PreAP/GT Cell Cycle Notes 2015

Why Do Cells Divide Instead of Just Growing Bigger and Bigger? 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. EukaryoticProkaryotic Cell Division: Binary Fission

Eukaryotic Cell Division: ____ ______

Eukaryotic vs. Prokaryotic DNA Prokaryotic DNA – located in the _______________

o Lack nucleus and many eukaryotic organelleso Have a single circular DNA molecule (usually

referred to as the cell's chromosome) Eukaryotic DNA- located in the ______________in form of various chromosomes

Deoxyribonucleic Acid (DNA) Definition:

Responsible for determining all organism’s traits (sequence of bases): o Ex’s ________________________________________

The Components of DNA DNA is a long molecule made up of repeating individual units

called ___________________________ Nucleotides are made up of three parts:

1.2.3.

**Nucleotides Put Together = DNA

DNA contains four nitrogenous bases:1.2.3.4.

____________________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

Purines have _________ rings in their structures. ( ___________& ________________ belong to this group)

Pyrimidines have ______ ring in their structure.(___________&____________belong to this group)

Structure of DNA

Which bases pair with each other??

[ ] = [ ]

[ ] = [ ]

___________________ &_____________________ - 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!

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

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

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 Step 1:

o Helicase, an enzyme, ______________________________________o Hydrogen bonds between ____________________ are brokeno 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 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 – (division of the cell nucleus) (division of the cytoplasm)

o There are 3 “__________________________” that allow the cells to continue moving through the cell cycle.

Regulating the Cell Cycle 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 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.

o When the healing process nears completion, the rate of cell division slows down.

Cancer 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 deatho There are many reasons that cells can divide and grow out of control:

Exposure to environmental causes: Nutritional deficiencies; genetic causes; some infections

Cell Cycle (2 phase)- Interphase G 1 Phase –

o G1 Checkpoint S Phase – G 2 Phase –

o G2 Checkpoint

Cell Cycle – M Phase (cell division)

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 Reproduction by Mitosis is classified as asexual, since the cells produced by mitosis are:

Asexual Reproduction - Reproduction without the fusion of gametes; not necessary to have ______ parents

o Examples include:

Four Phases of Mitosis1. _________________________(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 _____________

Animal Cells: _________ __________ Plant Cells: _________ __________