Cell Cycle Flashcards
What are the reasons for Cell Division?
- Reproduction: Cells undergo reproduction to pass on genetic information to new cells
- Growth: increase in the number of cells to grow larger
- Repair: cells also grow and divide to replace cells lost because of normal wear and tear or injury. Some cells, such as epithelial (cancer) cells, reproduce quickly. Other cells, like nerve cells, grow slowly.
How does cellular cycling affected by the environment a cell is in?
Cells die when they get damaged, so new cells need to replace them; some cells are replaced and repaired more often then others- the frequency of the cellular growth and reproduction is dependent on the environment the cell is in. In a harsh environment, there will be a lot of death and the need to replace the cells more often.
Give an example of when cells would need to repair or reproduce more often than another.
Skin cells are more exposed to the outside environment, stomach cells are constantly exposed to stomach acid that corrodes the tissue lining; on the other hand, brain cells are not often replaced.
What is G0 Phase
The cell performs all of its normal functions but is not prepared to divide.
Some cells often decide and either are in G0 for a short amount or skip G0. The cells do not divide very often and are in the G0 phase for many years.
When the cell receives the signal to divide it moves into the G1 phase of the cell cycle.
What is the G1 phase?
The cell prepares to undergo cell division
The cell still performs all of its normal functions but starts to get bigger.
The cell begins to make a copy of the cell parts (organelles) it also begins to make more promotion to get ready to divide.
The time for this phase varies from about 8 hrs to several days, weeks or months.
What is the G2 phase?
The cell makes more proteins in preparation for cell division
This phase lasts about 2-5 hours
What is the Synthesis phase?
The cell copies its DNA (DNA synthesis) to make 2 sets of chromosomes - one set for each new cell.
This phase lasts about 6-8 hours.
The three phases of the Cell cycle are (In order)
interphase, mitosis, and cytokinesis
What happens if a cell is unable to pass a checkpoint?
Apoptosis (cell death) or the cell remains in the state for the rest of its lifespan.
- If the cell doesn’t pass a checkpoint it enters G0 to ensure that conditions are correct for it to proceed again
What is a checkpoint?
A checkpoint is a stage in the eukaryotic cell cycle at which the cell examines internal and external cues and “decides” whether or not to move forward with division.
What are each checkpoints a cell needs to pass?
There are a number of checkpoints, but the three most important ones are:
The G1 checkpoint, at the G1/S transition.
The G2 checkpoint, at the G2/M transition.
The spindle checkpoint, at the transition from metaphase to anaphase.
How can the cell continue past the G1 checkpoint?
The cell continues past this point if the:
- Cell size is large enough
- There are enough nutrients for the cell
- Social signals are present (cells communicate with one another to operate in multicellular organisms)
- DNA is not damaged
How can the cell continue past the G2 checkpoint?
The cell passes this checkpoint if:
- Chromosomes have been duplicated correctly
- DNA is not damaged
How can the cell continue past the Metaphase checkpoint?
All chromosomes are checked to see if they are attached to the spindle fibers
What are telomeres?
A region of repetitive nucleotide sequences at each end of a chromosome, which protects the end of the chromosome from deterioration from fusion with neighbouring chromosomes.
What is Mitosis?
a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus
What is meiosis?
Meiosis: Passing on of genetic information from the parent to offspring cells, reason for the cell cycle.
What are chromosomes?
a long piece of coiled DNA and proteins, only visible when the cell is dividing.
Karyotype Definition?
an organized display of chromosomes, the 23rd pair are sex chromosomes, females have XX and males have XY
Definition Chromatin?
When the cell is not dividing, the DNA and proteins that make up the chromosomes are spread throughout the cell
What are Sister Chromatids?
two identical copies of chromosomes
What are Centromeres?
part of a chromosome that links a pair of sister chromatids
What are Centrioles?
paired barrel-shaped organelles located in the cytoplasm of animal cells
What are Nuclear Envelope?
membrane barrier that separates the nucleus from the cytoplasm
What are Spindle Fibres?
made up of microtubules, involved in moving and segregating the chromosomes during mitosis
What are the Stages of Mitosis?
prophase, metaphase, anaphase and telophase
What is the Prophase?
The first stage of mitosis.
The chromosomes duplicate to form two long, thin strands called chromatids. And the chromatids condense and thicken to form distinct bodies.
- nuclear membrane begins to disappear
- centrioles move to poles
- Spindle fibres start to form
What is the Metaphase?
During metaphase, the nucleus dissolves and the cell’s chromosomes condense and move together, aligning in the center of the dividing cell. Sister chromatids line up at the metaphase plate (the equator of the cell)
What is the Anaphase?
Spindle fibres retract and break sister chromatids (now called chromosomes) are pulled apart into chromosomes that move to either side of the cell (opposite poles).
What is the Telophase?
The process that separates the duplicated genetic material carried in the nucleus of a parent cell into two identical daughter cells.
- Nuclear envelopes reform around chromosomes (Two new nuclei form, one for each set of chromosomes (pair chromosomes have been seperates and pulled to opposite poles of the cell))
- Chromosomes stretch out to chromatin
What is Cytokinesis in Animal Cells?
Cell membrane pinches until the original parent cell is divided into two equal daughter cells
What is Cytokinesis in Plants?
A cell plate forms between the two nuclei which will generate a new cell wall dividing the original parent cell into two equal daughter cells
- The Golgi body produces small vesicles which carry material needed to create the new cell wall
- Cell plate: vesicles that line up between the two nuclei
The cell plate grows outward and joins the old cell wall.
