Mitosis and the Cell Cycle Flashcards
What is the process by which new cells are formed?
Cell Reproduction
What is the difference between cell reproduction and the reproduction of a multicellular organism?
The number of “parents” involved.
When body cells and most single-celled organisms reproduce, there is only one parent:______________________________________
One cell divides to produce two new cells, which are called daughter cells.
The two daughter cells are _______ to each other and to their parent cell, at least in the genes they contain.
Identical
In sexual reproduction, two parents mate and the offspring receive ____ of their genes from each parent (one chromosome from each pair of chromosomes).
Half
True or False: Although offspring share genetic material and may look alike, they are not exactly the same.
True
Cell Division Definition
The process by which a parent cell divides into two daughter cells.
For single-celled organisms, _____ ____ is the main process by which individuals reproduce, and the population gets larger.
Cell Division
What is the process by which a fertilized egg (a single cell) becomes, eventually, an adult with millions of cells?
Cell Division
True or False: In multicellular organisms, cell division is also the process by which you replace lost or damaged cells.
True
True or False: The contents of a cell, particularly its nucleus, are complicated.
True
Each cell has to take an ________ approach to cell division-it cannot just break in two.
Organized
The nucleus contains the _______, which is so important that the nucleus has its own multi-step division process, called _________.
DNA; Mitosis
Mitosis Definition
The process by which the duplicated contents of the cell’s nucleus divide into two equal parts.
What is the different process that the cytoplasm divides by?
Cytokinesis
Cytokinesis Definition
Following mitosis, the separation of the two nuclei and cell contents into two daughter cells.
DNA is divided into segments called _______, each of which provides the instructions for making a different protein.
Genes
True or False: Your body needs all of these proteins at one time or another-each plays a role in making up the structure of, or ensuring the proper function of, your body’s many parts.
True
Thus, every cells needs to have all the _______ required to make these proteins.
Genes
Although not every cell will end up making every protein, each starts out with the ______ to do so.
Potential
Therefore, the parent cell cannot just divide its _____ equally between its two daughter cells when it divides.
Chromosomes
True or False: If this happened, each daughter cell would only have half the number of chromosomes its parent had and would be missing vital genes.
True
In the case of human cells, each daughter cell produced through cell division needs a copy of all ______ chromosomes from its parent cell.
46
A parent cell therefore makes a copy of every chromosome before it _______.
Divides
It can then give one copy to each of the __________ _____.
Daughter Cells
What is this copying process called?
DNA Replication
DNA Replication Definition
The process by which DNA is copied, creating sister chromatids joined at the centromere.
Chromosomes are normally more like very long, loose threads until when?
Until the cell gets ready to divide.
What does each “thread” consist of?
A tightly twisted strand of DNA.
Just before the cell gets ready to divide, what happens to the chromosomes?
They take on a thick, bulging look.
True or False: DNA Replication is very precise.
True
When copying errors occur, they are usually _____ and _____ by special “proofreading” and repair proteins.
Detected and fixed
At roughly the same time the DNA is replicated, what is the organelle called that also doubles, so that the cell has two copies?
The Centrosome
The centrosomes help to organize the ______ that make up the ______, and play an important role in cell division.
Tubules; Cytoskeleton
What are the six stages of Mitosis? (In order)
-Interphase
-Prophase
-Metaphase
-Anaphase
-Telophase
-Cytokinesis
Prophase Definition
The phase of mitosis in which sister chromatids condense and the chromosomes become visible.
What happens during Prophase? (5 Points)
-Nuclear membrane begins to disappear
-Duplicated DNA condenses into chromosomes that are visible with light microscope.
-Each chromosome has identical DNA.
-Centrosomes: Organelles in cytoplasm head to opposite ends of the cell.
-Fibres from centrosomes start extending out towards the centre of each duplicated DNA (Centromeres on each Chromosome)
Metaphase Definition
The phase of mitosis in which the chromosomes are aligned across the centre of the cell.
What happens during Metaphase? (2 Points)
-Fibres of centrosomes attach to centromeres, lining up chromosomes in the middle of the cell.
-This is the longest phase of mitosis
Anaphase Definition
The phase of mitosis in which the centromere splits apart and the chromatids are pulled to opposite sides of the cell by the spindle fibres.
What happens during Anaphase? (3 Points)
-The two copies of DNA split into 2 chromosomes.
-New chromosomes are pulled to opposite sides of the cell by spindle fibres of the centrosome
-At this point the cell has 92 chromosomes
Telophase Definition
The phase of mitosis in which two daughter nuclei are formed.
What happens during Telophase? (5 Points)
-Fibres start the disappear
-Membranes begin to form around the two nuclei
-46 identical chromosomes are in each nucleus
-Chromosomes begin to uncoil
-The rest of the cell prepares to divide.
What happens during Cytokinesis? (2 Points)
-Elongated cells begin to pinch apart at the centre
-Cytoplasm divides into two parts
True or False: The division of the rest of the cell-the cytosol and organelles-usually begins before telophase is complete.
True
The cell division process must be carefully controlled for what to function properly?
Your body
Some types of cells must be “encouraged” ______ ____ and other must be “encouraged” __ _______ _____ _____ _____.
