Preap/GT Cell Cycle Notes 2015

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. Eukaryotic Prokaryotic Cell Division: Binary Fission



Eukaryotic Cell Division: ______

Eukaryotic vs. Prokaryotic DNA  Prokaryotic DNA – located in the ______o Lack nucleus and many eukaryotic organelles o 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: 1.1.1. 1.1.2. 1.1.3. **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  ______&______- 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 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  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 death

o 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

 G1 Phase –

o G1 Checkpoint

 S Phase –

 G2 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 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 ______

 Animal Cells: ______

 Plant Cells: ______