Chapter 5 The Cell Cycle
Terms in this set (97)
The regular pattern of growth, DNA Duplication, and cell division that occurs in Eukaryotic cells
(The lifetime of the cell)
How do stages of the cell cycle get their names?
From early studies of cell division
Ex.= Gap 1 because the cell was dividing so they thought nothing was happening, it was just a gap
Phases of Interphase
Gap 1 (G1)
Gap 2 (G2)
Phases of Mitosis
Where does a cell spend most of its time?
In the G1 stage, although the length of this stage varies by cell type
Cells just doing their job,
Cells carry out their normal functions and undergo critical growth and preparation for cell division
What is taking place in the cell during G1?
The cell is carrying out its normal functions, the cell increases in size, and the organelles increase in number.
What must happen to the cell before it can go to the synthesis stage?
It must pass a critical checkpoint
What conditions must be met in order for the cell to pass the checkpoint from G1 to S?
The cell needs: enough nutrition, adequate size, relatively undamaged DNA, and specific signals from other cells telling the cell whether more cell division is needed
Means the combining of parts to make a whole
What is taking place during the S stage?
The cells makes a copy of its nuclear DNA, creating two complete sets of DNA
Cells continue out their normal functions and additional growth occurs
What must happen to the cell before it can go to divide?
The cell must pass a critical checkpoint before going to mitosis and division
What conditions must be met by the cell in order to pass from G2 to Mitosis and cell division?
The cell must have adequate size and undamaged DNA
The division of the cell nucleus and its contents
The nuclear membrane dissolves, the duplicated DNA condenses around proteins and separates and two nuclei from
The process that divides the cell cytoplasm
What characterizes cells that are in the G0 Phase?
Those cells are unlikely to divide or divide rarely but continue oout their normal functions
Examples of cells that are in the G0 Phase?
Neurons (Nerve cells) and Lymphocytes (White blood cells)
What must happen for a cell to maintain a suitable cell size?
Growth and Division must be coordinated
One long continuous strand of DNA
What is the DNA like during interphase and mitosis?
During Interphase the DNA is loosely organized so it is accessible for transcription
During Mitosis the DNA is tightly condensed to keep it organized so that each new cell gets a complete set of chromosomes
What makes DNA able to coil into its highly condensed form?
The loose form of DNA and Histones
Formed from DNA wrapping around Histones at regular intervals (like beads on a string)
What happens to the chromatin as the cell progresses through mitosis?
It's coiling more tightly until it forms a thick rod
Why does the chromosome have a X appearance?
Because DNA was replicated during the S phase
Each side of the X (2 copies of DNA)
Two identical chromatids are referred to as ____________
The regions that holds up the sister chromatids
Structures that form at the end of DNA molecule that prevent the end of chromosomes from attaching to each other and also prevent the loss of genes during replication
What do mitosis and cytokinesis produce?
Two genetically identical daughter cells
Prepares a cell for division by providing time for growth, replication of the DNA, and duplication of organelles
Divides a cells nucleus into two genetically identical nuclei in all cells except eggs and sperm
The division of the cytoplasm which begins near the end of mitosis
Phases of mitosis
Chromatin condenses into chromosomes
Nuclear envelope breaks down
Centrosomes and centrioles move toward opposite ends of the cell
Microtubules called spindle fibers grow from the centrioles and radiate towards the center of the cell
Spindle fibers attach to a structur on the centromere and pull the chromosomes to the middle of the cell
Sister chromatids separate and are pulled to opposite ends of the cell by the spindle fibers
Complete set of chromosomes is at the pole of each cell
Nuclear membrane starts to form
Spindle falls apart
Nucleolus reforms now there is 2 nuclei
Chromosomes uncoil and go back to the chromatin form
When does cytokinesis begin?
Begins in telophase but it is not apart of mitosis
Cytokinesis is different in what cells?
Plant and animal cells
Cytokinesis in animal cells
The cell membrane forms a cleavage furrow that is pulled inward by Microfilaments until the cytoplasm has divided into two cells
Cytokinesis in plants cells
A partition (formed by the Golgi) called a cell plate forms between the two nuclei forming the new cell membrane
The newly formed cell wall formed from cellulose
Cell division is critical for ____________
Both unicellular and multicellular organisms
Why do unicellular organisms use cell division ?
To reproduce (asexual reproduction)
Why do multi cellular organisms use cellular division?
Growth development and repair
What regulates the cell cycle in Eukaryotic Cells?
External and Internal factors
Why is cell regulation necessary?
