1. Summarize each of the 6 steps of transcription 2. Make an mRNA copy from the DNA gene:...
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Transcript of 1. Summarize each of the 6 steps of transcription 2. Make an mRNA copy from the DNA gene:...
BELLWORK 1. Summarize each of the 6 steps
of transcription.2. Make an mRNA copy from the
DNA gene:GCATATGCAATGATAGATTGACGTATACGTTACTATCTAACT
3. How did you know whether the gene was on the top or bottom strand?
1. Grade hmw.2. Review the Gel Electrophoresis Lab, complete
conclusion, and hand in. (no make-up, go on class website and look up
directions for alternative assignment)3. Binder organization (to be left behind this weekend for
grading)4. Slate review on RNA types & transcription5. New notes & hand-out on translationNO HOMEWORK. Congrats on finishing science fair
project!!!
No late boards will be accepted AT ALL after today. Go on the class website to get the alternative assginment (not worth as many points, but you still pass if done well)
http://fwsciencejohnson.wikispaces.com
Grade homework: ___/15
#1 = 3 pts for completion #2 = 3 pts for completion #3= 3 pts for completion #4= all 6 drawings done= 6 pts
(at least 3 done= 3 pts)
Make a record of what goes where!!1. Draw a picture of your gel and indicate
where each sample will go (remember there are 8 wells and 6 samples) Measure the distance each dye traveled using the ruler provided.
X
Sample
Load and run YOUR gels!!1. Use the yellow pipettor with a fresh tip to
load each dye sample.2. Raise your hand to have a biotech student
add the buffer when you are done3. Connect cables and run the gel at 125 volts
for 15 minutes. Note the starting time.4. While you wait, make observations and lab
notes. (Note any dye spills or over flow. Did your pipettor tip puncture the gel? Can you see any thing happen in the box?)
5. While you wait, start writing the answers to the questions in complete sentences.
Conclusions—Write these on the back of your DNA lab!1. Which dye is the smallest? Largest? Which dyes
are positive? Negative?2. What dyes make up the unknown (X sample)?3. Compare the relative size of one of the positively
charged dyes, to one of the negatively charged dyes. Identify dyes in this comparison by number and color. Use the side (+ or -) the dye move towards, and measure the distance from the center for this analysis.
4. How about your hypothesis?...Was it correct? Why?Hand into box when finished and get out
notebook and binder, make sure all notes/hmw. Is finished
Binder Check On top: Translation hand-out (from today) Transcription homework (15)* Transcription simulation (10) Transcription In-class practice (10) History of DNA-scientists (10) DNA Worksheet (10)
Get slates out *MUST LEAVE BINDER BEHIND FOR GRADING THIS
WEEKEND Notebook check next week (all even pages filled
in, 3 ?s, summary at the bottom)
Protein Synthesis
To get from a DNA gene to a protein, the cell has to perform protein synthesis.
It requires 3 types of RNA: mRNA rRNA tRNA
It happens in 2 parts: Transcription Translation
Open binder to Transcription homework. Make SURE YOUR NAME IS ON the homework.Put binder on lab bench in order of last names:
Translation
Translation is the process of making an amino acid chain from the instructions coded in the mRNA. Occurs in cytoplasm.
Translation Video Clip
http://www.youtube.com/watch?v=41_Ne5mS2ls (start @ 1:56)
Translation- step 1 Initiation
1. mRNA binds to the ribosome & the ribosome begins reading at the START codon AUG
Mature mRNA
Practice
GCG AUG CUG GGU CGU UAA
Which codon above is the START codon?
On your worksheet, find the START codon in each of the 8 mature mRNA strands
GCG AUG CUG GGU CGU UAA AUG GGU AGC AUC GAU UCU GAU UAA
AUG CGA UUC GAC UGG GAC CCA UAU UAG AUG CGC CGU UUG UGA
GAU CUG AUG CCU AAC UGC AUC UAG GCA AUG CAU AGA UCA GUC CCG UGA
AUG GAC CGA GUU AGC UGA GAU CUG GGC AUG CGA UAC CUC UAA CGA
Translation- step 2tRNA matching
2. The ribosome move along mRNA & reads each codon, matching it up with a tRNA that has the complementary anti-codon
Mature mRNA
Practice
What is the anticodon ontRNA that will match with
the START codon on mRNA?
AUG CCG GCA UGC GGA CUG
On your worksheet, fill out the tRNA anticodons for each codon in the mature mRNA strand
Translation- step 3Elongation
3. Each tRNA that enters the ribosome adds an amino acid to the growing chain. A peptide (protein) bond is formed between each amino acid in the chain.
