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Protein Synthesis
From Codes/genes to Proteins/machines
Central Dogma- DNARNAProtein
It explains how genetic information flows
Can you break the code???
8 5 12 12 15
3 12 1 19 19
Making Proteins
Protein Synthesis
Process of making
proteins
Two part process
1. Transcription
2. Translation
Remember Reading DNA?
The four chemical bases in
DNA (A, T, C, G) create a
code/gene
Ribosomes “read” this DNA
code/gene to make proteins.
Where are ribosomes
located?
Where is DNA located?
Nucleus Problem
Nucleus not permeable to DNA
DNA is a large to fit out of pore
Double stranded = wide
How do we get the code/gene
to the ribosomes to make
proteins?
Copy code into a smaller
molecule
RNA (ribonucleic acid)
RNA vs DNA
• What is the difference?
• Compare and contrast
DNA to RNA
DNA
BOTH
RNA
Two Types of Nucleic Acids
Deoxyribonucleic Acid
Ribonucleic Acid
DNA
RNA
Double Stranded
Single Stranded
Smaller
Nucleotide sugar =
Nucleotide sugar =
Deoxyribose
Ribose
Bases = A, T, G, C
Bases = A, U, G, C
The Tail of Two RNA’s
Two RNA types needed for Protein synthesis
mRNA
messenger RNA
tRNA
Transfer RNA
rRNA
Ribosomal RNA
Protein synthesis
Step 1: Transcription
Process of making messenger RNA (mRNA) from
DNA
Exactly like Replication (with one small difference)
Use base paring rules
C pair with G
G pair with C
T pairs with A
BUT
A pairs with U (uracil)
Which enzyme is used to add nucleotides??
Modifications of Mrna before it can leave nucleus
Add5’ cap- protects mRNA and allows it to leave nucleus/find a
ribosome
Poly (A) tailThey are added to: protect mRNA and allow it to leave nucleus/find a
ribosome
Introns (non-coding sequences between exons) are removed and exons
(amino acid coding sequences) are spliced together
mRNA Function
Take gene from nucleus to ribosome
Disposable copies(often thousands) of
VERY important information
Tells Ribosome how to build protein.
Transcription Practice
(DNA to mRNA)
Cheat Sheet
A=U
T =A
C=G
G =C
Open DNA:
A T G C C G T T A A C G A G T C T
mRNA copy:
U
Step 2: Translation
What does it mean to Translate something?
Change from one language to another
Biology Translation
To go from the language of DNA (A, T, C,
G, and U) to the language of protein
(amino acids)
Amino acids are the building blocks of
proteins
Translation
Involves ribosome, mRNA and tRNA (transfer RNA)
Ribosome reads mRNA on codon (3 bases) at a time
tRNA matches with codon on mRNA
Brings amino acid with
Ribosome takes amino acid from tRNA and links it to
growing protein
Translation summary
mRNA read by ribosome in
groups of 3 bases called
CODONS
Ex: AUG = Start making protein
Ex: UGA = Stop making
protein
Codon on mRNA match Codon
on tRNA
Codon tells ribosome what
amino acid to attach to protein
Decoding mRNA
Humans use decoder
Codon wheel
Codon chart
Reading Codon Wheel
Using 3 base Codon
Start at center of the wheel
Find the first nitrogen base in codon
Sets what ¼ of circle you will work in
Move to the next ring of circle
Find second nitrogen base
Sets what ¼ of the remaining circle you are in
Move to the last ring
Find third nitrogen base
Arrive at your amino acid
Finding
Amino acid
for Codon
GAG
Reading Codon Chart
Using 3 base Codon
Start at left side
Find the first nitrogen base in codon
Sets what row you are using
Move to the top of chart
Find second nitrogen base
Sets what column you are using
Find where column and row meet
This is the box you are working in
Find matching Codon in this box
Find the
amino acid
for the codon
CGU
CYU
Transcribe this DNA to mRNA
Translate the mRNA to amino acids
DNA
mRNA
Amino
Acid
T
A
C
G
G
C
A
T
C