Download Unit 4: DNA: Our Genetic Material Notes

Unit 4: DNA: Our Genetic Material Notes
Date_______________________
I. Discovering DNA is hereditary material:
A. Griffith and Transformation
1. Griffith set up four individual experiments and in the final experiment:
Experiment 4: Griffith mixed his heat-killed, disease-causing bacteria with
live, harmless bacteria and injected the mixture into the mice.
(1) The mice developed pneumonia and _________??
Griffith concluded that the heat-killed bacteria passed their diseasecausing ability to the harmless strain.
3. Transformation
a. Griffith called this process transformation because one strain of bacteria
(the harmless strain) had changed permanently into another (the diseasecausing strain).
b. Griffith hypothesized that a factor must contain information that could
change harmless bacteria into disease-causing ones
B. Avery and DNA
1. Avery and his colleagues made: an extract from the heat-killed bacteria thymes.
a. The enzymes destroyed:
ncluding the nucleic acid RNA.
b. Transformation:ill occurred.
c. When DNA was destroyed, transformation did not occur.
e. Avery and other scientists discovered that the nucleic acid DNA the next.
C. The Hershey-Chase Experiment
1. Bacteriophage viruses are composed of a: DNA or RNA core and a protein coat.
2. To determine whether or not the molecule injected by viruses to cause
transformation was _____________ or _________--Scientists grew viruses in
Unit 4: DNA: Our Genetic Material Notes
Date_______________________
cultures containing radioactive isotopes of phosphorus-32 (32P) and sulfur-35
(35S).
a. Nearly all the radioactivity in the bacteria after viral transformation was
from_____________from phosphorus (32P).
d. Hershey and Chase concluded that :
FUNCTION of DNA:
DNA contains the ______________, or instructions for building an organism and
____________that ensure that organisms function correctly. It is necessary for the formation
of proteins/protein synthesis.
II. Structure of DNA
A. DNA is a very long polymer.
1. The basic shape is like a twisted ladder or zipper also called a double helix.
2. Contains two strands (backbones) composed of deoxyribose sugar and a phosphate
group.
3. The ___________, ________________“rungs” of the ladder are composed of
nitrogenous bases
B. The Components and Structure of DNA
1. DNA is made up of monomers called ___________.
Finish diagraming figure to the right and label the parts:
a. Deoxyribose – 5-carbon Sugar
b. Phosphate Group
c. Nitrogenous Base
(1) There are four kinds of bases in DNA:
ymine
C. Chargaff's Rules
Unit 4: DNA: Our Genetic Material Notes
Date_______________________
1. Chargaff discovered that the percentages of guanine [G] and cytosine [C] bases are
almost equal in any sample of DNA and the percentages of adenine [A] and thymine [T]
are almost equal in any sample of DNA. Therefore the _____________ rule must be:
2. Two types of nitrogenous bases:
a. Purines (double ringed bases)
b. Pyrimidines (single ringed bases).
3. Watson and Crick discovered that h
a. Adenine and thymine form two hydrogen bonds between each other
b. Guanine and Cytosine form three hydrogen bonds between each other.
c. This principle is called __________ __________ . The ________
_________ rule
*circle and label one monomer of DNA on
the molecule pictured below and the right:
D. X-Ray Evidence
1. Rosalind Franklin used X-ray diffraction to get information about
the structure of DNA.
2. She aimed an X-ray beam at concentrated DNA samples and
recorded the scattering pattern of the X-rays on film.
3. Using clues from Franklin’s pattern, James Watson and Francis
Crick built a model that explained how DNA carried information
and could be copied.
4. Watson and Crick's model of DNA was a double helix, in which
two stra other.
E. Arrangement of the DNA strands.
1. The two strands making up DNA are antiparallel.
a. The DNA strand end that ends with a phosphate
groups is called the 5’ end.
Unit 4: DNA: Our Genetic Material Notes
Date_______________________
b. The DNA stand end that ends with a sugar is called the 3’ e billion
meters)
III. DNA Replication
A. Before a cell divides, during __ phase of the cell _____________ DNA is ____________or
_______________to ensure f DNA.
B. Each strand of the DNA double helix has all the information needed to reconstruct the other
half by the mechanism of base pairing.
C. In most prokaryotes, DNA replication begins at a single point and continues in two
directions.
D. In eukaryotes, DNA replication occurs at hundreds of places. Replication proceeds in both
directions until each chromosome is completely copied.
1. A series of enzymes play a major role in DNA replication
2. Step 1: DNA Helicase opens the double helix by breaking the hydrogen bonds that link
the nitrogen bases between two strands
a. Creating a replication fork _________________________________________________________. Now
draw the picture of the replication fork: rea where the double helix
separates.
3. Step 2: At the replication fork, enzyme known as DNA polymerase moves along each of
the DNA strands and adds nucleotides to the exposed bases.
a. Nucleotides are added in a 5’ to 3’ direction only.
b. Nucleotides are added on both strands of the “parent” DNA molecule.
c. While the “new” DNA molecules is being assembled theb
4. Step 3: DNA polymerase proofreads the replication.
a. Reduces errors in replication to about 1 error per billion nucleotides.
Unit 4: DNA: Our Genetic Material Notes
Date_______________________
5. Replication is considered to be:
_______________________________________because:emi-conservative.
a. Each “parent” strand is complementary paired with a “daughter” strand
Place the following terms in the correct place on the above figure: DNA Polymerase (shown
twice) and Helicase. Then identify the original “parent strand of each new DNA molecule.