Chapter 8.4 Flashcards
Cell Cycle
The series of events that take place in a cell leading to its division
Interphase
Active preparation for cell division. In which most eukaryotic cells spend their time.
What does interphase include
G1 PHASE : Normal cell function and cell
growth
S PHASE : DNA Replication
G2: PHASE: Additional growth and preparation for division
After Interphase
The cell divides in Mitosis
In what phase does replication occur
Interphase
cytokinesis
The process in which a eukaryotic sperates into two identical daughter cells
What happens to the newly formed daughter cells
The enter the cell cycle at interphase
GAP 1 PHASE
Normal Cell function and growth
The cell grows, carries out basic functions and produces molecules needed to build new organelles and other components it will require if it divides
A cell in G1 is sensitive to what
To external signals that tell it whether it should
- Divide
- Stop to repair damaged DNA
- Die
- Enter a non dividing stage G0
G0 PHASE
a cell continues to function, but it does not replicate its DNA or divide
. At any given time most cells are in this stage
. It is reversible
What cells are permanently in G0
Muscle Cells
Nerve Cells
which explains why the brain does not grow after it reaches its adult size and brain damage is often irreparable
S (synthesis) phase what 2 things that occur
1.Dna Replication
enzymes replicate the cell’s genetic material and repair damaged DNA.
- Duplication of Centrosomes
Why did biologist mistakenly believed that interphase was an inactive time
Because the Chromatin is unwound and therefore barely visible.
The product of S Phase ( DNA Replication) is
At the end of replication are 2 sister chromatids ( that are not visible under the microscope as yet)
What are CENTROSOMES
Strucures that organize the proteins that will move the chromosomes during mitosis.
What do centrosomes consist of
a cloud of proteins enclosing a pair of barrel shapes CENTRIOLES
What occurs in Gap Phase 2
- the cell continues to grow
- prepares to divide
. Produces the proteins that will coordinate the movement of the chromosomes during mitosis
. Dna condenses more tightly ( signals that mitosis will begin and interphase is about to end)
Explain the events of the cell cycle
Interphase is the period in which the cell prepares for division
- G1 ( Zygote- first cell) Cells increase in size in Gap 1. The G1 checkpoint control mechanism ensures that everything is ready for DNA synthesis.
- G0 A resting phase where the cell has left the cycle and has stopped dividing.
- S DNA replication occurs during this phase.
- G2 During the gap between DNA synthesis and mitosis, the cell will continue to grow. The G2 checkpoint control mechanism ensures that everything is ready to enter the M (mitosis) phase and divide.
- M Cell growth stops at this stage and cellular energy is focused on the orderly division into two daughter cells. A checkpoint in the middle of mitosis (Metaphase Checkpoint) ensures that the cell is ready to complete cell division.
Explain the two packaging stages of DNA and when they occur
CHROMATIN : DNA is loosely packed in the nucleus and available for DNA replication and protein synthesis. ( G1, beginning of S phase)
2 CHROMOSOME: Tightly wounded dna.
Begins shortly after replication. In (G2), it begins to condense in preparation for mitosis cell division.
A Cellthat has completed interphase has how much DNA than a cell at the the beginning.
double: from dna replication in the S phase
overall what happens in Mitosis to the cell
Separates the genetic material that was replicated in the s phase into 2 daunter cells.
MITOTIC SPINDLE
An array of proteins that ensures that the chromosomes are distributed evenly in two sets that are then pulled to the opposite poles of the cell.
. It consists of microtubles that form the the fibers that grow outward front the centrosome
The mitotic Spindle aligns Chromosomes how
The mitotic spindle consists of microtubles that form the fibers that grow outward from two centrosomes ( proteins and centrioles). The spindle fibers push and pull to align the chromosomes.
the 6 Phases of Mitosis
Prophase Prometaphase Metaphase Anaphase Telophase Cytokinesis
PROPHASE
.”pro” before
. The first stage of cell division ( mitosis)
1.Dna coils up very tightly (chromosome),shortening and thickening the CHROMOSOMES(The sister chromatids recently replicated becomes visible)
. They are arranged randomly in the nucleus
2. The CENTROSOMES move to the poles of the the cell, as they do this
- MITOTIC SPINDLE begins to form
- NUCLEOLUS disappears
PROMETAPHASE
. “before metaphase”
. Occurs immediately after the formation of the spindle.
