1. The Central Dogma Transcription & Translation

2. Transcription and Translation
8/24/2018
The “Central Dogma” of Molecular Genetics
Transcription
Translation
DNA
RNA
Protein
Trait
RNA processing
G. Podgorski, Biol 1010

3. Transcription and Translation: An Overview (aka the Central Dogma)

4. Transcription DNA RNA What is the difference between DNA and RNA?
Ribose Sugar
Uracil not thymine

5. RNA vs. DNA DNA Double stranded Deoxyribose sugar Bases: C,G A,T RNA
Single stranded
Ribose sugar
Bases: C,G,A,U
Both contain a sugar, phosphate, and base.

6. Transcription and Translation
8/24/2018
RNA Is Largely Single-Stranded
G. Podgorski, Biol 1010

7. Transcription and Translation
8/24/2018
There are Different RNAs with Distinct Functions
Recently, a new class of RNA, microRNA, has been shown to regulate gene expression.
G. Podgorski, Biol 1010

8. Transcription Where? What? When? Why? How? Nucleus in Eukaryotes
Cytosol in Prokaryotes
What?
RNA Polymerase plus some minor proteins
When?
When RNA is needed
Why?
RNA’s serve many important functions in cells
How?

9. Transcription The transcriber is RNA polymerase.
It binds to one DNA strand at a site called the promoter
It then moves along the DNA pairing complementary Nucleotides.
It disengages at a stop signal

10. Transcription and Translation
8/24/2018
Transcription is a Key Step in Gene Expression
Transcription makes an RNA copy of DNA.
G. Podgorski, Biol 1010

11. TRANSCRIPTION DNA - RNA
ACGATACCCTGACGAGCGTTAGCTATCG
UGC
UAU
GGG
ACU

12. Transcription and Translation
8/24/2018
RNA polymerase acts here
The enzyme RNA polymerase opens the DNA strands and synthesizes an RNA complementary to only one of the DNA strands.
G. Podgorski, Biol 1010

13. Transcription and Translation
8/24/2018
Transcription
A gene
The decision to transcribe a gene is the most important step in the control of gene expression.
Transcription starts and stops at distinct sites at the ends of a gene.
Animation
G. Podgorski, Biol 1010

14. Transcription is done…what now?
Now we have mature mRNA transcribed from the cell’s DNA. It is leaving the nucleus through a nuclear pore. Once in the cytoplasm, it finds a ribosome so that translation can begin.
We know how mRNA is made, but how do we “read” the code?

15. Translation
Second stage of protein production
mRNA is on a ribosome

16. Reading the DNA code Every 3 DNA bases pairs with 3 mRNA bases
Every group of 3 mRNA bases encodes a single amino acid
Codon- coding triplet of mRNA bases

17. Transcription and Translation
8/24/2018
The Genetic Code is Biology’s Rosetta Stone
These are the words of the genetic language.
G. Podgorski, Biol 1010

18. Transcription and Translation
8/24/2018
The Genetic Language Uses 4 Letters Written Into 3-Letter Words
G. Podgorski, Biol 1010

19. tRNA Transfer RNA Bound to one amino acid on one end
Anticodon on the other end complements mRNA codon

20. Transcription and Translation
8/24/2018
tRNA Is An Adpator That Couples Codons and Amino Acids
G. Podgorski, Biol 1010

21. Transcription and Translation
8/24/2018
Eukaryotic Genes are Segmented
Genes are made of parts represented in the mRNA (exons) and parts that are transcribed but not present in the mRNA (introns).
Introns are removed from the primary transcript and exons are spliced together to make mRNA.
In some genes more than 90% of the pre-mRNA is destroyed, never to appear in the mRNA.
Animation
G. Podgorski, Biol 1010

22. Transcription and Translation
8/24/2018
What Translation Accomplishes
The sequence of amino acids determines the structure, and therefore the function, of a protein.
In translation, information present in the mRNA is read by the ribosome to synthesize a polypeptide.
G. Podgorski, Biol 1010

23. DNA RNA Protein
Cytoplasm
Nucleus

24. Nucleus
Cytoplasm

25. Genetic information usually flows in one specific direction
Genetic information usually flows in one specific direction. Which of the following best represents this flow?
A. DNA to Protein to RNA
B. Protein to RNA to DNA
C. RNA to Protein to DNA
D. DNA to RNA to Protein