Unit 6 DNA & The Cell Cycle
Test date 11-9
GENETIC MATERIAL
In the middle of the 1900’s scientists were asking questions about genes.
What is a gene made of?How do genes work?How do genes determine characteristics of organisms?
DO PROTEINS CARRY THE GENETIC CODE?
At the time most scientists believed that _________ had to be the molecules that made up genes.
There were so many different kinds proteins and DNA seemed to be too monotonous . . . repeating the same ___ subunits. 4
proteins
SEE GRIFFITH’s EXPERIMENT1928 – Frederick Griffith looked atpneumonia bacteria trying tofigure out what made people die
Images from: http://microvet.arizona.edu/Courses/vsc610/mic205/griffith.jpg
S (SMOOTH) strain- killed mice
R (Rough) strain-mice lived
If he heated the LETHAL strain first
_______________
Images from: http://microvet.arizona.edu/Courses/vsc610/mic205/griffith.jpg
The heat killed bacteria were no longerLETHAL.
Heat killed + live rough = dead mouse
. . . mice lived.
Griffith called this process __________________ because one strain of bacteria had been changed permanently into another.
But what was the factor that caused thetransformation?
A protein ? A lipid ? A carbohydrate ?A nucleic acid ?
TRANSFORMATION
Griffith 1928 (British)
Studied: Better way to fight pneumonia
Experiments:
Smooth bacteria=dead mouse.
Rough bacteria = alive mouse.
Heat killed smooth= live mouse
Heat killed smooth + rough=Dead mouse
Conclusions: Some molecules or group of molecules changed the harmless rough bacteria into deadly smooth bacteria. Called transformation
1944-Oswald Avery’s team of scientistsrepeat Griffith’s experimentslooking for the transforming molecule.
After heat killing the LETHAL Pneumonia bacteria, he treated them with digestive enzymes that destroy specific kinds of molecules.
If proteins, polysaccharides, lipids, or RNA’s were destroyed .. .______________________________
http://cystitis-cystitis.com/Images/testtube.jpg
http://en.wikipedia.org/wiki/Oswald_Avery
http://faculty.uca.edu/~johnc/mbi1440.htm
Transformation still occurred!
But when they treated the heat-killedLETHAL bacteria with enzymes todestroy _____ there was NOtransformation! . . . the mice lived!
DNA was the moleculethat caused the genetic change.
DNA
http://web.jjay.cuny.edu/~acarpi/NSC/12-dna.htm
GRIFFITH EXPERIMENT (PNEUMONIA-RAT)
Showed ____________ could bepassed between bacteria & cause achange.
AVERY EXPERIMENT (Digestive enzymes)
showed that the genetic material was _____DNA
genetic material
Avery 1944
Studying: Process of transformation as a key to finding heredity
Experiments: Repeated above experiment: Treated heat-killed smooth with enzymes that destroyed either proteins, lipids, carbohydrates, RNA. None affected transformation. When DNA was destroyed transformation was blocked.
Conclusions: Genes are made of DNA
Scientists are skeptical… it takes more than one experiment to convince them.
1952-Alfred Hershey and Martha Chaseexperimented with viruses that infect bacteria = _________________
Knew bacteriophages were made of ________ and _______
bacteriophages
http://www.mun.ca/biology/scarr/Chase_&_Hershey_1953.jpg
Hear about their
cool experiment
proteins DNA
http://www.mun.ca/biology/scarr/hersheychase-experiment.jpg
HERSHEY-CHASE BLENDER EXPERIMENT
Showed_______________ entered cell during infection.
Conclusion:______________in virus was_____ not protein
only DNA not protein
Genetic material DNA
BACTERIAL VIRUSES
http://faculty.uca.edu/~johnc/mbi1440.htm
Hershey & Chase 1950
Studying: Skeptical of Avery’s conclusion. Wanted more support
Experiments: Bacteriophage- virus infects bacteria. Knew viruses made of protein & DNA. Used radioactive isotopes to mark them Protein-sulfur-35, DNA-phosphorus-32 Found phosphorus-32 in bacteria
Conclusions: Genetic material is DNA, not protein
Chargaff 1950
Studying: Studied nucleotide composition in DNA
Experiments: Showed that there was the same amount of adenine & thymine, and cytosine & guanine
Conclusions: Chargaff’s rule: Always!! A-TC-G
(Ash Tray / Garbage Can)
DNA is a DOUBLE HELIXhttp://en.wikipedia.org/wiki/Rosalind_Franklin
http://www.time.com/time/time100/scientist/profile/watsoncrick.html
X-ray experiments by Rosalind Franklin led James Watson and Francis Crick to thediscovery of the structure of DNA in 1953
Franklin 1951
Studying: Studied DNA using
x-ray diffraction
Experiments: Powerful x-ray beams is aimed at a sample, ten the scattering pattern of the x-ray is recorded on the film
Conclusions: By itself does not reveal the structure of DNA SHE WAS CHEATED OUT OF THE PRIZE!!!