1. Nuclear envelope (and associated endoplasmic reticulum) breaks up into small pieces , enabling the spindle fibers to reach the chromosomes.
1B. The chromosomes are loose within the cell
2. Meanwhile, proteins called kinetochores begin to assemble on each centromere; these proteins attach the chromosomes to the spindle fibre.
- The spindle fibres attach to the kinetochores on chromosomes
KINETOCHORES ( kineto- + chora, space)
Proteins that attach the chromosomes at their centromere to the spindle fiber.
. They are formed during pro metaphase, they begin to assemble at each CENTROMERE
Explain the relationship of MITOTIC SPINDLES,
MICROTUBULES
AND SPINDLE FIBRES
- MICROTUBULES: are fibres that grow outward from 2 centrosomes
- SPINDLE FIBRES: are the microtubules that attaches to the kinetochores of centromeres
- MITOTIC SPINDLE: collectively refers to all the microtubules
Metaphase
. meta ( means middle)
Chromosomes are aligned in the center/ middle / equator of the cell by the mitotic spindle attached kinetochores
Why are Chromosomes are aligned in the center/ middle / equator of the cell by the mitotic spindle.
This alignment ensures that each cell will contain one sister chromatid from each duplicated chromosome.
ANAPHASE
- CENTROMERES split as MITOTIC SPINDLE PULLS sister CHROMATIDS apart.
- Some Spindle fibres shorten reeling in sister chromatids to opposite poles of the cell near the centrosomes.
- Others lengthen in a way that moves the poles further apart stretching the dividing cell.
TELOPHASE (telos, end)
. The final stage of mitosis
1. Nuclear envelope and nucleolus forms at each pole. ( opposite of pro metaphase)
The cell has two nuclei
2. Chromosomes decondenses ( opposite of prophase)
3.The mototic spindle disassembles
The division of the genetic material is complete.
CYTOKINESIS
organelles and macromolecules are distributed into two forming daughter cells, which then physically separate.
CLEAVAGE FURROW
In an animal cell, is the first sign of cytokinesis.
a slight indentation around the middle of the cell
What causes the cleavage furrow
A contractile ring of actin and myosin proteins that form beneath the cell membrane
CELL PLATE
The first sign of cytokinesis in plants.
( a dividing plant cell must construct a new wall that separates the two daughter cells
How is the CELL PLATE form
vesicles from the Golgi apparatus travel along microtubules, delivering structural materials such as cellulose fibers, other polysaccharides and proteins to the midline of the dividing cell.
Although cytokinesis follows mitosis give an example of an exception
Some types of green algae and slime mold, exist as enormous cells containing thousands of nuclei, the product of many rounds of mitosis without cytokinesis
What are the three main events of the cell cycle?
The three main events are interphase, during which the cell grows and replicates its DNA, mitosis, during which the DNA divides, and cytokinesis, during which the cytoplasm divides.
What happens during interphase
During interphase, a cell grows and produces proteins so that its normal biochemical functions proceed. DNA replicates during interphase as a cell prepares to divide
How does the mitotic spindle form, and what is its function?
The mitotic spindle is composed of microtubules associated with cytoskeleton proteins. The spindle originates from centrosomes that are at opposite ends of the cell. Spindle fibers grow across to join at the midline of the cell. The function of the mitotic spindle is to form “trackways” for the movements of chromosomes as cells divide.
What happens during each phase of mitosis
The events of mitosis include:
• Prophase: chromosomes condense and become visible; mitotic spindle forms
• Prometaphase: nuclear envelope breaks up; spindle fibers attach to kinetochores on each chromosome
• Metaphase: chromosomes line up on equator of cell
• Anaphase: sister chromatids separate and move to opposite poles of the cell
• Telophase: nuclear membranes reassemble around the daughter nuclei; chromosomes decondense; spindle disappears
- Distinguish between mitosis and cytokinesis
Mitosis is the division of duplicated chromosomes into new daughter nuclei. Cytokinesis is the division of cytoplasm and organelles into two new daughter cells and the separation of these cells.
