tRNA, and rRNA.

DNA

tRNA

Structure of DNA: A double helix. Made of two nucleotides paired together. Each nucleotide has a phosphate group, sugar (deoxyribose), and a nitrogen base (A,T,C,G).

Structure of mRNA: a single stranded chain of nucleotides. Each nucleotide has a phosphate group, sugar (ribose), and a nitrogen base (A, U, C, G). A set of three nucleotides is called a codon.

Structure of tRNA: a single stranded chain of nucleotides which is shaped like a 3 leaf clover. At the bottom of the structure, there is a set of three nucleotides called an anti-codon. On the top is an amino acid.

Structure of rRNA: a series of single stranded chains of nucleotides which is condensed together to make up a ribosome. There are two parts of a ribosome: A large subunit and a small submit. Each subunit is made up of rRNA.

PROTEINS

The DNA and RNA work together to complete one goal: protein production. So what is it about proteins that makes them so essential?

Proteins are massive molecules which are made up of a chain of amino acids. The shape of a protein is directly related to its function, or job.

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What are proteins?

PROTEINS

It is estimated that our bodies make somewhere between 80-400,000 different proteins.

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All of these proteins are made from just 20 different amino acids, and those amino acids are coded for by just 4 different nucleotides (A, T, G, and C).

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Let’s dive in now to the process of protein synthesis and how the cell builds a protein using the DNA instructions.

PROTEIN SYNTHESIS

Objective 3: Explain the process of transcription.

Students will be able to:

1) Describe the process of transcription.

2) Describe the 3 differences between DNA and RNA.

3) Describe the role of DNA, mRNA, tRNA, and rRNA.

4) Diagram the structures of DNA, mRNA, tRNA, and rRNA.

5) If given a strand of DNA, be able to draw a transcribed strand of RNA which corresponds to the

strand of DNA.

Objective 4: Explain the process of translation and how proteins are synthesized.

Students will be able to:

1) Describe the steps to transcribe an mRNA molecule and use the mRNA molecule to produce

proteins.

2) Differentiate between transcription and translation.

3) Diagram the steps and illustrate what happens in each stage.

REVIEW: The Central Dogma in Biology

DNA

RNA

PROTEINS

DNA contains the code that tells a cell which sequence of amino acids should be used to create a specific protein. Since DNA can’t leave the nucleus, that message must first be copied to mRNA before it can head to the ribosome to be interpreted.

STEP 1: TRANSCRIPTION

DNA

RNA

1) Describe the process of transcription.

Transcription is the first step of this protein synthesis.

This process occurs in the nucleus. At this time, DNA is copied to a more portable form called mRNA. mRNA is created after an enzyme called RNA polymerase “unzips” the DNA. A complementary nucleotide is matched to each base pair on one strand of the DNA. This new strand of mRNA will be identical to the opposite side of the DNA except that where the DNA would have thymine, mRNA has uracil.

Try it! Transcribe the DNA:

Match each base pair with its complementary nucleotide. Remember, where DNA would use T, mRNA uses U.

5) If given a strand of DNA, be able to draw a transcribed strand of RNA which corresponds to the

strand of DNA.

How did you do?

Match each base pair with its complementary nucleotide. Remember, where DNA would use T, mRNA uses U.

Objective 4: Explain the process of translation and how proteins are synthesized

• Students will be able to:
• 1) Describe the steps to transcribe an mRNA molecule and use the mRNA molecule to produce proteins.
• 2) Differentiate between transcription and translation.
• 3) Diagram the steps and illustrate what happens in each stage.

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STEP 2: TRANSLATION

RNA

PROTEINS

Translation is the next step of this protein synthesis.

1) Describe the steps to transcribe an mRNA molecule and use the mRNA molecule to produce proteins.

3) Diagram the steps and illustrate what happens in each stage.

This process occurs in the ribosome. At this time, the message contained in the mRNA is translated. Every 3 letters, known as a codon, indicates a specific amino acid. Each codon matches with the anticodon located on a tRNA molecule. Each tRNA molecule carries the amino acid specified by the mRNA which it then adds to the chain. In the ribosome, the mRNA is “read” and codons are added the the amino acid chain, known as the peptide chain.

Try it! Match codons with amino acids:

Match each codon with the correct amino acid, by using the codon chart.

Put it together!

Can you transcribe and translate the DNA to determine the chain of amino acids? Hint: tRNA is just like mRNA where C and G always match and A and U/T always match. Use the mRNA to determine the amino acid, NOT the tRNA.

PROTEIN SYNTHESIS: Common mishaps

Protein synthesis is easy once you get the hang of it! Some common mistakes that students make are:

• Finding the amino acid using the anticodon (tRNA) rather than the codon (mRNA).
• Accidentally using T when they are writing mRNA and tRNA. Remember, RNA never has thymine!
• Switching up the U to match with T when U actually matches with A.
• Remember Transcription makes mRNA. Translation makes proteins.

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TIP: The tRNA should look exactly like DNA except with a U in place of every T.

2) Differentiate between transcription and translation.