Watson & Crick 1953
Studying: What is the structure of DNA? What held the two strands together?
Experiments: Analyzed other scientists’ work. Few weeks after Franklin’s x-ray experiments- they solved the puzzle of the structure of DNA. Made sketches & built models
Conclusions: Two strands twisted around one another Double Helix
Hydrogen bonds between the bases
DNA REPLICATION
Prior to _________, the DNA must ______. DNA can replicate itself exactly due to ___________Replication occurs in the ________of the cell and requires the participation of several _________.
cell division
replicate
Chargaff’s rules
nucleus
enzymes
Summary of DNA Replication
1. Enzyme _______“unzips” DNA by breaking the _________ bonds between the______________.
Where unzipping begins is called the__________________; the continuation of unzipping is the ______________, Occurs in several places in each _____________; like a ______________
2. __________________________ hold the separated DNA strands apart.
helicase
hydrogen
nitrogen bases
origin of replicationreplication fork
chromosome
broken zipper
Single-strand binding proteins
Summary of DNA Replication
3. ______________ adds nucleotides to both sides of the DNA molecule according to base pairing rules.
DNA polymerase has two restrictions:
a. it can only add nucleotides in a ______ direction
b. it can only add nucleotides to an existing strand.
DNA polymerase
5’ – 3’
Summary of DNA Replication4. Two sides of DNA are replicated differently because nucleotides can only be added in a _____________
_____________- side replicated in the ____________ as the replication fork. __________ are moved in by DNA polymerase in a 5’ – 3’ direction as the DNA is unzipped.
5’ – 3’ direction
Leading strand
same direction
Nucleotides
Summary of DNA Replication
____________- nucleotides are __________ from the replication fork. ______________ of nucleotides are synthesized, as the DNA is unzipped. These short segments are known as _______________. Eventually, the ____________ “glues” together the ________________to
create a continuous
strand of nucleotides
Lagging strand
added away
Short segments
Okazaki fragments
enzyme ligase
Okazaki fragments
Summary of DNA Replication
5. Another type of DNA polymerase _________ the replicated DNA to ________ the change of ________.
6. Results in ___________ DNA molecules, each consisting of one _______ strand and one ____ strand.
proofreads
minimize mutation
two identical
originalnew
Summary of DNA Replication
These two identical DNA molecules are the ______________ that proceed through _______
Once replication has
been completed, the
cell moves into ___
and then,
_________________.
sister chromatids
mitosis
G2
prophase of mitosis
Cellular Growth
The third statement of the Cell Theory states that all cells come from ______________. The continuity of life is based on the reproduction of cells or ___________ . In most organisms, cells increase to a certain size and then divide into two cells. This cycle of growth and cell division is known as the __________.
pre-existing cell
cell division
cell cycle
Cellular Growth
The cell cycle is defined as the period of time from the beginning of ___________ to the _____________________. This type of cell division is ________ reproduction. In asexual reproduction, the genome or _____ of the cell is exactly replicated resulting in ________________.
cell division
beginning of the nextasexual
DNA2 identical cells
I. IMPORTANCE OF ASEXUAL REPRODUCTION
A. Single-celled Organisms
Single-celled organisms like _______________ use asexual reproduction to ______________________________
bacteria & yeast
make new organisms-reproduce
I. IMPORTANCE OF ASEXUAL REPRODUCTION
B. Multicellular Organisms
1. Growth & Development – Organisms grow through ___________, rather than unlimited growth of a cell because if a cell gets too large, it cannot meet its own needs and maintain ____________. A cell grows to a certain size, and then it divides.
cell division
homeostasis
2. Renewal & Repair – Cell division is used to replace cells that die from normal wear & tear; for example, __________. Other types of cells maintain the ability to divide, but keep it in reserve unless severely damaged; for example, __________. Other cells do not appear to divide at all in a mature human; for example, ____________________________, although recent experimental findings appear to dispute this long-standing _______.
