Transcript DNA (Deoxyribonucleic Acid)

How does DNA copy itself?
Purpose: DNA copies itself to
ensure that each new cell that is
produced in gets the correct number
of chromosomes and receives an
EXACT copy of the DNA molecule.
Replication must occur before cell
division.
• This is called DNA
REPLICATION.
• The DNA molecule serves
as its own pattern or
template so as an exact
copy can be made.
Watson and Crick
• The model that Watson and Crick where
the nitrogen bases pair suggested a
mechanism for DNA to replicate.
Messelson and Stahl
• They proved that DNA is semiconservative
by attaching radioactive material to DNA.
As the cell divided, they observed the new
DNA in each cell and saw that it contained
half of the old.
• Semiconservative: contains half of the old
strand when DNA is replicated.
STEPS OF DNA REPLICATION
1. Helicase begin to unzip the double helix
at many different places. The hydrogen
bonds between the bases are broken.
Occurs in two different directions.
2. Free floating in the cytoplasm
nucleotides pair with the bases on the
template. DNA polyermase bonds together
the nucleotides. Small segments are
bonded together.
3. Two identical strands of DNA result.
The DNA will twist back together.
DNA is called
SEMICONSERVATIVE because it
uses an old strand to make a new
one.
This results in 2 new identical DNA
molecules.
DNA Replication Video
http://www.youtube.com/watc
h?v=zdDkiRw1PdU&feature=
player_embedded
DNA Replication Fork
Point where DNA is split apart to
replicate. Forms a Y!
Role of Enzymes
• 1. Helicase
unzips the two
DNA strands.
• 2. DNA
polymerase is the
enzyme that joins
individual
nucleotides to
produce a new
strand of DNA.
Proofreads DNA
when finished!
DNA Replication in Prokaryotic
Cells
• 1. Proteins binds to
starting point.
• 2. Starts at a single
point and proceeds in
both directions.
Eukaryotic Replication
• Since eukaryotic cells
are so much bigger,
the replication will
start at dozens to
hundreds of different
places on the DNA.
Transciption – Making of RNA
• Transcription – process of copying DNA
to produce a complimentary strand of
RNA. Transcription is making RNA from
DNA
• Purpose = to make
RNA that is
complimentary to the
DNA
Types of RNA
There are three (3) types RNA:
1. Messenger RNA – (mRNA) carries
messages from the DNA in the
nucleus to the cytoplasm
(ribosome).
2. Transfer RNA – (tRNA) 20 different
kinds which are only able to bond
with one (1) specific type of amino
acid. Carries the amino acids to
mRNA.
Types of RNA
• 3. Ribosomal RNA – (rRNA) major
component (part) of the ribosomes
RNA TRANSCIPTION
Transcription – the process by which DNA makes
RNA.
Steps in RNA Transcription:
1. A special enzyme tells DNA its time to
make RNA.
2. The enzyme tells the nucleotides to
only bond with RNA nucleotides.
-The code letters for RNA are: A, C, G and
U.
RNA TRANSCIPTION
3. Process occurs just like DNA
replication
--When complete, only a single strand of
RNA is formed UNLIKE DNA’s double
strand.
--All three types of RNA are formed this
way.
--All leave the nucleus and travel out into
the cytoplasm.
Transcription Video
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RNA TRANSLATION
Definition=Protein Synthesis: the formation of a
protein using information coded on DNA and carried
out by RNA in the assembly of amino acids.
Proteins are:
a. Amino acids in chains – 20 kinds
b. Made of 10’s or 100’s or 1000’s of amino acids
c. Must be arranged in a specific sequence for each
type of protein
d. Function & type of protein is determined by amino
acid sequence
e. DNA makes RNA
f. RNA orders the amino acids
RNA TRANSLATION
Translation Process:
1. mRNA goes to the ribosomes, tRNA
goes to the cytoplasm.
2. tRNA picks up amino acids& brings them
to the ribosome.
3. mRNA tells tRNA in which sequence to
assemble the proteins.(mRNA is the template!)
4. An amino acid chain is a protein.
RNA TRANSLATION
So WHAT??:
DNA makes
RNA
RNA makes
amino acid
chains
Amino acid
chains make
proteins
Proteins make cells
Go to gslc.genetics.utah.edu/units
Translate & Transcribe a Protein and
What is a Protein?
Translation
• Groups of 3 nucleotides on the mRNA
code for each amino acid to build a
protein.
• These groups of 3 are called: CODONS
• The tRNA brings the correct amino acid to
the chain.
• You will build your own proteins tomorrow
with the mRNA that you made yesterday!
We have been told that DNA is the blueprint for life,
BUT what does that mean?
DNA holds the instructions that
tell a cell how to construct
amino acid chains.
That is
important
because
amino acid
chains build
proteins.
AND
Proteins
build
cells
Steps to Protein Synthesis
• 1. DNA replication – make new DNA
• 2. Transcription – DNA message given to
RNA
• 3. Translation – RNA is translated in
amino acid chains(protein).
