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DNA Scientists Notes Pg. 1 & 2 (pg. 326-331 in textbook)
People
Griffith
_________
(British)
Avery
_________
(Canadianworked in USNew York)
Hershey &
Chase
________
(American)
Chargaff
_______
(American)
Franklin
_________
Watson
(American)
&
Crick
(British)
__________
Studying
Better way to fight
______________
Experiments
Conclusions
________ bacteria=dead mouse
_______ bacteria = alive mouse
Heat killed smooth= ______ mouse
Heat killed live + rough=_____
mouse
Some molecules or group
of molecules changed the
_________ __________
bacteria into deadly
smooth bacteria. Called
_________________
Studied DNA using
________________
Repeated above experiment:
Treated heat-killed smooth with
______________ that destroyed
either proteins, lipids,
carbohydrates, RNA. None affected
________________. When
_______ was destroyed
transformation was _________.
_________________- virus infects
bacteria. Knew viruses made of
____________ & _____. Used
____________ ______________ to
mark them Protein-sulfur-35, DNAphosphorus-32 Found phosphorus32 in bacteria
Showed that there was the same
amount of ____________ &
___________, and _________ &
___________
Powerful x-ray beams is aimed at a
sample, ten the scattering pattern
of the x-ray is recorded on the film
What is the
____________ of
DNA?
Analyzed other scientists’ work.
Few weeks after ___________ xray experiments- they solved the
puzzle of the structure of DNA.
Process of
_______________ as
a key to finding
heredity
Skeptical of
____________
conclusion. Wanted
more support
Studied __________
composition in ____
What held the two
strands together?
Made sketches & built models
____________ are made
of ____________
Bacteriophage
___________________
___________________
Chargaff’s rule: Always!!
_________
_________
By itself ___________
___________ the structure
of DNA
Two ______________
___________ around one
another
__________________
_______________
__________ between the
bases
Won Nobel Prize in 1962:
*1962-Watson & Crick- __________________________________
*1960- Brenner-_____________________________
*1977- Gilbert, Maxam, & Sanger- ___________________________________
*2000- ______________________________________- sequence all human DNA is nearly complete
DNA MODEL
Pg. 3-4
Nucleotides consist of :
1)Phosphate Group
2)5 Carbon sugar deoxyribose
3)A nitrogen base
-Weak Hydrogen bonds join nucleotides between nitrogen bases
-Strong Stable Covalent bonds holds each part of the nucleotide together.
The 4 Bases of DNA
• (A)denine
-(C)ytosine
• (T)hymine
- (G)uanine
These chains form a DOUBLE HELIX (like a twisted ladder)
Only specific pairs of bases bond together
A bonds to T
(Ash Tray / Garbage Can)
C bonds G
EX: A – T
C–G
G-C
Role of DNA
• Chromosomes are formed of genes
• Genes are segments of DNA which are the units of heredity.
DNA controls the development of traits and cellular activities
Pg. 5
DNA REPLICATION
The pairing of bases in complementary chains of nucleotides
• Before Cells divide, DNA has to copy itself, which is called…
DNA Replication.
• During this process DNA is in the form of Chromatin (DNA
wrapped in protein)
• There are many “free” nucleotides found in the nucleus of a
cell
• These “free” nucleotides act as building blocks for new DNA
STEPS OF DNA REPLICATION
1) Double helix untwists, enzyme “Helocase” breaks the H bonds, 2
nucleotide chains begin to separate like a zipper.
2) Each ½ serves as a pattern for the formation of a new DNA chain.
3) Free nucleotides in the nucleus join with the correct bases. (Chargaff’s BASE PAIRING RULE)
4) The enzyme DNA polymerase bonds the phosphates and sugars of the nucleotide together.
5) 2 new molecules of DNA (each contain an original & a new strand) become twisted and take the form of a
Double Helix
The 2 new DNA molecules are now called “Sister Chromatids” and remain stuck together until the cell
divides.
Uncoiling - unzipping -- adding new parts - 2 DNA molecules - recoiling
Page 7 (pg. 244-255 in textbook)
 Limits to Cell Growth- 2 main reasons cells divide rather than continuing to grow indefinitely:
– More Demands on DNA When cell increases in size it does not make extra copies of DNA
 If cell grew without limits “information crisis” would occur.
– Exchanging Materials Food, oxygen, & water have to enter the cell through the cell membrane
 Waste products have to leave
 The rate at which this exchange takes place depends on the surface area of the cell (total
area of the cell membrane)
 Ratio of Surface Area to Volume
– Volume increases more rapidly than the surface area
– Therefore, ratio of surface area to volume decreases
This decrease causes serious problems for the cell
– If too large becomes to difficult to get enough oxygen and nutrients in and wastes out
This is why cells do not grow much bigger even if the organism of which they are a part of does.
Page 8- Draw the Cell Cycle
 Cell Growth
 Describe:






Add Color!
G1- period of activity
in which cells do most
of their growing. Cells
increase in size and
synthesize new proteins
and organelles
S- Chromosomes are
replicated and synthesis
of DNA molecules takes
place
G2- Many organelles
and molecules required
for cell divisions are
produced
M phase- Mitosis
C phase- Cytokinesis
G0 phase-rest period
Page 9
 Draw, label, & describe the phases of:
 Interphase
 Prophase
Add Color!
Page 10
 Draw, label, & describe the phases of:
 Metaphase
 Anaphase
Add Color!
Page 11
 Draw, label, & describe the phases of:
– Telophase
– Cytokinesis- for both plant & animal
Add Color!
Page 12
Regulating the Cell Cycle:
Cell cycle regulators– early 1980’s biologists found a protein that increased & decreased the time with the cell cycle
– They called it cyclin because it seemed to regulate the timing of the cell cycle
– Since, they have discovered a whole family of cyclin proteins
Two types of Regulator Proteins
1. Internal Regulators- proteins that respond to events inside the cell
– Allows cell cycle to proceed only when certain processes have occurred inside the cell
– Ex: doesn’t let the cell enter mitosis until all chromosomes have been replicated
2. External Regulators- Proteins respond to events outside the cell
– Direct cells to speed up or slow down cell
– Ex: Growth factors- stimulate growth & cycle division of cells. Important in embryonic cells &
wound healing
Page 13
Uncontrolled Cell Growth
Cancer- disorder in which some of the body’s own cells lose the ability to control growth.
Cancer cells do not respond to the signals that regulate the growth of most cells, they divide uncontrollably &
form masses of cells called tumors that can damage surrounding tissue.
Two types of tumors:
1. Benign- does not spread to surrounding tissue (non-cancerous)
2. Malignant- Spreads & destroys healthy tissue (cancerous)
Causes:
1. Biological Agent- viruses
2. Chemical Agent- carcinogens- tobacco
3. Physical Agent- radiation
Treatments:
1. Surgery
2. Radiation
3. Chemotherapy
Page 14
1. Make a key:
a. A- _________________
d. G-_________________
b. T-__________________
e. S-_________________
c. C-_________________
f. P-_________________
2. What is the monomer of DNA. ___________________
3. What is the shape of DNA? __________________________________________
4. Who determined this shape? __________________________________________
5. a. Name the bond between the S & P ____________________________
b. Name the bond between the S & A ____________________________
c. Name the bond between the A & T ____________________________
6. What is DNA replication?
___________________________________________________________________
7. Where does DNA unzip during replication?_________________________________________________
8. What unzips it? _____________________
9. What is the end product of DNA replication? _____________________________________________
10. List the steps of DNA replication in order.
11. List the three parts of a nucleotide