Name:____________________________________ Date:____________ Period:____
Chapter 12 Overview
Section 1: DNA: The Genetic Material
Section 2: Replication of DNA
Section 3: DNA, RNA, and Protein
Section 4: Gene Regulation and Mutation
Note: 1869 - Frederick Miescher discovered DNA, was acidic molecule in nucleus; called it
NUCLEIC ACIDS.
12.1 DNA: The Genetic Material
Fredrick Griffith
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Performed the first major experiment that
led to the discovery of DNA as the
______________
____________________
The First demonstration of bacterial
_______________________.
Experiments done by Frederick Griffith (in
London) in 1928 found there were two
different types of the bacterium
Streptococcus pneumoniae:
• An "S" or _______________ coat strain, which is lethal to mice.
• An "R" or _______________ strain, which will not hurt the mouse.
– Griffith found that he could heat ___________________the smooth strain.
However, if he were to take a mixture of the heat-inactivated S strain, mixed with the R strain,
the bacteria would die.
Thus there was some material in the ___________________ S strain that was responsible for
"transforming" the R strain into a lethal form.
Fredrick Griffith (and a lab co-worker) was killed in their laboratory in 1940 from a German
bomb.
Griffith’s work continued in U.S.
•
•
in 1944, Oswald Avery, C.M. MacLeod, and M. McCarty carefully demonstrated that the
___________ material that was responsible for the transformation was DNA
Thus, DNA was the "Genetic material" - however, many scientists were still not sure that it was
REALLY DNA (and not proteins) that was the genetic material.
Oswald Avery
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Identified the molecule that transformed the R strain of bacteria into the S strain
Concluded that when the S cells were killed,________________________
R bacteria incorporated this ____________ into their cells and ______________ into S cells.
Hershey and Chase (1952)
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Used _______________________ labeling to trace the DNA (P) and protein (S)
Concluded that the ____________ DNA was injected into the cell and provided the genetic
information needed to produce new viruses
Ch. 12 Notes Page 1
12.1 Table Summary of Hershey-Chase Results
Group 1 Viruses labeled with 32P
Infected
Bacteria
Liquid with
Viruses
Group 2 Viruses labeled with 35S
Infected
Bacteria
Liquid with
Viruses
Chargaff’s rule: C = G and T = A
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In 1950, Erwin Chargaff analyzed the base composition of DNA in a number of organisms.
Purines = _________________________; Pyrimidines = ____________________________
He reported that DNA composition varies from one species to another.
Such evidence of molecular diversity, which had been presumed absent from DNA, made DNA a
more __________________ candidate for the genetic material than protein.
X-ray Diffraction Structure Analysis (1951-1952)
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X-ray diffraction data helped solve the structure of DNA
Indicated that DNA was a _________________________
This is the famous ______________________ - Picture 51
which is believed to have been leaked to James Watson and
Francis Crick by Maurice Wilkins.
X-ray Diffraction Rosalind Franklin (1920 - 1958)

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The technique with which Maurice Wilkins and Franklin set
Sodium deoxyribose nucleate from calf thymus,
out to do this is called ____________________________.
Structure B, Photo 51, taken by Rosalind E.
Franklin and R.G. Gosling (her student). Linus
With this technique a crystal is exposed to x-rays in order
Pauling's hologrphic annotations are to the right
to produce a diffraction pattern.
of the photo. May 2, 1952
If the crystal is pure enough and the diffraction pattern is
______________very carefully, it is possible to
reconstruct the _______________of the atoms in the molecules that comprise the basic unit
of the crystal.
Rosalind Franklin died from ______________ in April of 1958, at the age of 37.
Ch. 12 Notes Page 2
James Watson and Francis Crick 1953