Prokaryotic - Protein synthesis
• Location – cytoplasm
• At the same time.
• Eukaryotic – Protein synthesis
SO, HOW DOES AN AMINO
ACID CHAIN GET BUILT?
Well, first we have to make somethin
RNA stands for ribonucleic acid
It differs from DNA in three ways:
1. RNA is single stranded.
2. The sugar in RNA is called ribose.
3.Uracil is one of the bases in
RNA. There is NO thymine in
RNA. This means A goes with
DNA Replication
• Replication: coping of DNA
• The DNA molecule produces 2
IDENTICAL new complementary
strands following the rules of
base pairing:
A-T, G-C
•Each strand of the
original DNA serves as
a template for the new
strand
Semiconservative Model
• Replication is called semiconservation
because one strand of DNA is used to as a
template to make the new DNA.
Steps of DNA
Replication
1.DNA unzips and the
hydrogen bonds between
the nitrogen bases pulled
apart. The base pairs are
separated and are left
exposed. This occurs in
two different directions.
This occurs along
hundreds of different
places at a time.
.
DNA Template
Parental DNA
New DNA
Steps of Replication
2. Free-floating
nucleotides are
paired up to the
free nucleotides.
DNA polymerase
bond the
nucleotides
together.
3.Two identical
strands result.
DNA polymerase
checks for
mistakes when
complete.
DNA Replication
• DNA has 80 million base pairs in a
chromosomes. DNA is copied at about 50
base pairs per second. This would take a
month if replication did not occur at hundreds
of different places at once.
Replication Quiz
A---?
G---?
2. Describe how replication works. C---?
T---?
A---?
3. Use the complementary rule to
G---?
create the complementary
A---?
strand:
G---?
C---?
A---?
G---?
T---?
1. Why is replication necessary?
Replication Quiz
A---T
1. Why is replication necessary?
G---C
So both new cells will have the correct
C---G
DNA
T---A
2. When does replication occur?
A---T
During interphase (S phase).
G---C
3. Describe how replication works.
A---T
Enzymes unzip DNA and complementary
G---C
nucleotides join each original strand.
C---G
4. Use the complementary rule to
A---T
create the complementary strand:
G---C
T---A
(1961)
Watson & Crick proposed…
• …DNA controlled cell function by
serving as a template for PROTEIN
structure.
• 3 Nucleotides = a triplet or CODON
(which code for a specific AMINO ACID)
See p.303
• AMINO ACIDS are the building blocks
of proteins.
DNA Transcription
• DNA can “unzip”
itself and RNA
nucleotides match
up to the DNA
strand. See p.301
• Both DNA & RNA
are formed from
NUCLEOTIDES and
are called NUCLEIC
acids.
DNA Translation
• The cell uses
information from
“messenger” RNA
to produce proteins
See p.304-305
We will
discuss details
of this on a
later date
Types of Nitrogen Base Pairs
DNA
RNA
1.Adenine w/ 1.Uracil
w/adenine
thymine
2.Cytosine
2.Cytosine w/
w/guanine
guanine
CAUGCA
Transcription/Translation Quiz
1. identify the amino acids coded for by
these codons:
UGGCAGUGC
ACCGUCACG
1. Why is transcription necessary?
Transcription SIGNALS messenger RNA
(mRNA) to carry the code for proteins out of
the nucleus, to the ribosomes in the
cytoplasm.
2. Describe transcription.
RNA polymerase binds to DNA, separates the
strands, then uses one strand as a template to
assemble MRNA.
3. Why is translation necessary?
Translation assures that the right amino acids
are joined together by peptides to form the
correct protein.
4. Describe translation.
The cell uses information from MRNA to
produce proteins.
5. What are the main differences between
DNA and RNA.
DNA has deoxyribose, RNA has ribose;
DNA has 2 strands, RNA has one strand;
DNA has thymine, RNA has uracil.
6. Using the chart on page 303, identify the
amino acids coded for by these codons:
UGGCAGUGC
tryptophan-glutamine-cysteine
7. WHAT ORGANELLES ARE INVOLVED
IN TRANSCRIPTION?
AMAZING DNA FACTS…
• DNA from a single human
cell extends in a single
thread for almost 2 meters
long!!!
• It contains information
equal to some 600,000
printed pages of 500 words
each!!!
(a library of about 1,000 books)
LET’S REVIEW DNA…
LM p.44
1. List the conclusions Griffith & Avery,
Hershey & Chase drew from their
experiments.
2. Summarize the relationship between
genes & DNA.
3. Describe the overall structure of the
DNA molecule.
4. What are the 4 kinds of bases?
Reading Questions:
1. Are RNA Polymerase the same as DNA
polymerase?
2. What role do “Promoters” have in
transcription?
3.
SNORK ACTIVITY
DIRECTIONS
• TURN TO THE “DNA, RNA & SNORKS”
PAGE IN PACKET:
• READ THE 2 PARAGRAPHS ABOVE
THE TABLE, AND THE 3RD PARAGRAPH
BELOW THE TABLE.
AUA, UCG, GGC, UAU