1. Transcription & Translation
How do we make sense of the DNA message?
Genotype to Phenotype

2. Central Dogma of Cell Biology
DNA codes for DNA = REPLICATION
DNA codes for RNA = TRANSCRIPTION
RNA codes for protein = TRANSLATION

3. Replication vs. Transcription
DNA-DNA
Starts at replication origins
Unwinds with Helicase
DNA polymerase
Proofreads
Start with 1 DNA
End with 2 DNA:
½ new, ½ old
DNA-RNA
Starts at promoter regions
Does not need Helicase to unwind
RNA polymerase
No proofreading
Start with 1 DNA
End with same DNA and 1 RNA

4. mRNA
RNA: Ribonucleic Acid
rRNA

5. Differences between RNA and DNA
Deoxyribonucleic Acid
Double stranded
Deoxyribose sugar
Thymine (A,C,T,G)
DNA polymerase
“Master Copy”
1 major form*
RNA
Ribonucleic Acid
Single stranded
Ribose sugar
Uracil (A,C,U,G)
RNA polymerase
“Working Copy”
3 major forms*
* Can choose to discuss mtDNA here

7. Messenger RNA: mRNA Single-stranded, linear RNA
Carries information from DNA to ribosomes

8. Ribosomal RNA: rRNA
Helps form the structure of ribosomes, along with proteins
Long coils of RNA

9. Transfer RNA: tRNA Short coils of RNA found in cytoplasm
Matches amino acids to mRNA

10. Can you identify the 3 RNAs?

11. Transcription DNA  RNA Occurs in Nucleus
RNA synthesis has three stages:
Initiation
RNA polymerase binds to promoter and unwinds helix
Requires “initiation factors”
Elongation
RNA polymerase builds RNA complementary to the DNA strand
What nucleotides are used?
Termination
RNA polymerase reaches terminator region & releases transcript

14. How do we know what to transcribe?
Promoter
Characteristic region of DNA that signals the start of a gene.
A sequence of letters that signals “gene ahead!”
“TATA box” and enhancers

15. Promoters

16. How do we know what to transcribe?
Start and stop codons
What are codons?
Each 3 bases form a codon that codes for a particular amino acid
AUG  methionine amino acid, but also START
UAA, UGA, UAG  STOP

17. How do we know what to translate?
Not all of the message is turned into protein
Before the mRNA message leaves the nucleus, RNA editing & modifications occur
DNA & RNA contain sequences that do not code for proteins = INTRONS
INTRONS = IN (BETWEEN) RONS
Sequences that code for proteins are expressed = EXONS
EXONS = EX (PRESSED SEQUENCE) ONS

19. 9.4 RNA Processing Primary transcripts contain extra nucleotides
Introns vs. exons
Splicing
Add cap and tail for protection from nucleotide degrading enzymes
tRNA processing also involves forming shape by base pairing or rRNA forming into ribosomes

20. Splicing

21. Why do introns exist? The presence of introns
Allows for alternative RNA splicing
Proteins often have a modular architecture
Consisting of discrete structural and functional regions called domains
In many cases
Different exons code for the different domains in a protein
Gene
DNA
Exon 1
Intron
Exon 2
Exon 3
Transcription
RNA processing
Translation
Domain 3
Domain 1
Domain 2
Polypeptide

22. mG cap and pol- A tail Added before mRNA leaves nucleus
Cap directs mRNA to ribosome
Protects ends from nucleases

23. If you were given this DNA sequence, what would be the mRNA
If you were given this DNA sequence, what would be the mRNA? TCGATGTTCCGCCGTACGTCGTAACCG
AGCTACAAGGCGGCATGCAGCATTGGC
Use the bottom strand as the coding strand
Where would the message begin?