Built a model of the double helix that conformed to the others’ research
1. two outside strands consist of alternating _____________________ and
_______________
2. _______________ and ______________ bases pair to each other by three hydrogen bonds
3. ________________and ______________ bases pair to each other by two hydrogen bonds
Nobel Prize in Medicine/Physiology
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•
•
The rules of the Nobel Prize forbid posthumous nominations; because ____________________
had died in 1958 she was not eligible for nomination to the Nobel Prize subsequently awarded to
Francis ____________, James _______________, and Maurice ______________ in 1962.
The award was for their body of work on nucleic acids and not exclusively for the discovery of
the structure of DNA.
By the time of the award Wilkins had been working on the structure of DNA for over 10 years,
and had done much to confirm the Crick-Watson model. Crick had been working on the
_______________________ at Cambridge and Watson had worked on ____________ for
some years.
DNA Structure – Double Helix
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DNA often is compared to a twisted
ladder.
Rails of the ladder are represented by
the alternating __________________
and phosphate.
The pairs of bases (cytosine–guanine or
thymine–adenine) form the steps.
Orientation
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On the top rail, the strand is said to be oriented 5′ to 3′.
The strand on the bottom runs in the opposite direction and is oriented 3′ to 5′.
Chromosome Structure
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DNA coils around _________________ (proteins) to form ___________________, which
coil to form chromatin fibers.
The chromatin fibers supercoil to form
____________________ that are visible in the
metaphase stage of mitosis.
12.2 Replication of DNA
Semiconservative Replication
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Parental strands of DNA separate, serve as
_________________, and produce DNA molecules
that have ___________________ of parental
DNA and_________________ of new DNA.
Ch. 12 Notes Page 3
Unwinding
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_____________________, an enzyme, is responsible for unwinding and unzipping the double
helix.
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_________________, an enzyme, adds a short segment of RNA, called an __________
_____________, on each DNA strand. Keeping the DNA strands separate.
Base pairing
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DNA polymerase (an enzyme) continues adding appropriate nucleotides to the chain by adding to
the 3′ end of the new DNA strand.
One strand is called the _____________________ and is elongated as the DNA unwinds.

Leading Strand is synthesized ________________
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The other strand of DNA, called the _______________________, elongates away from the
replication fork.
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The _____________________________ is synthesized discontinuously into small segments,
called Okazaki fragments
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Joining
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____________________________ removes the RNA primer and fills in the place with DNA
nucleotides.
___________________ links the two sections.
Write a summary of replication in your own words
Comparing DNA Replication in Eukaryotes and Prokaryotes
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Eukaryotic DNA unwinds in multiple areas as DNA is ____________________.
In _______________________, the circular DNA strand is opened at one origin of
replication.
Ch. 12 Notes Page 4
12.3 DNA, RNA, and Protein
Central Dogma: _______________________________
RNA
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Contains the sugar ribose (instead of deoxyribose) and the base uracil (instead of thymine)
Usually is single stranded
Three kinds: messenger RNA, transfer RNA, and Ribosomal RNA
1. ___________________________ (mRNA)
a) Long strands of RNA nucleotides that are formed complementary to one strand of
DNA
b) Carries genetic information from DNA in the _____________________ to direct
protein synthesis in the _____________________
2. ___________________________ (rRNA)
 Associates with proteins to form ribosomes in the cytoplasm
3. ___________________________ (tRNA)
 Smaller segments of RNA nucleotides that transport amino acids to the ribosome
where proteins are made by adding one_____________________ at a time
Transcription
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Through
__________________,
the DNA code is
transferred to mRNA in
the nucleus.
DNA is unzipped in the
_____________ and RNA
polymerase binds to a
specific section where an
mRNA will be synthesized
RNA Processing
The code on the DNA is interrupted periodically by sequences that are not in the final mRNA.

Intervening sequences are called __________ – these are ____________.