skin cells
liver cells
nerve cells, cardiac muscle cells
theory
II. Cell Size Limitations
Ratio of surface are to volume- As the cell grows, its volume (__________) increases much more rapidly than the surface area (______________). The cell will have difficulty supplying ___________________ enough waste products. By remaining small, cells have a _______ ratio of surface area to volume and can sustain themselves more easily.
cytoplasm
cell membrane
nutrients & expelling
higher
Surface Area (length
x width x 6)
Volume
(length x width x height)
Ratio of Surface Area to
Volume
Transport of substances- movement of substances within the cell managed more easily in a small cell vs. a large.
1. _________- diffusion over long distances is slow & inefficient because it relies on random movement
2. ______________- ____________ transportation network becomes
less efficient for a cell if the
distance to travel becomes
too large.
Diffusion
Motor Proteins cytoskeleton
Cellular Communications- Cell size affects the ability of the cell to communicate ____________ for cellular functions; if too large it becomes __________ for cellular communications. Ex. The signals that trigger protein synthesis might not reach the _____________ enough for protein synthesis to occur.
instructions
impossible
ribosome fast
CELL CYCLE IN PROKARYOTES (p. 252 & 520)
All ________ undergo a type of cell division known as _____________. Binary fission is a less complex, faster process than eukaryotic cell division because bacteria lack a ______________________________ and have only __ chromosome.
bacteria
binary fission
nucleus, membrane bound organelles
1
The Cell Cycle
The Cell Cycle
G1 Phase- (Gap 1) Cell is growing, carrying out normal cell functions & preparing to replicate DNAS phase- synthesis- the period when a cell copies its DNA in preparation for cell divisionG2 phase- (Gap 2) Cell is preparing for cell division
*Producing microtubules*Taking inventory
M phase- Mitosis
Interphase
Cell grows & carries out normal cell processDNA replicates
Prophase❑ Nuclear
membrane disintegrates
❑ Nucleolus disappears
❑ Chromosomes condense
❑ Spindle apparatus begins to form between the poles
Metaphase
Chromosomes attach to spindle apparatus & align along the equator of cell
Anaphase
Microtubules shorten, moving chromosomes to opposite poles
Telophase
➢ Chromosomes reach poles of cells
➢ Nuclear envelope reforms
➢ Nucleolus reappears
➢ Chromosomes decondense
Cytokinesis
Plant cell: Cell plate forms dividing daughtersAnimal cells: Cleavage furrow forms at equator of cell & pinches inward until cell divides in two
Normal Cell Cycle
The timing & rate of cell division are important to the health of an organism. The _________ of cell division varies depending on the type of cell
A. Cyclins (__________) & cyclin-dependent kinases (____________) (CDKs)- bind to each other to start various activities of the cell cycle. Ex. Signal start of cell cycle, ________________, protein synthesis, nuclear division & end of the ____________( different _____________for each)
rate
proteins
enzymes
DNA replication
Cell cycle
combination
Normal Cell Cycle
B. _____________- cell cycle built in checkpoints that __________ the cycle & can stop it if something goes wrong.
a. Checkpoint near end of G1 monitors for _____________& can stop the cycle before entering the S stage,
b. ________________checkpoints during S phase & after
c. _____________________if problem with spindle can stop before ____________
checkpoints
monitors
DNA damage
Quality control
Spindle checkpoints
cytokinesis
Abnormal Cell Cycle: Cancer (page 11 of booklet)
______________ is the uncontrolled growth & division of cells- a failure in the regulation of the cell cycle.
cancer
Causes of Cancer
Cellular- ________ occurs is not repaired by cell. cancer can result.Carcinogens-___________ & agents that are know to cause cancer. Include: tobacco, UV rays GeneticsBiological agents-__________________
mutations
substances
Bacteria & viruses
Apoptosis- (page 11 of booklet)
_____________ cell death.Cell going through will shrink & shrivel in a controlled process. Ex. During development of human _________________________Plants- localized death of cells results in leaves falling in autumnCells damaged beyond repair
Programmed
Hand and foot webbing
Stem Cells/Pluripotent-Page 11 of booklet
Stem cells or pluripotent cells-are __________ cells that can develop into _____________ cells with the proper ________ 2 types___________stem cells___________stem cells
unspecialized
specialized
signals
embryonic
adult
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