FYI
There are 20 amino acids Each tRNA can only carry ONE type
of amino acid
tRNA w/ anticodon “UAC” can ONLY
carry methionine (M)
Translation- step 4Termination
3. When a STOP codon (UAA, UAG, or UGA) on mRNA enters the ribosome, the large & small rRNA subunits fall apart and translation ends
Practice
How many amino acids are coded for in the mature mRNA strand below? (hint: think about start & stop codons)
GAU CUG AUG CCU AAC UGC AUC UAG GCA
On your worksheet circle the START codon, Box the STOP codon, and record how many amino acids will be in the chain after translating each of the 8 mRNA strands.
Start:1
2 3 4 5
STOP (no
amino acid)
AUG CGA AUG GAC UGG GAC CCA UAU UAGWhat if there are 2 “start” codons??
Start at the FIRST one and keep going until you hit a STOP!
Practice Putting It All Together
Which of the following am I showing/describing?
DNA mRNA rRNA tRNAProteinThe central dogma
of biology says that ______ RNA
Protein
Practice Putting It All Together
Which of the following am I showing/describing?
DNA mRNA rRNA tRNAProteinMade
with Uracil (U) instead of
T:___________
Practice Putting It All Together
Which of the following am I showing/describing?
DNA mRNA rRNA tRNAProteinAmino
Acids are the small subunits
of ___________
Practice Putting It All Together
Which of the following am I showing/describing?
DNA mRNA rRNA tRNAProtein
Practice Putting It All Together
Which of the following am I showing/describing?
DNA mRNA rRNA tRNAProtein
Practice Putting It All Together
Which of the following am I showing/describing?
DNA mRNA rRNA tRNAProteinTransports
amino acids to the ribosome:
___________
Practice Putting It All Together
Which of the following am I showing/describing?
DNA mRNA rRNA tRNAProtein
Practice Putting It All Together
Which of the following am I showing/describing?
DNA mRNA rRNA tRNAProtein
Practice Putting It All Together
Which of the following am I showing/describing?
DNA mRNA rRNA tRNAProteinReads mRNA
and assembles amino acids into a chain:
___________
Practice Putting It All Together
Which of the following am I showing/describing?
DNA mRNA rRNA tRNAProteinA copy of the
information in DNA that can be taken
out of the nucleus:___________
Open binder to Transcription homework. Make SURE YOUR NAME IS ON the homework.Put binder on lab bench in order of last names:
Translation Simulation
You and your partner will receive an envelope full of mature mRNA transcripts
Take the mRNA out of the nucleus & into the cytoplasm (lab table) for translation
Pull the mRNA through the ribosome, & match up the correct tRNA
Record the amino acids that would be added to the growing chain
Figure out the secret phrase!
**If you finish early, work on your translation HW probs
Simulation Run-down
Each tRNA can only carry ONE amino acid (UAC always carries Methionine)….but were there some amino acids that were carried by multiple tRNAs?
Why might this overlap be beneficial?
Short-cut
mRNA Codon Wheel
Determine an amino acid
sequence from the mature
mRNA…without having to
match up tRNA anticodons!
AUG =Methionine
(M)
Try it out!
Mature mRNA: AUG GAC CGA GUU AGC UGA GAU CUG
Amino Acids: _ _ _ _ _ _ _ _M D R V T stop
Complete the amino acid
sequence on your worksheet using the codon
wheel
Closure- do it backwards
Write a short message using amino acid abbreviations: CAR
Work backwards to write the mRNA:
Add a start & stop codon
Write the complementary DNA gene & make it double stranded:
UGU CGA AGA
AUG UGU CGA AGA UGATAC ACA GCT TCT ACTATG TGT CGA AGA TGA
Closure- do it backwards
Write a short message using amino acid abbreviations: CAR
Work backwards to write the mRNA:
Add a start & stop codon
Write the complementary DNA gene & make it double stranded:
UGU CGA AGA
AUG UGU CGA AGA UGA
TAC ACA GCT TCT ACT
Write the DNA gene onto an index card to
trade with another class
tomorrow! Don’t forget to put your name!
Dear p.2,
Can you figure out the se
cret messa
ge? It’s
on the top strand…
TAC ACA CGT TCT ACT
ATG TGT GCA AGA TGA
Sincerely,
Carlos Caballero
ATG TGT CGA AGA TGA