Transcript Protein Synthesis Notes

RNA & PROTEIN
SYNTHESIS
Chapter 12
Section 3
Pages 300-306
I.
RNA
A. What Is It?
1. RIBO-NUCLEIC ACID
- The “Middle-Man” between DNA
(nucleus) & the ribosomes
(cytoplasm).
2. Structure
a. Ribose (Sugar)
b. Single-stranded, not double.
c. Thymine is replaced by URACIL.
- Adenine binds with Uracil.
II.
What Codes For A Protein?
A. The genetic code allows for almost
an infinite amount of different
proteins.
B. Every 3 bases of DNA (or mRNA) is
referred to as a CODON.
- Each codon codes for 1 amino acid.
Example:
GCA codes for the amino
acid Alanine.
C. Proteins are made outside the nucleus.
Why?
That is where they are needed the most!
III. Types of RNA
1. mRNA (Messenger RNA)
a. A copy of the information
found in DNA.
b. Carries instructions to the
ribosomes on how to make a
specific protein.
2.
rRNA (Ribosomal RNA)
- make up ribosomes, which
direct the synthesis of a protein.
3. tRNA (Transfer RNA)
- carries amino acids to the
ribosomes where they are
connected to form proteins.
IV. STEPS IN PROTEIN SYNTHESIS
STEP 1: Transcription
A. The process whereby mRNA is made
from DNA.
- Very similar to DNA Replication.
- Occurs inside the Nucleolus.
1. An enzyme (RNA Polymerase) binds to
an area of DNA called a Promoter.
- Where Transcription will start.
2. RNA Polymerase unwinds & separates
the DNA strand.
- One half will be used as a template to
make mRNA.
3. Complimentary “RNA” nucleotides
match up with each DNA base.
4. A single strand of mRNA continues to
grow until a “STOP” codon is reached.
Transcription Animation
• http://www.biostudio.com/d_%20Transcript
ion.htm
STEP 2: Translation
A. The process of converting the info.
in mRNA into a protein.
- Occurs within the cytoplasm.
1.
mRNA leaves the nucleus and binds to a
ribosome.
2.
The ribosome moves along the mRNA
and reads every three bases (codon).
3.
tRNA (compliment of mRNA) picks up
specific amino acids from the cytoplasm
and attaches to the mRNA strand.
4.
The “anticodon” of tRNA temporarily
attaches to its complimentary codon on
mRNA and adds its amino acid.
•
5.
Amino acids are bonded with peptide bonds
forming a polypeptide
This process continues until a “STOP”
codon is reached.
* When complete, a single protein has
been produced.
Translation Animation
• http://highered.mcgrawhill.com/olc/dl/120077/micro06.swf