Download Ch. 12.3 and 12.4 ppt

October 27, 2009
• Write down objectives and activities!
• Record your test grade (MAJOR) on your
new gradesheet for the 2nd nine weeks!!
• Review power standards for Photosynthesis,
Cellular Respiration and DNA…
Protein Synthesis
*Gene Expression*
After replication…
TRANSCRIPTION and
TRANSLATION
Transcription
and
Translation
DNA  RNA
(Transcription)
RNA  Protein
(Translation)
Where do replication and transcription take place? Why?
RNA – The “Other”
Nucleic Acid
Differs from DNA :
1. RNA is a single strand of nucleotides
DNA is a double strand of nucleotides (helix)
2. Ribose is sugar
Deoxyribose is sugar in DNA
3. No Thymine, Uracil (U) replaces Thymine
Three Forms:
•Messenger RNA (mRNA)
•Ribosomal RNA (rRNA)
•Transfer RNA (tRNA)
Key Players:
mRNA – messenger RNA
Leaves nucleus with instructions!
tRNA – transfer RNA
Ribosome - rRNA
Transcription
**Occurs in the nucleus
1. Different enzyme binds to the start signal
on DNA
2. Unwinds and separates DNA
3. One side of DNA is used as the template
to make the copy of RNA
4. RNA Nucleotides bind with complementary bases
(U pairs with A)
5. Complete when enzyme reaches the stop code
T
T
A
T
G
C
A
T
C
G
What will be the complimentary RNA sequence?
New RNA dangles off the enzyme
DNA closes back to a double helix shape
Working copy of RNA is edited
Introns – Noncoding (intervening) sequences–
edited out
Exons – Code for amino acids – (exit nucleus)
spliced together
Example:
ACAAUGGACAGU
is the RNA code
If the code for the protein is
ACUGGU, what are the introns/exons?
Three Types of RNA Made in Transcription
mRNA – Blueprint for protein synthesis travels
from nucleus to ribosome
tRNA – Translates mRNA
code to amino acids
(monomers of protein!)
rRNA – Makes up
ribosomes
October 29, 2009
•
•
1.
2.
3.
4.
5.
6.
7.
8.
Write down your objectives and activities!
Turn in your “Challenge Questions” if you finished
it…if not, get a ZAP pass NOW!
Warm Up: (Write the questions!!!)
What are the 3 differences between DNA and RNA?
Is this DNA or RNA? – TATTAGCTAG
Is this DNA or RNA? – AUAAUCGAUC
What two processes occur in the nucleus?
What is the end result of replication?
What is the end result of transcription?
What is the end result of translation?
What is the end result of protein synthesis?
The Genetic Code
Instructions for building a protein
come from:
Codon – 3 base code on mRNA –
codes for amino acids or is a stop
signal
Genetic code is nearly universal for all
organisms!!
Codons
20 Different kinds of amino acids
Sequence of three bases gives enough different combinations
to code for all of them = CODONS!
64 possible codons –
61 code for amino acids
3 are stop signals
Each codon codes for one AA,
but there is more than one codon for most AA.
The Genetic Code
November 2, 2009
• Write down objectives and activities.
• Turn in homework.
• Get a ZAP pass if you don’t have it!
Warm Up:
1. What is the end result of replication?
2. What is transcription?
3. What is translation?
4. Where are codons located?
5. Where are anticodons located?
6. What kind of RNA is used in transcription?
7. What kind of RNA is used in translation?
Remember the Key Players…
mRNA
tRNA
ribosome
Translation
*Occurs in cytoplasm on ribosomes!
*Strings Amino Acids together to form protein
that will express a gene!
tRNA
RNA folded with three loops
One loop has three nucleotide
sequence (Anticodon)
which is complementary to
mRNA codon
For example, if codon is CAA
anticodon would be GUU…
“End” of tRNA carries
AA that corresponds with
the mRNA codon
(remember: codon comes
from wheel/chart!)
No anticodon for codons
UAG, UAA, OR UGA
(Stop Codons)
Translation
1. mRNA leaves nucleus & binds to ribosome
2. tRNA with anticodon UAC and AA
Methionine binds to start codon
3. Next tRNA
comes to ribosome
4. Enzyme joins
two AA
Ribosome
mRNA
tRNA
5. 1ST tRNA leaves
Amino Acid
Chain
6. 2ND tRNA slides over
bringing the mRNA and
AA chain along
tRNA
tRNA
anticodon
mRNA codon
7. Next codon in ribosome is ready for
new tRNA anticodon
(Process continues…)
8. Continues until stop codon
Finally, Step 9…. Ribosome complex falls
apart releasing new protein!!!
Concept Map
Section 12-3
RNA
can be
Messenger RNA
also called
Ribosomal RNA
which functions to
mRNA
Carry instructions
also called
which functions to
rRNA
Combine
with proteins
from
to
to make up
DNA
Ribosome
Ribosomes
Transfer RNA
also called
which functions to
tRNA
Bring
amino acids to
ribosome