PreAP/GT Cell Cycle Notes 2015
Why Do Cells Divide Instead of Just Growing Bigger and Bigger?
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The cell's _____ would no longer be able to serve the increasing needs of the growing cell.
The cell has more trouble moving enough _________ and ________ across the cell membrane.
o Larger cells have a smaller ratio of surface area to volume.
Prokaryotic vs. Eukaryotic
Prokaryotic Cell Division: Binary Fission
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Eukaryotic Cell Division: ____ ______
Eukaryotic vs. Prokaryotic DNA
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Prokaryotic DNA – located in the _______________
o Lack nucleus and many eukaryotic organelles
o Have a single circular DNA molecule (usually referred to as
cell's chromosome)
Eukaryotic DNA- located in the ______________in form of various chromosomes
the
Deoxyribonucleic Acid (DNA)
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Definition:
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Responsible for determining all organism’s traits (sequence of bases):
o Ex’s ________________________________________
The Components of DNA
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DNA is a long molecule made up of repeating individual units
called ___________________________
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Nucleotides are made up of three parts:
1.
2.
3.
**Nucleotides Put Together = DNA
DNA contains four nitrogenous bases:
1.
2.
3.
4.
Which bases pair with each
other??
[
]=[
]
[
]=[
]
____________________discovered that there were always equal amounts of A & T. And equal amounts of C & G in cells.
The base pairs are held together by _______________ bonds. (No matter what organism it is!!!!)
Purines and Pyrimidines
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Purines have _________ rings in their structures. ( ___________& ________________ belong to this group)
Pyrimidines have ______ ring in their structure.(___________&____________belong to this group)
Structure of DNA
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___________________&_____________________ - Form the backbone or sides of the ladder.
___________________________- Form the “rungs” of the ladder or middle of the molecule.
Shape of DNA: DNA looks like a “twisted ladder” called a _________________________.
Discovering DNA
1. _______________________________ - Used X-ray diffraction; Showed the X-shaped pattern of DNA (helix shape)
2. ____________________ and _____________________ – Two scientists that discovered the double helix shape in 1953
You Try It!
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What is the complimentary DNA strand if the original DNA strand is AGTCTA? ______________________
Chromosomes
_________________________ - Very long, continuous single piece of DNA, contains many genes
_________________ - Sequence of DNA that codes for a protein and thus determines a trait
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In eukaryotic cells, the genetic information that is passed on from one generation of cells to the next is carried by
chromosomes.
The cells of every organism have _________________________________________
o The cells of fruit flies have 8 chromosomes.
o Human cells have __________ chromosomes.
o Carrot cells have 18 chromosomes.
Chromosomes are not visible in most cells except during
_______________________.
Well before cell division, each chromosome is ___________________
(During the S Phase of Interphase).
DNA molecules are surprisingly long: 4, 639, 221 base pairs in E. coli
At the beginning of cell division, however, the chromosomes
condense into compact, visible structures; they are folded and
tightly packed to fit within the cell.
Each chromosome consists of two identical “sister”
_______________________.
o When the cell divides, the “sister” chromatids separate from
each other.
o One chromatid goes to each of the two new cells.
Each pair of chromatids is attached at an area called the
________________________.
If a meerkat’s parent skin cell contained 34 chromosomes; after cell
division how many chromosomes would each of the meerkat’s
daughter skin cells contain? _________________________
S-Phase: DNA Replication
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Before a cell divides, it duplicates its DNA via a process called
___________________________
Occurs during ______________________ of cell division
Ensures that each resulting cell will have a complete
_______________ set of DNA molecules
Result: Two identical DNA molecules (each DNA molecule has one
original strand and one new strand)
How DNA Replication Occurs
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Step 1:
o Helicase, an enzyme, ______________________________________
o Hydrogen bonds between ____________________ are broken
o Result = 2 separated strands of DNA
Step 2: A replication fork is formed.
Step 3: Free floating nucleotides pair up with complimentary bases
o Each strand of DNA serves as a template, or model, for the new strand
o DNA Polymerase –
Eukaryotic Cell Cycle
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Cell Cycle - Series of events that cells go through as they grow and replicate.
o Interphase - Period of the cell cycle between cell divisions (consists of _________________ phases)
o M Phase –
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(division of the cell nucleus)
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(division of the cytoplasm)
o There are 3 “__________________________” that allow the cells to continue moving through the cell cycle.
Regulating the Cell Cycle
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Not all cells move through the cell cycle at the same
rate.
Cell growth and cell division are controlled.
______________________ are proteins that regulate the
timing of the cell cycle in ___________________.
If cells are placed in a petri dish containing nutrient
broth (provides food for the cells):
o Cells will grow until they form a thin layer
covering the bottom of the dish.
o Then, the cells stop growing, when they come
into ______________________________ with other cells.
If cells are removed from the center of the dish:
o The cells bordering the open space will begin dividing until they have filled the empty space.
This occurs in an injury as well:
o
o
If a cut in the skin or a break in a bone occurs, cells at the edges of the injury are stimulated to divide rapidly.
When the healing process nears completion, the rate of cell division slows down.
Cancer
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Cancer –
o Cancer cell divide ____________________________________ and form masses of cells (tumors)
o Cancer cells may spread throughout the body:
o Disrupts normal activities and causes serious medical problems or even death
o There are many reasons that cells can divide and grow out of control:
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Exposure to environmental causes:
Nutritional deficiencies; genetic causes; some infections
Cell Cycle (2 phase)- Interphase
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G1 Phase –
o G1 Checkpoint
S Phase –
G2 Phase –
o G2 Checkpoint
Cell Cycle – M Phase (cell division)
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Cell Division –
M Phase –Mitosis (division of the cell nucleus)
Cytokinesis (division of the cytoplasm)
o Before cell division occurs, the cell replicates, or copies, all
of its DNA.
o Each daughter cell gets one complete set of genetic
information.
Asexual Reproduction
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Reproduction by Mitosis is classified as asexual, since the cells
produced by mitosis are:
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Asexual Reproduction - Reproduction without the fusion of gametes; not necessary to have ______ parents
o Examples include:
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Four Phases of Mitosis
1. _________________________(chromosomes visible/centrioles; nuclear envelope disappears)
2. _________________________ (microtubles line the chromosomes up in middle of cell )
3. __________________________ (sister chromatids separate to opposite ends of cell)
4. __________________________ (chromosomes condense back to chromatin and nuclear envelope reappears)
(Four phases are followed by _____________________________)
Cytokinesis - Usually occurs at the same time as ________________.
It is the division of the _____________
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Animal Cells: _________ __________
Plant Cells: _________ __________