Remaining pieces of DNA that serve as the ______________ sequences are called _________.
The Code
Experiments during the 1960s demonstrated that the DNA code was a three-base code.
The three-base code in DNA or mRNA is called a ________________.
The 1968 Nobel Prize in Medicine was awarded to Robert W. Holley, Har Gobind Khorana, and
Marshall W. Nirenberg for deciphering the Genetic Code. The code is used by cells to translate
messenger RNA sequences into protein. The mRNA sequence is read three bases at a time in codons.
Each ____________ identifies a specific ________________ or a _______________________.
Ch. 12 Notes Page 5
Translation
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In translation, tRNA molecules act as the
interpreters of the mRNA codon sequence.
At the middle of the folded strand, there is a
three-base coding sequence called the
_____________________.
Each anticodon is____________________ to
a codon on the mRNA.
One Gene—One Enzyme
The Beadle and Tatum experiment showed that one gene codes for one enzyme. We now know that one
gene codes for one polypeptide.
12.4 Gene Regulation and Mutation
Prokaryote Gene Regulation
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Ability of an organism to control which genes are
transcribed in response to the environment
An _______________ is a section of DNA that contains
the genes for the proteins needed for a specific metabolic
pathway
1. __________________
2. __________________
3. __________________
4. ___________________
The Trp Operon
Ch. 12 Notes Page 6
The Lac Operon
Eukaryote Gene Regulation
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Controlling transcription
_____________________________ ensure that a gene is used at the right time and that
proteins are made in the right amounts
The complex structure of eukaryotic DNA also regulates transcription.
Hox Genes
Hox genes are responsible for the general body pattern of most animals.
RNA Interference
RNA interference can stop the mRNA from translating its message.
Mutations - A permanent change that occurs in a cell’s DNA is called a mutation.
Types of mutations
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Point mutation
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Insertion
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Deletion
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Frameshift
Protein Folding and Stability
Substitutions also can lead to genetic disorders. Can change both the folding and stability of the
protein
Causes of Mutation
1. Can occur spontaneously
2. Chemicals and radiation also can damage DNA.
3. High-energy forms of radiation, such as X rays and gamma rays, are highly ________________.
Body-cell (Somatic) v. Sex-cell Mutation
___________________ mutations are not passed on to the next generation.
Mutations that occur in ____________________ are passed on to the organism’s offspring and
will be present in every cell of the offspring.
Ch. 12 Notes Page 7
Review Questions
1.
Which scientist(s) definitively proved that DNA transfers genetic material?
2. Name the small segments of the lagging DNA strand.
3. Which is not true of RNA?
Which is true:
4. The experiments of Avery, Hershey and Chase provided evidence that the carrier of genetic information
is _______.
5. What is the base-pairing rule for purines and pyrimidines in the DNA molecule?
What are the purine bases ______________________________________
What are the pyrimidine bases ___________________________________
6. What are chromosomes composed of?
7. The work of Watson and Crick solved the mystery of how DNA works as a genetic code. True or False
8. Which is not an enzyme involved in DNA replication?
9. During DNA replication, what nucleotide base sequence is synthesized along an original strand that has the
sequence TCAAGC?
10. Which shows the basic chain of events in all organisms for reading and expressing genes?
11. In the RNA molecule, uracil replaces ___________________.
12. What does each diagram shows?
13. What characteristic of the mRNA molecule do scientists not yet understand?
Ch. 12 Notes Page 8
14. Why do eukaryotic cells need a complex control system to regulate the expression of genes?
15. Which type of gene causes cells to become specialized in structure in function?
16. What is an immediate result of a mutation in a gene?
17. Which is the most highly mutagenic?
18. Look at the following figure. Identify the proteins that DNA first coils around.
19. Explain how Hox genes affect an organism.
20. Explain the difference between body-cell and sex-cell mutation.
21. What does this diagram show about the replication of DNA in eukaryotic cells?
22. What is this process called?
23. What type of mutation results in this change in the DNA sequence? TTCAGG TTCTGG
24. How could RNA interference be used to treat diseases such as cancer and diabetes?
25. The structure of a protein can be altered dramatically by the exchange of a single amino acid for another.
True or False
Ch. 12 Notes Page 9