Transcript Ch 16-17 High

Ch. 16
DNA
DNA: the Central Dogma,
history, structure
Replication
History: timeline, people and
their accomplishments
•
•
•
•
Mendel (heredity)
Thomas Hunt Morgan (flies, linkage)
Griffith (1928) transformation and mice
Avery and colleagues (1944):
– proposed DNA as the transforming agent
• Chargaff (late 40’s-early 50’s)
– base pairing (AT CG)
• Hershey-Chase (1952) DNA IS hereditary material
• Watson and Crick (1953) (Franklin)
chemical structure of DNA
• Meselson-Stahl mid 1950’s
– DNA Replication details
Griffith:
Transformation
Hershey / Chase
(the hereditary material is not a protein)
Radioactive
P and S
Whose rule?
Purine? Pyrimidine?
You have 6 billion pair
in every cell!
A-T C-G
How’s it all fit?
• DNA coiling – Let’s see it!
Chargaff’s Rule
• Purines (A, G, double rings) always pair
with Pyrimidines (T, C, single rings)
• A-T, C-G (& in RNA? ____)
• Old AP test question: if in a cell the
DNA bases are 17% A’s then what are
the %’s of the other bases?
• CUT your PY or Pure Silver (Ag)
DNA Replication:
SEMICONSERVATIVE
MODEL
How did they (Meselson-Stahl) prove
this? FIG 16.10
KNOW: Steps of Replication
Enzymes
Leading and Lagging strands
Okazaki Fragments
Anti-parallel
Video
“Bubbles”
Replication forks,
simultaneous
replication
Semi-conservative
**Eukaryotes - multiple
origins of replication
**Prokaryotes have one
This process
is fueled
by…
nucleoside
triphosphates
DNA is made from
5’ to 3’ and it is
read from 3’-5’.
The 3’ end is the
end which
elongates (grows)
Why is this
direction important
to consider in
Replication?
What do the terms 5’ and 3’ mean?
Leading &
Lagging
strands,
made 5’-3’
Okazaki
fragments
ENZYMES: helicase,
DNA Polymerase, ligase
(are of the
lagging
strand)
Enzymes :
•Helicase
•Single strand
binding proteins
•Primase
(RNA Primer)
•DNA Polymerase
•Ligase
•Nuclease and
DNA Polymerase
(both are repair enzymes)
Let’s see this in Action
• Leading Strand
(Nobelprize.org)
• Lagging Strand
(Nobelprize.org)
• Overall
(wiley)
• Overall 3D view
(wehi.edu.au or dnai.org)
(Youtube has a music version)
Telomeres
(Ch.16)
Unfilled gap left
at the ends of
the DNA strands
due to the use of
RNA primers
Eventual
shortening of
DNA over time
Dolly, cancer,
HeLa cells
(telomerase
fig16.19)
Enzyme: Telomerase
extends the (3’) long strand
so the 5’ strand can finish.
WOW! ? ? ?
Where is telomerase
naturally found?
DNA from a single skin cell, if
straightened out, would be about six feet
long but invisible. Half a gram of DNA,
uncoiled, would stretch to the sun.
Again, you couldn't see it.
http://www.pixar.com/featurefilms/nemo/images/index_lwide.jpg
Story Time!! (Due Tuesday Nov. 6)
Select a figure, process, topic, or high level vocabulary word from
chapter 16 or 17.
Your job is to make a poster of your selected topic.
-The poster should be kid-friendly as to say an intelligent 8-10
year old would be able to understand it yet make sure that all
information communicated is true to the text.
- Finally, you may not use English, do the best you can, ask
friends, relatives, teachers, etc for help if necessary.
Potential topics include but are not limited to the following…..
Experiments that identified DNA as the “genetic material”, DNA
Structure, DNA Replication, Telomers and telomerase,
Transcription, Modification of RNA, Translation, Mutations.
Ch.17 One gene/One
polypeptide
Define transcription and
translation
Compare Prokaryotic and
Eukaryotic cells
video
• (21 different
AA’s)
• mRNA code
• Ave. protein
is 400AA
long
• Titin is
30,000AA
long!
(this is _____
nucleotides?)
• DNA=
triplets
• RNA=
codons
• 5’ to 3’
• Pre-
mRNA
(primar
y
transcri
pt)
• Promoter:
TATA Box
• Transcription
factors
• RNA polymerase
• Transcription
initiation
complex
• Movie
Finishing the premRNA
Introns: (intruding) spliced out
Exons: kept, will be Expressed in
the cell
• snRNP’s
identify
introns
• Introns are
cut out at a
Spliceosome
• Final mRNA
has only
genes that will
be transcribed in cell
no “junk
genes”
• video
• Translation
• The production
of
polypeptides
• On a Ribosome
• tRNA, transfer
RNA carries in
the amino
acids to the
ribosome
(transfers
the
A.A)
Read 5’ to 3’
• A P E:
• AminoacyltRNA
synthetase
• Peptidyl tRNA
binding site
• Exit
• Video
• Movie
Termination of the
translation
Translation of many
polypeptide chains at once
The signal mechanism: signal peptides
Free or bound ribosomes?
• Coupled
transcrip
tion and
translati
on
One base difference out
of 574 Amino acids
(1722 bases)
The wrong protein
Nothing formed
•Happy
Homecoming
(again!)
•Have fun, be safe
Repairing
mistakes