From DNA to Proteins
12.3
The Central Dogma of Biology
DNA codes for RNA, which guides the synthesis
of proteins.
DNA→ RNA→ Proteins
This occurs in all living organisms!
Compare RNA and DNA
- Read sections “The Role of RNA” and
“Comparing RNA and DNA” on pg 362
- Record as many similarities and differences
as possible in your notes.
Types of RNA
1. Messenger RNA
● RNA copy of DNA strand
● direct the synthesis of proteins
2. Ribosomal RNA
● combines with proteins to form
ribosomes
● found in the cytoplasm
3. Transfer RNA
● transport amino acids to ribosomes for
protein synthesis
DNA -> RNA -> Proteins
Process in action!
http://learn.genetics.utah.
edu/content/molecules/firefly/
1. Transcription
Synthesis of mRNA from DNA
● occurs in the nucleus
DNA→ RNA
Read pg. 364
“Transcription”
-Answer the following questions in your notes.
1. What opens and reads the DNA?
2. What language is used?
3. What is the purpose of the RNA?
Stages of Transcription
Initiation: Promoter start codon (AUG) tells RNA
polymerase where to start
Elongation: RNA polymerase pulls in bases and
matches them correctly
Termination: RNA polymerase hits a stop codon and
stops
Stop Codons
UAA
UAG
UGA
Complementary Pairing
DNA
-A
-C
-G
-T
mRNA
-U
-G
-C
-A
2. RNA Editing
mRNA is edited
● introns are cut out
● exons remain
● 5’ end cap is added
● Poly-A tail is added to 3’ end
Let’s Edit
“The dog dog ran away back forward
from home yesterday now.”
What words are unnecessary?
After editing the mRNA is sent out into the
cytoplasm to start translation.
Read Pg. 368-369
“Steps in Translation”
Answer the following questions.
1. Who is translating the mRNA?
2. What two languages are involved?
3. What is the final product?
3. Translation
mRNA → Protein
● tRNA reads mRNA using an anticodon
○ binds corresponding codon and attaches amino acid
Stages of Translation
Initiation:
1. mRNA enters ribosome
2. tRNA binds start codon (AUG)
3. translation begins
Elongation:
1. tRNA enters ribosome, binds codon, and
attaches amino acid
2. rRNA hooks amino acids together
3. tRNA exits ribosome and next tRNA enters
Termination:
1. Synthesis continues until stop codon
● tRNA can’t bind stop codon
Watch Video
Let’s Practice
- Go to Photon
- learn.genetics.utah.edu
- Molecules of Inheritance
- then click on Transcribe and Translate a Gene