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BIOL 2311 - Dr. Candas - Chapter 12 - THE CELL CYCLE
Terms in this set (153)
The cell theory
All organisms are made up of cells and all cells arise from pre-existing cells.
The process of creation of new cells by the division of pre-existing cells.
Who proposed that new cells arise by the splitting of pre-existing cells?
A young developing organism, or the stage after fertilization and zygote formation.
In the late 1800s, microscopic observations of _____ confirmed Virchow's hypothesis.
mitosis and meiosis
What are the two fundamentally different ways in which nuclei divide before cell division?
In animals, _____ leads to the production of eggs and sperm.
In sexually reproducing organisms, a special two-stage type of cell division in which one diploid (2n) parent cell produces haploid (n) cells (gametes) resulting in the halving of the chromosome number. (also called reduction division)
A haploid reproductive cell that can produce another haploid cell to form a zygote. Most multicellular eukaryotes have 2 ditinct forms: egg cells (ova) and sperm cells.
In eukaryotic cells, the process of nuclear division that results in the formation of 2 daughter nuclei genetically identical with the parent nucleus. Subsequent cytokinesis (division of the cytoplasm) yields two daughter cells.
The type of nuclear division that leads to the production of all other cell types.
Any type of cell in a eukaryotic organism besides the eggs, sperm, and their precursor cells. Also called body cells.
Division of the cytoplasm to form two daughter cells , typically occurring immediately after the division of the nucleus through mitosis or meiosis.
Mitosis and meiosis are responsible for one of the fundamental attributes of life: _____.
During _____ the genetic material is copied and then divided equally between two cells.
Mitosis can also be referred to as _____ because the resulting daughter cells are genetically identical to the parent cells.
_____ results in daughter cells that are genetically different from each other and have half the amount of genetic material as the parent cell.
(1) copy the DNA
(2) separate the copies
(3) divide the cytoplasm to create two complete cells
What are the general requirements for cellular replication?
(2) wound repair
(3) asexual reproduction
The key events for which eukaryotic cell replication (mitosis) is responsible for:
_____ is the basis of asexual reproduction.
Any form or reproduction in which the offspring inherit DNA from only one parent. It includes binary fission, budding and parthenogenesis.
Who first introduced the term mitosis?
in Greek, 'mitos' means _____
What cells did Flemming work with to study mitosis?
What other organism's cells were also widely used to study mitosis?
Who first coined the term 'chromosome'?
Chromosome literally means _____.
Gene carrying structure that consists of a single long molecule of double stranded DNA and associated proteins (histones, etc.) Most prokaryotes contain a single circular one while eukaryotes contain multiple nocircular (linear) ones located in the nucleus.
One of several positively charged (basic) proteins associated with DNA in the chromatin of eukaryotic cells.
histones are (acidic/basic)
histones are (positively/negatively) charged
_____ encodes the cell's hereditary information.
A length of DNA that encodes for a particular protein or ribonucleic acid (RNA) found in the cell.
As mitosis starts, the _____ condense into compact structures that can be moved around the cell efficiently.
Each of the DNA copies in a replicated chromosome
Once mitosis begins, most of the cohesin connections are removed except for those at a specialized region of the chromosome called the _____.
Constricted region of a replicated chromosome where the two sister chromatids are joined and the kinetochore is located.
Before mitosis, the two chromatids are joined along their entire length by proteins called ____.
Chromatid copies that remain attached at their centromere are referred to as ______.
M phase and interphase
Cells alternate between _____ and _____.
The most visually stimulating part of the cell cycle is during the _____.
mitotic or meiotic
The' M' in M phase stands for ____ or ____.
The chromosomes are viewed as discrete objects through a _____ only during the M phase.
The part of the cell cycle excluding the M phase during which no dramatic changes are visible by light microscopy.
The stage of the cell cycle during which the chromosomes are uncoiled into extremely long structures and are no longer stained as individual threads.
Cells spend most of their time in _____.
A compact chromosome is about _____ times shorter than its original length.
radioactive phosphorus in form of phosphates
Researchers used _____ to distinguish between cells that were replicating from those that were not.
(1) label the DNA as chromosomes were being copied
(2) wash away any radioactive isotope that hadn't been incorporated and remove the RNA which would also incorporate phosphorus.
(3) visualize the labelled newly synthesized DNA by exposing the treated cells to X-ray film. Emissions from radioactive phosphorus created a black dot in the film.
List the basic ideas behind Alma Howard and Stephen Pelc's experiment to detect active DNA synthesis.
synthesis phase (S phase)
The part of interphase during which replication of the genetic material takes place.
The orderly sequence of events that leads a eukaryotic cell through the duplication of its chromosomes to the time it divides.
