Transcript tRNA

Success
Announce in DNA week (previous lab) that 50 points of quiz will
be moderately detailed, understanding-requiring Manual reading
Supplementing with textbook not a bad plan on their part
Updates:
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Last quiz average: 77%, Review “Hypothesis”
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Pattern master write ups have been graded (RUBRIC!)
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Mix and match liquids labs are graded. Late submissions and
submissions that weren’t turned into the dropbox received half
credit.
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When is HW due? It will NOT be accepted late any more.
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Remember the Spider
Dance?
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Why do they do that?
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How do they know to do that?
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QUIZ TIME
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Did we all read the chapter? Did we all read the vocabulary in the
back?
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Let’s do a quick review of TRANSCRIPTION AND
TRANSLATION
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How?
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Why?
Transcription:
Writing again
Translation:
Changing
languages
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Today
we’ll go
from
here...
We can do
anything
Text
To here
Off to see the wizard...
Sending ‘messages’ out from DNA
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DNA replication
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both strands => new DNA
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=> new cell
Transcription
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1 strand => new RNA
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=> new protein
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Transcription: seeing it
http://www.hhmi.org/biointeractive/media/DNAi_transcription_vo1-lg.mov
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Amino acids
From 4 letters of storage/information
to
20 letters of action!!
20 toys
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EVERY one has a blue part. Chem name?
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EVERY one has a red part. Chem name?
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Thus these are all...?
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How many are there (possible)?
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Different
tools;
different
jobs
• You & partner have an amino acid; which is it? (StructViewer or
homepage => left column ‘big twenty’ amino acids)
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In what ways are all bases identical? Different?
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In what ways are all amino acids identical? Different?
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Which set is more diverse in terms of ‘feel’?
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Which more diverse in terms of shape?
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Which would allow you to build more diverse shapes &
surfaces?
Amino Acids
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How are they similar?
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How are they different?
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What do the differences mean in terms of feel?
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How are they similar to nucleic acids?
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How are they different?
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Mutation--not always
bad
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While the comparison is often made, proteins are not
sentences
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An amino acid is a collection of properties; changing from
one to another changes a region of the protein by
(little/some/a lot/completely)
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It’s an exaggeration, but think of amino acids more like
different vacuum cleaner nozzles
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How does a codon ‘mean’
an amino acid?
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A little Vocab
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DNA
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mRNA
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rRNA
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tRNA
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Codon
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Anticodon
Blinding you with Science (jargon)
RNA Polymerase: joins RNA links into a chain
mRNA: messenger RNA; RNA string copied (‘transcribed’) from DNA
tRNA: transfer RNA; one of many RNA molecules that carry specific amino acids
ribosome: giant machine (>200 proteins, 4 RNAs (2 > 1000 nucleotides) that
oversees the reading of the mRNA and the creation of polypeptide
aminoacyl tRNA synthetase: protein machine adds amino acid to tRNAs
Termination factor: ‘reads’ UAA etc., => ribosome looses the peptide & falls
apart
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Walking the walk
How bio machines translate the language of
nucleotides into an amino acid string
Types of bonds
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VELCRO: a bond that can be cheerfully broken/re-made during
lab
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Duct tape: same at the molecular level, but at the 181L student
level, breaking such a bond gets you a zero on this week’s quiz
Roles--for single
mRNA
5’ end is pointy/spiky
3’ end is soft/furry
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4 pairs to be tRNA
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4 pairs to be Aminoacyl tRNA Synthetases
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1 large ribosomal subunit (1 person)
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1 small ribosomal subunit (1 person)
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2 to be (RNA polymerase & the mRNA it makes )
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1 termination factor (2 people)
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Learning your ‘lines’
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Handout: Each group find questions related to their role;
answer them
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Lab manual, textbook, internet OK as sources
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Meet your blocks-- 5’ is the end that sticks to hair, socks,
shirts
5’ end is pointy/spiky
3’ end is soft/furry
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DNA template strand
5’ CTTAAATCCGAATGCCCATG 3’
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DNA template strand
(alternate version)
5’ CTTAAATCCGAATGCCCATG 3’
5’ end is pointy/spiky
3’ end is soft/furry
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Special powers
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Recall that ribosome assembly is the result of methionine
tRNA finding a match on mRNA in presence of small
ribosome subunit
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Only methionine tRNA (it will ‘know itself’ once crowned by
the synthetase that hands out met) can team with small
ribosomal subunit & join with the ‘AUG’!
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Going with the flow
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mRNA at the central bench
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ribosome assembles around it
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synthetases at bench corners (or ‘diffuse’ opp. direction vs. tRNA)
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tRNAs will ‘diffuse’ by following a path through the room (clockwise
or counterclockwise)
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When any event first happens*, action stops, molecules involved
will announce, explain
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Go until a protein happens
*This includes non-events (rejections, etc.)
Walk-through with 1 tRNA
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Everybody watches visits to synthetase, ribosome
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In the real world, everything is happening all the time;
all is happenstance
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Now we’re dividing into 2 smaller groups and
you will do the activity
Roles--for TWO
mRNA
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4 tRNA
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4 synthetases
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1 ribosome
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1-2 to be (RNA polymerase & the RNA it makes )
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1 termination factor
5’ end is pointy/spiky
3’ end is soft/furry
DNA template strand
(alternate version)
5’ CTTAAATCCGAATGCCCATG 3’
5’ end is pointy/spiky
3’ end is soft/furry
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Who knows the code?
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What happens if a tRNA carries the wrong amino
acid?
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What happens if the mRNA contains a copy error
relative to DNA?
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What happens if a tRNA has a mutated anticodon
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Review movie
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(in TA desktop folder)
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Exit Condition
1.) Pair up (two in a group)
2.) Write your names and SECTION (25) at the top
of the paper
3.) EXPLAIN the process of TRANSLATION
Include the following in your answer:
tRNA
mRNA
ribosome
AUG codon
RNA Polymerase
aminoacyl tRNA synthetase
termination factor
diffusion
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Meet your
semester-long
interest
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Homework