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Molecular Biology:
DNA & Protein Synthesis
Ch. 8
Honors Biology
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History of DNA Research
1) _________ (1928)- discovered harmless
bacteria could be made harmful when mixed
with another bacteria that causes disease
through a process called “________________”
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History of DNA Research
2) _______ (1944)- discovered ______ was
responsible for transformation
3) ______________ (1952)- their studies
supported Avery’s work by studying
____________ (a virus that infects
bacteria)
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Hershey & Chase Experiment
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History of DNA Research
_______________ (1953)- first to develop a
3-D double helix model of _______
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DNA Structure
• DNA is made up of ____________.
• A nucleotide contains ____ parts:
1) ___________ group
2) _____________ group (deoxyribose)
3) ____________ (4 types)
- adenine (A)
- guanine (G) _________(double rings)
- cytosine (C)
- thymine (T) ____________ (single ring)
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Purines & Pyrimidines
• ______________
• ______________
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Chargaff’s Rule
• _________(1949) discovered the
base-pairing rules for nitrogen bases:
1) ____ always pairs with___ (________)
____ always pairs with ___ (________)
2___________ in DNA= __________ in DNA
% (A+G) = % (C+T)
%__ = % ___ , % __ = % ____
Ex. If C is 30 %, then determine % for A, T, G.9
DNA Structure
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Double helix
• DNA is a _________ composed of ____ long
strands of nucleotides twisted and held together
by ____________ in the center between the
nitrogen bases. A ______________ backbone is
on the outer part for each strand of DNA.
• Purines base pair with ____________.
DNA vs. RNA
• DNA (Deoxy-ribonucleic
Acid)
• _______ stranded
• A, G, C,T(_________)
(A–T, C-G)
• 1 type
• __________ sugar
(Missing an oxygen)
• RNA (Ribonucleic Acid)
• _______ stranded
• A, G, C, U (________)
(A-U, C-G)
• 3 types (mRNA, tRNA,
rRNA)
• ________ sugar (No
missing oxygen)
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3 Types of RNA
1) ______ (messenger RNA)
-copy the genetic information of _______
and carries it to ____________
2) ______ (transfer RNA)
- transfer ____________ to make ________
3)_______ (ribosomal RNA) - make up
__________
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DNA Replication (DNA -> DNA)
• DNA makes an identical copy of itself.
• takes place inside the ________ before _____
_________(during _______ of _________).
• ___________ unwinds DNA and ________
_____________ (enzyme) makes new strands of
DNA.
DNA Replication
(_________________)
• _________ replication
(1 ____ strand and 1
____strand in each
DNA after it
replicates.)
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True or False.
1.
2.
3.
4.
5.
DNA is made up of nucleotides.
DNA has a ribose sugar.
DNA is longer than mRNA.
Adenine pairs up with thymine in DNA.
Covalent bonds hold two nitrogen bases
together.
6. DNA structure was discovered by Watson and
Crick.
7. Adenine and Thymine are purines.
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Molecular Biology
• DNA --- RNA
--- Protein
________
________
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DNA
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Transcription & Translation
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1. Transcription
- _______ is copied onto _____ because DNA
cannot leave the nucleus
- occurs inside the _________.
Steps of Transcription
1) DNA molecule unwinds by enzymes (________)
2) An enzyme named _________ makes mRNA, a
copy of DNA, using the base-pairing rule
3) _______ leaves nucleus and travels to
__________ for protein synthesis.
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2. mRNA modification
* occurs before __________________________ after
______________________.
• During transcription, ________ are cleaved and
removed, while _______ combine to form useful
mRNA. Only ________ exit the nucleus.
initial mRNA

