7.3: Transcription and Translation
- Page ID
- 133657
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Transcription and translation put DNA to work. DNA contains many smaller segments called genes -- sections of DNA that code for a protein. These genes cannot directly produce these proteins however, and so the cell must create temporary copies of these segments to use elsewhere in the cell.
To transcribe quite literally means “to put into written or printed form.” This is a very close description as to what is happening in the cell. Since the DNA cannot directly make proteins, mechanisms are in place to read and transcribe DNA’s genes. Instead, mRNA is made by RNA polymerase, which reads the opened DNA strand. When RNA polymerase reads the DNA, it uses the complementary base pair rules to select the correct base for mRNA it’s building. Then, the mRNA molecule is released and leaves the nucleus.
RNA polymerase needs direction on where and when to start the transcription process. Since the cells do not need to use every gene all the time, it’s important that there is a way to regulate when genes are used. The promoter is a special section of DNA that comes before the gene and helps dictate if a gene should be used often, sometimes, or hardly ever.
OpenStax, CC BY 4.0, via Wikimedia Commons
| Role in Transcription | |
|---|---|
| Promoter | Regulates when a gene will go through transcription |
| RNA polymerase | “Reads” DNA and builds the mRNA strand |
| mRNA | Carries the information from the transcribed gene |
| DNA | Encodes information in the form of genes to be read and used |
Translation puts the mRNA produced during transcription to work. The mRNA molecule leaves the nucleus and enters into the cytoplasm. We can describe translation in three steps.
Initiation: Once in the cytoplasm, a ribosome will grab onto the mRNA.
Elongation: The ribosome reads mRNA three bases at a time. These three bases are called a codon and dictate which amino acid is next in the sequence. This codon binds with the anticodon of tRNA in the ribosome, which brings the appropriate amino acid.
Termination: When a STOP codon is reached, it causes the ribosome to let go of the mRNA molecule and protein strand.
Now we will take RNA strands and translate it into a sentence. For this activity, transcribe the DNA strands below and identify the codons in the message. Then, look around the room for cards showcasing each codon (we will avoid using anticodons for simplicity.) The opposite side of the card will have a word that you will write down below. After you find all the anticodons, you should have a complete sentence for your answer.
1. DNA: T T T A G C C T A G C T A A A T T T C A G T G C
mRNA:
Protein:
2. DNA: T T T T G A G G C G C T G T G T T T G T C
mRNA:
Protein:
3. DNA: T T T C A G T T C C A A A A A T T T A G C C T T
mRNA:
Protein:
4. DNA: T T T G G T A A T G G G G T A C A G T T G
mRNA:
Protein:
5. DNA: T T T T T A A A G G G A G C T T G G G A G T T T T G C
mRNA:
Protein:
6. DNA: T A A G A T G T A A G C A A C C C T
mRNA:
Protein:
7. DNA: T A A A G G C C G A A C G T T
mRNA:
Protein:
8. DNA: C A G G A A T G T T A G C C A T C T
mRNA:
Protein:
9. DNA: T A A A G G A C C T C G
mRNA:
Protein:
10. DNA: T T T T G A G G C G C T C G C T T T C A G C G A
mRNA:
Protein:
11. DNA: T A A A G G A C C A A G T C C C G T
mRNA:
Protein:
12. DNA: T A A C G G G T A G G T A A T
mRNA:
Protein:
13. DNA: T T T A G C C T A T A T T T T T G A C T A
mRNA:
Protein:
14. DNA: T T T A A C A A T T A C T C A T T T T G C
mRNA:
Protein:
"Protein Synthesis Activity" by Aimee Mazzoni, Reedley College is licensed under CC BY 4.0