For healthy growth of the cell
What does cell regulation do?
Makes sure DNA is replicated properly
Chemical Signals start and stop the cell cycle
Cells communicate with each other so they don't become overcrowded-- contact inhibition
Around how many times does a normal cell divide?
Around 50 times
A cells natural death
Programmed cell death
When does Apoptosis occur?
When internal or external signals activate genes that help produce self destructive enzymes
What happens in Apoptosis?
Nucleus of the dying cell shrinks and breaks apart
Cells in the immune system gobble up the apoptic cell and recycle its chemical parts
Come form outside the cell
Includes messages from nearby cells and from distant parts of the organisms body
Physical and Chemical signals
Example of a physical Signal
When the healthy/ normal cells run into each other they stop dividing
A broad group of proteins that stimulate cell division
They bind to receptors that activate specific genes to trigger cell growth
Enzyme controlled stop and go signals
An enzyme that activates/inactivates another molecule by adding a phosphate
Activate the Kinases that help control the cell cycle
Cyclin Dependent Kinases (Cdks)
Control different activate at different stages of the cell cycle
Help a cell advance to different stages of the cell cycle
(Controlled by Protein Complexes) They monitor the cell cycle
What are the 3 checkpoints?
Divide yes or no?
Is cell large enough?
Is food available?
is DNA all there and intact?
What happens to the cell if it does not meet the criteria to pass a checkpoint?
The cell will not move on
Has DNA successfully replicated?
Are all of the chromosomes attatched to the Spinde?
A disease of the cell cycle, the cells have genes that have been altered or mutated
When does Cancer occur?
When the cells lose the normal controls that determine when and how often they divide
Why are the mutated genes in cancer cells bad?
Because many of the genes encode proteins that control the cell division cycle of a normal cell
Genes in normal cells that stimulate cell division, turned off most of the time, "Go" Genes
What happens to Oncogenes in cancer cells?
In Cancer cells mutations turn these genes on consistently causing cell division out of control
in normal cells they encode proteins to inhibit cell division "Stop" genes, turned on most of the time
What happens to the Tumor-Suppressor Genes in cancer cells?
In cancer cells these genes are turned off cell division occurs constantly
Breast Cancer Genes
BRCA1 and BRCA2
What happens to out of control cancer cells?
Uncontrolled mass of cells that invades and disrupts surrounding tissue- not contact inhibition
The cancer cells typically remain clustered together, the tumor is probably harmless and can be cured by removing it
Cancer cells can break away (metastize)from the tumor
Cancer cells lose their adhesion to other cells break away and spread throughout the body
When do immortal cells die?
They die when the entire organism dies
Famous example of immortal cells?
HeLa Cells from Henrietta Lacks--- have been growing and dividing since 1951
Causes of Cancer
1. Spontaneous Mutation
2. Cigarette Smoke= Lung Cancer
3. X-Rays and UV Radiation
5. Some viruses are linked to certain cancers
What are some viruses that lead to Cancers?
HPV---> Cervical Cancer
Hepatitus B------> Liver Cancer
2 Standard Cancer Treatments
Kills cancer cells and shrinks tumors
Damages a cells DNA so much that it can't be divided
Uses drugs, often in combination, to kill actively dividing cells
Travel throughout the whole body
Unique type of body cells that has the ability to
1. Divide and renew themselves for long periods of time
2. Remain undifferentiated in form
3. Develop into a variety of cell types-- meaning they are generic cells not specialized in any way yet
3 Types of Stem Cells
1. Adult Step Cells
2. Embryonic Stem Cells
3. iPS Cells (induced pluripotent stem)
Adult Stem Cells
Partially undifferentiated cells located among the specialized cells of many organisms
Can only formto closely related cells= multipotent
Example: stem cells from bone marrow can give rise to all types of blood cells
Multipotent vs. Pluripotent
Multipotent- the cells must be closely related, it is a limited range of potential
Pluripotent- a lot of potential
Embryonic Stem Cells
After fertilization mitosis occurs, approx. 10 days after fertilization there is a mass of 100-150 cells
These cells have not yet begun to specialize and can become any type of cell in the human body
These cells are what would become a baby!!!
Somatic cells altered to become pluripotent stem cells
Meaning- skin cells were taken and turned into stem cells so that the newly made stem cells could be used to make any kind of cell
Body cells; any cell in the body except egg/sperm cells
Takes somatic cells backwards to a pluripotent state
How did the creation of Somatic Cells come about?
Dr. Yamanaka did the experiment and tests in 2007 and they were confirmed by 4 separate labs