introns (_____________________ = junk DNA) cleaved

exons (___________________ = code for AA) combine

final mRNA
http://www.execulink.com/~ekimmel/mrna_flash.htm
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3.Translation/Protein Synthesis
(mRNA -> Protein)
• translate the ________ codes on ______ to
make _______________.
• occurs in ___________.
• each protein is made up of ________________.
• mRNA is translated in base triplets called
________ which represents an ____________.
• 3 nitrogen bases on mRNA(1 ________)
= 1 _____________
• Use genetic code table to determine which
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____________ each ________represents
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Why a codon can not be one or two
nitrogen bases long?
Not enough combinations to cover all __
amino acids.
1 nitrogen base long = __ amino acids
2 nitrogen bases long = __ a.a.
3 nitrogen bases long = __ a.a.
Having more than one codons (esp. the third
letter of a codon) for each amino acid
minimizes a mistake in transcription
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Steps of Translation
1) ______ leaves nucleus & travels to _________.
2) ______ is attached to ribosome. _____ carries its
specific _________and arrives at the ribosome
when _______ contains a _______ codon (AUG).
3) tRNA’s _________ base-pair with mRNA’s ______
and releases its amino acid.
4) Amino acids form _________ bonds to combine in
order to make a ________.
5) _______ continue moving down the ______ strand
and transferring amino acids until a ______ codon
is reached.
STOP codons: __________________
6) ______ is released from ribosomes. A _________
or a protein is formed.
Translation/Protein Synthesis
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Codon Vs. Anticodon
• Anticodon on ______
matches the codon on
__________.
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Transcription and Translation
Genetic Code
• All living things have ______ genetic code.
Ex. ACC in human codes for _______ amino acid as in
ACC in your dog or an oak tree.
• Different ______________-> different ___________->
distinct __________
• The __________________ of different proteins
determines the _________ characteristics of a living
thing.
True or False
1. A codon is found on tRNA.
2. Transcription occurs in the cytoplasm
near the ribosomes.
3. Transcription precedes translation.
4. All living organisms have same genetic
code.
5. Translation is also known as protein
synthesis.
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Mutation
• Definition: any change in _____ sequence
• Mutations in ________cells are
inheritable, but mutations in ______ cells
are not.
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What causes mutation?
___________
- any substance that causes mutation
– radiation (________________________),
chemicals, high temperature
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Types of Mutation
1. DNA change
a. ____________
- _______________ of one nitrogen base(s)
Ex. The big dog bit the man.
The big dog hit the man.
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Types of Mutation
b.____________ mutation
- ___________ or ___________ of nitrogen
base(s)
- Changes the ______________.
- More fatal than __________________.
- A different _______ is produced & most likely it
is NOT functional.
Ex. The big dog bit the man.
The xbi gdo gbi tth ema n. (insertion)
The bid ogb itt hem an (deletion)
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Types of Mutation
2. Chromosomal mutation
-few of these mutations are passed on the next generation
b/c the ___________ (fertilized egg) usually cannot
survive. If the zygote lives and fully develops, the
mature organism is often _________.
a. __________
ABCDE  ACDE
b. __________
ABCDE  ABABCDE
c. __________
ABCDE  ABDCE
d. ___________
ABCDE  ABCDEUVX
UVXYZ
YZ
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DNA and Protein Relationship
• The mistakes in ________ will lead to
mistakes in ___________ sequence.
• This will result in _________________
and people could be ill because the
defective proteins are not ___________.
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Protein folding
* The length of proteins
varies and the sequence of
_________ determines
how proteins ____ b/c
some a.a. are attracted to
each other and some
repel.
*How proteins get folded
determines its _____
______ & its ________.
Why is your brain cell different from your skin cell
even though they are from same original cell?
• ____________________
Cells become specialized in
structure & function.
• _____________________
Genes could be turned “on”
and turned “off”.
Genes are ____________ =
____________ are made.
Different genes are
________ or ________ in
different type of cells.
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Lac Operon (in bacteria)
• Has 3 genes that code for enzyme lactase.
• _______ breaks down ______ sugar in
milk.
• ________ – includes promoter, operator
and gene(s) for a specific protein.
• ________ – helps RNA polymerase find
where a gene starts.
• ________ – a DNA segment that turns the
gene(s) “on” or “off”.
The Lac Operon (in bacteria)
The ___________ IS bound to the __________.
Transcription is blocked b/c RNA polymerase can’t bind
to the ________. The genes are turned “______”
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Regulation of Gene Expression
• Lac operon (in bacteria)
__________ binds to the
_____________ and the
repressor comes off the
______________ site.
When the __________ is NOT
bound to the _______ site,
_______________ binds to
promoter site and starts
________________.
The genes are turned “____” &
expressed. _________
(enzyme protein) is
produced.
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Eukaryotic Gene Expression
• More complex.
• Needs _______ _________ in order for
_____ ____________to start transcription.
• Also enhancers and silencers can regulate
the rate of transcription of gene.