Download Protein Synthesis Powerpoint

Protein Synthesis
10.6-10.16
Objectives
- To explain the central dogma
- To understand the steps of transcription and translation
in order to explain how our genes create proteins
necessary for survival.
Review
-
What is DNA?
Where is it located?
What are proteins?
Where are they located?
Central Dogma
Types of RNA
- mRNA= Messenger RNA: takes the code from the DNA and
brings it to the ribosome. It is made during first step
called transcription.
- rRNA= Ribosomal RNA: combines with proteins to make the
structure of the ribosome.
- tRNA= Transfer RNA: carries an amino acid to the ribosome
to be able to synthesize the protein during translation.
Overview of Protein Synthesis
3 Processes:
- Transcription: we take the code from the DNA and turn it
into messenger RNA to send to the ribosome.
- RNA Processing: we modify the mRNA to get rid of noncoding regions. (only in Eukaryotes!)
- Translation: we use the code from the mRNA to determine
which amino acids will be brought over by the tRNA to
construct our polypeptide chain.
Transcription
- In transcription we “transcribe” a strand of mRNA from a
gene.
-
What is a gene?
How many genes are on a chromosome?
What makes genes different from each other?
How do we know what to transcribe?
Steps of Transcription
1. Initiation
2. Elongation
3. Termination
*similar to replication although less enzymes are required
Lets watch...
http://highered.mheducation.
com/sites/0072507470/student_view0/chapter3/animation__mrna_
synthesis__transcription___quiz_1_.html
1. Initiation
- RNA Polymerase attaches to the template strand of DNA at
the promoter region. (RNA Polymerase does it all!)
-
The promoter is a specific sequence that marks the beginning of a
gene.
2. Elongation
- RNA Polymerase begins adding RNA nucleotides that are
complementary to the template strand in the 3’ direction.
3. Termination
- RNA polymerase continues until it gets to the termination
sequence.
-
Termination sequence is a special sequence that signals the end of
the gene.
Grab your paper plasmid!
Transcribe the insulin gene into MRNA and write it on the
back of the plasmid.
Do Now
-
Use your phones to complete the socrative quiz!
Go to socrative.com and click student login
Enter classroom # 981663 and enter your name.
Answer the questions to the best of your ability without
using your notes.
- This will NOT be graded
Continuing Protein Synthesis
1. Transcription
2. mRNA Processing
3. Translation
mRNA Processing
- Eukaryotic mRNA is “processed” before leaving the
nucleus.
- This does NOT happen in prokaryotes.
mRNA Processing
Additions:
- 5’ cap is added (a single G nucleotide)
- A poly A tail is added to the 3’ end (50-250 adenine
nucleotides)
* These are both added for protection against cellular
enzymes and also facilitate ribosomal binding.
* They are NOT translated as part of the protein.
Coding and Non-coding sequences
- Most genes have both
coding sequences called
exons and non-coding
sequences called introns.
- Before the mRNA leaves
the nucleus the introns
are removed.
- Exons are then “spliced”
together. They can splice
in different ways to
produce different
proteins.
Practice With Transcription and Processing
- Complete the mRNA Processing practice worksheet with a
partner.
- We will go over it once you are done!
What labs have we done in our Biotech unit?
Give your own summary of each lab and be prepared to
discuss...
1.
2.
3.
4.
DNA Extraction
Restriction Digest
Paper Plasmid
DNA Goes to the Races
PCR- Polymerase Chain Reaction
- Complete the PCR activity!
Do Now
-
Use your phones to complete the socrative quiz!
Go to socrative.com and click student login
Enter classroom # 981663 and enter your name.
Answer the questions to the best of your ability without
using your notes.
- This will NOT be graded
*Also, hand in your outlines!
Continuing Protein Synthesis
1. Transcription
2. mRNA Processing
3. Translation
Translation
-
Process occurring at the ribosome (in cytoplasm)
The “RNA-->Protein” portion of the central dogma
Involves ALL THREE types of RNA (NO DNA!!)
mRNA codes for the amino acids of the protein which are
brought over by tRNA and the protein is assembled by the
ribosome.
Proteins
- What do we already know about proteins?
-
What are they made up of?
What types of bonds hold them together?
How do the bonds form?
Steps to Translation
1. Initiation:
- The 5’ end of the mRNA feeds through
the ribosomes until it stops at the
start codon- AUG.
-
A codon is 3 bases on the mRNA that code
for a specific amino acid.
-
- The first tRNA anticodon will
hydrogen bond with AUG in the P site
and deliver the first amino acid,
Methionine.
-
An anticodon is 3 bases on the tRNA
Codons
- A codon will code for a specific amino acid.
- Each amino acid can have from 1-6 codons that will code
for them.
-
Ex: Leucine has 6 different codons whereas methionine only has 1!
Ribosome Structure
- The ribosome has 2
subunits
-
1 large
1 small
- The mRNA feeds through
the subunits to make the
protein.
Ribosomal Grooves
- Also called “sites”
-
(APE)
- A Site:initial binding site for
the tRNA carrying new amino acids
(*First tRNA binds to P, all
others bind to A)
- P Site:contains the growing
polypeptide chain as the amino
acids link and form peptide
bonds.
- E Site: (not shown in all models)
site where the tRNA exits once it
has delivered its amino acid.
Codon Charts
Codon Chart Practice
Identify the amino acids coded for by the following codons:
-
UUU
ACG
CAC
UAA*
Steps to Translation
2. Codon Recognition:
- The next tRNA anticodon will hydrogen bind to the mRNA
codon in the A site.
Steps to Translation
3. Bond Formation: The amino acid in the P site will form a
peptide bond with the amino acid in the A site.
Steps of Translation
4. Translocation:
- The tRNA and mRNA shift and the tRNA separates from the
mRNA and is released from the E site.
Steps of Translation
5. Repeat:
- This process repeats numerous times depending on how long
the mRNA is.
Steps to Translation
6. Termination:
- tRNAs keep delivering amino acids until it reaches a stop
codon on the mRNA.
-
Use your chart to determine the 3 stop codons.
Steps to Translation
http://highered.mheducation.
com/sites/0072507470/student_view0/chapter3/animation__how_t
ranslation_works.html
Practice
- Take out the transcription/processing worksheet from
yesterday and translate all of the sequences using your
codon chart!