1. Transcription and the Genetic Code

2. Today’s Agenda
Notes: Transcription

3. Different Organisms in Nature

4. Bellwork Is the structure of DNA different in different organisms?
Does the code in DNA represent the same thing in all organisms?
What makes these organisms different?

5. Objectives Explain the distinguishing characteristics of DNA and RNA
Describe how mRNA is synthesized
Explain how the code found in DNA encodes for amino acids

6. Key Terminology RNA Messenger RNA Ribosomal RNA Transfer RNA
RNA polymerase
Promoter
Codon
Genetic code

7. RNA Polymer of nucleotides
Like DNA
composed of 5 carbon sugar, phosphate group and a nitrogenous base
Unlike DNA
Ribose sugar (rather than deoxyribose)
Uses the base uracil (rather than thymine)
all other bases the same as DNA
Single stranded (rather than double stranded)

8. Different types of RNA mRNA (messenger RNA) rRNA (ribosomal RNA)
takes information from DNA in the nucleus
to the ribosomes in the cytoplasm
rRNA (ribosomal RNA)
makeup ribosomes along with protein
ribosomes synthesizes protein
tRNA (transfer RNA)
carries amino acids to ribosomes
reads the bases on the mRNA

9. Transcription
Process of producing an RNA molecule based on the sequence of the DNA template

10. RNA Polymerases separates the two strands of the double helix
Enzyme involved in the synthesis of RNA
RNA polymerase binds to the DNA
separates the two strands of the double helix
“unzips” the DNA
Uses one strand of the DNA as the template for the synthesis of RNA

11. mRNA Sequence made is complementary to the DNA sequence DNA contain
mRNA contains
Guanine (G)
Cytosine (C)
Thymine (T)
Adenine (A)
Uracil (U)
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12. PROPERTY OF PIMA COUNTY JTED, 2010
Think-Pair-Share
What is the complementary mRNA sequence for the following DNA sequence? DNA: TAC TTG GGC TCC CTT CTG GGG RNA: _________________________________
3. Think-pair-share
teacher presents a question
teacher gives wait time for student to form answer
teacher instructs students to share their answer with a partner
teacher calls on non-volunteers to share with the class
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13. Cellular Location of Transcription
Eukaryotes
Occurs in nucleus
After mRNA made
it must be processed before transported to cytoplasm
Prokaryotes
Occurs in cytoplasm
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14. Process of Transcription
Involves three steps:
RNA polymerase binding and initiation
Elongation of mRNA
Termination

15. Initiation RNA polymerase binds to promoter Promoter
a specific DNA base sequence that indicates the binding site for RNA polymerase
RNA polymerase binds
initiates the unwinding of DNA

16. Elongation
RNA polymerase begins attaching nucleotides to the newly synthesized RNA

17. Termination RNA polymerase reaches termination site
transcription ceases
Most common termination sequence
AAUAAA

18. Ribosomes Once mRNA is made and in the cytoplasm
the ribosomes attach
they decode the mRNA 3 nucleotides at a time
Each group of three nucleotides = a codon
code for an amino acid that make up the polypeptide chain
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19. Genetic Code Table
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20. PROPERTY OF PIMA COUNTY JTED, 2010
Think-Pair-Share
Identify the amino acid for each of the codons
CAG
AAU
UUG
AUG (start codon)
UAG
3. Think-pair-share
teacher presents a question
teacher gives wait time for student to form answer
teacher instructs students to share their answer with a partner
teacher calls on non-volunteers to share with the class
PROPERTY OF PIMA COUNTY JTED, 2010 3

21. Answer to Practice Problem
CAG = Glutamine
AAU = Asparagine
UUG = Leucine
AUG (start codon) = Methionine
UAG = Stop Codon
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22. Properties of the Genetic Code
Genetic code redundant
most amino acids have more than one codon
Unambiguous
each codon has only one meaning
Code has start and stop signals
Universal
used by all living things

23. PROPERTY OF PIMA COUNTY JTED, 2010
Think-Pair-Share
How does the universal genetic code relate to evolution?
3. Think-pair-share
teacher presents a question
teacher gives wait time for student to form answer
teacher instructs students to share their answer with a partner
teacher calls on non-volunteers to share with the class
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24. PROPERTY OF PIMA COUNTY JTED, 2010
Minute Paper
You have two minutes to write down two key points of today’s lesson.
Be prepared to share.
29. Minute paper or Quick Write
teacher provides a prompt from the lesson
students have one minute to write down a summary of the key points
students compare with a partner
teacher uses a strategy to check all
PROPERTY OF PIMA COUNTY JTED, 2010 24