Download Chapter 13 DNA Structure and Function Johann Friedrich Miescher

Chapter 13 DNA Structure and Function
 Johann Friedrich Miescher
 Linus Pauling
 1953 Watson and Crick
 Fredrich Griffith
 1928 working with the ________________________________-causing bacterium
(__________strain - ______________________ and_____________ strain –
_____________________)
 Found that __________________________ was the causes the person to be sick
 Performed four experiments:
 Injected mice with R Cells – mice lived
 Injected mice with S Cells – mice died
 S Cells were heat-killed then injected then into mice; live S cells were found in the blood
 Griffith explanation – heated S strain did not have hereditary information it was destroyed
 Transformation:
 Conclusion
 Living bacteria acquired _____________________________ from dead bacteria - particularly the
instructions for making capsules, thus transforming the naked bacteria into incapsulated
bacteria.
 The Transforming agent was discovered to be _____________________. DNA was isolated and
added to live naked bacteria, and they were _____________________________ into the
incapsulated kind.

 Oswald Avery
 Hershey and Chase
 Used the ______________________________ (a virus) to show that viruses are composed of
DNA or RNA
 1. Hershey and Chase forced one population of phages to
________________________________ using radioactive phosphorous.
 2. The radioactive phosphorous "labeled" the DNA.
 3. They forced another group of phages to synthesize protein using radioactive sulfur.
 4. The radioactive sulfur "labeled" the ________________________________.
 5. Bacteria infected by phages containing radioactive protein did not show any radioactivity.
 6. Bacteria infected by phages containing ______________________________ became
radioactive.
 7. This showed that it was the __________________________, not the protein, that was the
molecule of heredity.
Experiment A
Experiment B
DNA contains
phosphorous but
not sulfur.
Proteins contain
sulfur but not
phosphorus

 DNA Structure
 DNA is composed of four kinds of nucleotides which consist of:
 One of four bases:
 Nucleotides are similar, but thymine and cytosine are single-ring
__________________________________; A and G are double ring ________________________
 __________________________________In 1949 found that the four kinds of nucleotide bases
making up DNA molecule differ in relative amounts from species and species
 Adenine =Thymine (How can I remember the base pairing?) ________________________ Cytosine=Guanine (How can I remember the base pairing?) ________________________

__________________________________________Used X-ray diffraction techniques
to produce images of DNA molecules
 __________________________ exist as a long, thin, molecule of uniform diameter
 Structure is highly____________________________
 DNA is ______________________________________ (twisted ladder)
 _____________________________________________
Used numerous
sources of data to build models of DNA
 Following features were
 Single-ringed thymine was ___________________________________ with double ringed
adenine and single-ringed cytosine with double ringed guanine, along the entire length of the
molecule
 Backbone was made of chains of __________________________________ linkages
 The molecule was double stranded and looked like a ladder with a twist to form a
___________________________________
 DNA Structure
 The _________________________________________ make up the "backbone" of the DNA
molecule.
 The phosphate is attached to the _______________________' carbon (the 5 is a number given
to sugar molecules). The DNA strand has a_____________________ phosphate on the 5' end,
and a free sugar on the ________________________end - these numbers will become
important later.
 DNA is composed of subunits called ____________________________________, strung
together in a long chain -- Each nucleotide consists of: a phosphate, a sugar (deoxyribose), and a
base
 The two sides of the helix are held together by _________________________________

 Nitrogen Bases
 DNA is composed of subunits called _____________________________, strung together in a
long chain -- Each nucleotide consists of: a phosphate, a sugar (deoxyribose), and a base
 Bases come in two types: _____________________________ (cytosine and thymine) and
____________________________ (guanine and adenine)


 DNA Replication
 Steps of DNA replication
 1. ______________________________ (enzyme) unwinds the DNA. The junction between the
unwound part and the open part is called a ___________________________.
 2. __________________________________ adds the complementary nucleotides and binds the
sugars and phosphates. DNA polymerase travels from the 3' to the 5' end.
 3. DNA polymerase adds __________________________ nucleotides on the other side of the
ladder. Traveling in the opposite direction.
 4. One side is the _________________________ - it follows the ______________________ as it
unwinds.
 5. The other side is the ___________________________ - its moving away from the helicase
 Problem: it reaches the replication fork, but the helicase is moving in the opposite direction. It
stops, and another polymerase binds farther down the chain.
 This process creates several fragments, called ________________________, that are bound
together by ___________________________________________.
 6. During replication, there are _______________________________ along the DNA that are
synthesized at the same time (multiple replication forks). It would take forever to go from one
end to the other, it is more efficient to open up several points at one time.


 Monitoring and Fixing the DNA
 ________________________________________________________ and other enzymes engage
in DNA repair
 DNA polymerase “_________________________________” the new bases for mismatched
pairs, which are replaced with correct bases