To divide; To remain as they are.
This is the job of molecules, most proteins, that ___ _____ ___ ___, ______ _____ ____ ______ _______ _____ ____.
Carry signals among cells, sharing information about various cells’ abundance and health.
True or False: These molecules control the cell cycle.
True
What does the Cell Cycle-the life cycle of a cell-consist of?
Two main phases: Cell Division and Interphase
Cell Cycle Definition
A continuous sequence of cell growth and division, including the stages of interphase, mitosis and cytokinesis.
Interphase Definition
Periods of growth in the life of a cell; consists of two growth stages and a stage of DNA replication.
What happens first in the cell cycle? (Additional 2 Points)
Cell Division:
-First, the cell’s nucleus divides into two parts during mitosis.
-Then, the two nuclei and cell contents divide into two daughter cells during cytokinesis.
What happens next in the cell cycle after cell division? (With 4 additional points)
Interphase:
-Cells do whatever activities they are designed to do, such as producing specific proteins.
-It also does the things that all cells do, such as taking in oxygen and glucose, releasing energy from glucose (cellular respiration) and removing wastes.
-In addition, DNA replicates in preparation for cell division.
-Before and after the DNA replicates are two periods during which the cell produces more organelles and grows larger.
What is vital to normal growth and development?
Controlling the timing and rate of cell division in different parts of a plant or animal.
True or False: Too few or too many cells in any one body part can lead to serious problems.
True
True or False: There are three main points at which the cell “checks” its growth.
True
Cell Cycle Checkpoint Definition
A point in the life of a cell when proteins determine whether cell division should or should not occur.
What acts like stop signs at each checkpoint?
Specialized Proteins
Unless they receive ______ ______ ____, they will not let the cell cycle proceed.
Specific go-ahead signals
In general, cell division will not occur if:
-There are not enough nutrients to support cell growth
-The DNA has not replicated
-The DNA is damaged
For many cells, what is the most important checkpoint?
The first one after mitosis.
True or False: Many cells leave the cycle after this checkpoint, often just because more cells of that type are not required.
True
The body does not need that cell to divide, so it does not receive a _________ signal.
Go-Ahead
Cells that leave the cycle enter what stage?
A non-dividing stage.
True or False: Most cells in the human body-all muscle and nerve cells, for example, are in this stage.
True.
What does the first checkpoint during the mitosis phase check for?
-If the chromosomes have attached themselves to spindle fibres in metaphase.
-If the chromosomes have moved to the poles in anaphase.
What does the second checkpoint during the growth and preparation phase check for?
-If the cell has enough nutrients to support its growth.
-If the DNA is damaged.
What does the third checkpoint during the continued growth and preparation phase check for?
-If the DNA has replicated.
-If the DNA is damaged.
Why does Mitosis occur?
- Growth
- Maintenance
- Repair (Cuts)
What happens during Interphase? (3 Points)
-This is the stage that the cell spends the most of its life in.
-A time where growth and normal cell functions are occurring.
-Prepare for Division:
-DNA replication in the nucleus
-Copies organelles.
What happens during Cytokinesis in Animal Cells? (3 Points)
-A ring of specialized proteins around the middle of the cell starts to contract.
-Like pulling the drawstrings on a bag, this contraction pinches the cell membrane until the parent cell is divided into two parts.
-Each daughter cell has a complete set of chromosomes in a nucleus and its own share of cytosol and organelles.
What happens during Cytokinesis in Plant Cells? (Include Cell Plate Definition) (9 Points)
-The same process as in animal cells.
-However, in plant cells, rigid cell wall makes it necessary for the process to be different.
-The Golgi body starts to produce small vesicles.
-Each of these sacs carries the materials needed to form a new cell wall.
-The vesicles line up between the two new nuclei, forming a cell plate.
-Cell Plate: A structure that helps to form the cell wall in the process of plant cell cytokinesis.
-The cell plate grows outward and joins the old cell wall.
-New cell walls are secreted on each side of the cell plate, dividing the cytoplasm into two.
-Then new cell membranes form inside the cell walls, and the division is complete.
Explain Cell Death (3 points)
-Some cells do not leave the cell cycle to become specialized-they leave the cell cycle because it is time for them to die.
-In some cases, this is because they have been damaged beyond repair, perhaps by physical forces or by exposure to toxic chemicals.
-The contents of the cells leak out, often irritating surrounding cells, causing swelling and redness in the body part.
Explain Cell Suicide (6 points)
-Other cells carry out a kind of suicide.
-In this case, a cell breaks down in an organized way.
-Its contents are packaged and distributed so that other cells can use them.
-Scientists have learned that this type of death is pre-programmed into cells, determined by what are often called “suicide genes.”
-These genes code for proteins who job is to kill cells in specific situations.
-Cells may also ensure their own death when their survival would be a threat to the organism.
Complete Mitosis Worksheet
Depending on Comfort Level
What are the Stages of Interphase? Also, what is produced as the cell grows because of what?
-G1 phase: cell growth and presentation
-S phase: DNA replication
-G2 phase: cell growth and preparation
-As cell grows more organelles are produced in preparation for division
