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Living Environment – Lesson 61
Danta/Meeker
Name_________________________
The Genetic Code
Do Now: Why must DNA be converted into RNA before proteins can be made? (Lesson 58/59)
Explore: Read the article and answer the following questions
One of the greatest facts of the central dogma is that the genetic code is the same for almost every
organism on earth in every cell. This means that the same DNA sequence would lead to the same proteins
being made in two different organisms. One exception to this is the human mitochondria, which uses its
own genetic code. The fact that mitochondria use a genetic code slightly different than most other cell
types shows that mitochondria may have arisen (come up) by a unique process. Luckily, the mitochondria
having their own code is not harmful to organisms usually. One example of a difference is that
mitochondria has one less stop codon, which tells the ribosome to stop making the protein. This could be
dangerous if a mutation leads to the creation of these stop codons, yet proteins keep being made.
However, this is extremely rare, and every cell has ways to prevent this from being an issue.
What is true of the genetic code for nearly every organism?
What organelle is the exception to the rule? ___________________________
How are mitochondria different?
What caused this difference? (How did it happen?)
*Challenge* How could scientists use this mitochondrial code to study how related organisms are?
Codon
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Series of ____________________________
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Codes for one _________________________
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Made of ___________, ___________, ___________, ___________
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__________ different codons
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Living Environment – Lesson 61
Danta/Meeker
Genetic Code
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Is the same in almost _______________________
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Carried from ______________________________
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Determines the creation of _______________________
Degeneracy: Multiple ____________ code for one _____________________
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Can have a mutation with _____________________________
o __________________ mutations
Universality: Most organisms use the same _______________________
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Exception: ______________________________
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Can understand what proteins are being made from _______________
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Shows probably __________________________
Why do you think there is a universality to the genetic code?
Unambiguity
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One _______________ codes for only ___________________
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No mistakes in _________________________
UAG=
AUG=
CGA=
GCG=
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Living Environment – Lesson 61
Danta/Meeker
CAU=
CAC=
What is true of CAU and CAC?
What are the stop codons? ___________________________________________________
What does a stop codon mean?
Practice
1. Make a protein!
Step One: The DNA strand below is inherited.
TAC CTA TCA ACA ACT
Step Two: Transcribe the DNA into RNA.
____ ____ ____ _____ ____
Step Three: Translate the mRNA into an amino acid sequence.
_____ _____ _____ ______ _____
2. Identify the organelle in which step 2 occurs.
__________________________________________________
3. Identify the organelle in which step 3 occurs.
__________________________________________________
4. State the role of the nucleus in protein synthesis.
5. State the role of the ribosome in protein synthesis.
Draw the Central Dogma (Try doing it from memory)
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