Howard and Pelc
The term cell cycle was coined by _____.
_____ are powerful experimental tools because they can be manipulated much more easily than cells in an intact organism.
_____ cultures means that the cells of the culture are randomly distributed in the cycle.
Which technique was used to discover the gap phase
radioactively labeled thymidine
What substance is used in the pulse-chase assay to discover the gap phase in the cell cycle?
By radiolabeling the cells in the S phase using a pulse-chase assay of radioactively labeled thymidine, the cells in the S phase were marked. By observing these cells researchers noticed that mitosis did not immediately occur after the S phase and instead, there was a time lag/gap. This was called the G2 phase.
Briefly explain how the second gap phase was discovered.
By adding the times of the S phase, the G2 phase and the time for mitosis, it did not amount to the entire duration of the cell cycle. The only explanation for this discrepancy would have to be the existence of an additional gap phase G1 prior to the synthesis phase and after the M phase.
Briefly explain how the first gap phase was discovered.
The gap between the end of the M and the start of the S phase is called the _____.
The gap between the end of S and the start of the M phase is called the _____.
(1) M phase
What are the four phases of the cell cycle?
It depends on the cell type and growth conditions.
How many times longer is the G1 phase than the G2 phase?
Cells must prepare for division by replicating organelles and increasing in size.
What is the exact need for the gap phases?
(1) division of the nucleus
(2) division of the cytoplasm
What are the two distinct events that take place during the M phase?
_____ division results in two daughter cells.
During _____, the chromatin of each chromosome is in a "relaxed" or uncondensed state, forming long, thin strands.
The two sister chromatids are attached to each other at the _____.
Name the five stages of mitosis:
(1) chromosomes condense
(2) spindle apparatus begins to form
What events happen during prophase?
Chromosomes become first visible in the light microscope during _____.
A structure that produces mechanical forces that (1) move replicated chromosomes during early mitosis and (2) pull chromatids apart in late mitosis.
The spindle apparatus consists of _____, components of the _____.
microtubule organizing center
What is the full form of MTOC?
In eukaryotic organisms, microtubules originate from the _____.
_____ define the two poles of the spindle and produce a large number of microtubules.
During prophase, some of the microtubules extend from each spindle pole and overlap with one another and they are called _____.
In an animal cell, the MTOC is called the ____.
The centrosome contains a pair of _____.
During prophase in animal cells, the spindle begins to form by moving _____ to opposite sides of the nucleus.
(1) nuclear envelope breaks down
(2) microtubules contact chromosomes at kinetochores
(3) chromosomes BEGIN to move to the middle of the cell
What are the events that take place during prometaphase?
A protein complex at the centromere where microtubules attach to the chromosome. It contains motor proteins and microtubule-binding proteins that are involved in chromosome segregation during M phase.
How many kinetochores are on each chromosome during prometaphase?
The microtubules that attach to the kinetochores during prometaphase are known as _____.
kinesin and dynein motors
What specialized proteins are recruited at the kinetochore that walk the chromosomes up and down the microtubules?
The kinetochore is attached to the ____ end of the microtubule.
(1) chromosomes complete migration to the middle of the cell
What event(s) happen during metaphase?
The imaginary plane at the middle of the cell between the two poles of the cell at which the chromosomes line up during before separation is called the _____.
The formation of the spindle apparatus is complete during _____.
The _____ that extend from each spindle overlap at the middle of the cell during metaphase and form pole-to-pole connections.
During metaphase, each chromosome is held by _____ reaching out from opposite poles and exerting the same amount of tension or pull.
Mitotic and meiotic microtubules that have arisen from the two spindle poles and interact with proteins on the plasma membrane.
The spindle poles are partly held in place because of the _____ that extend from the MTOCs and interact with proteins on the cell membrane.
The alignment of the chromosomes at the metaphase plate results from the growth and shrinkage of the attached ____.
No, when chromosomes reach the metaphase plate, the shrinkage of the microtubules at the MTOCs is balanced by their slow growth at the the kinetochores.
Do the kinetochore microtubules stop growing/shrinking when they attach to chromosomes at the metaphase plate?
(1) The cohesins that are holding the sister chromatids together at the centromere split.
(2) Sister chromatids separate and daughter chromosomes are pulled to the opposite poles of the spindle apparatus.
What are the events that take place during anapase?
What happens to the chromosome number in the cell during anaphase?
(1) the daughter chromosomes move to opposite poles via the attachment of kinetochore proteins to the shrinking kinetochore microtubules.
(2) the two poles of the spindle are pushed and pulled farther apart with the help of the motor proteins in the overlapping polar microtubules, astral microtubules and membrane.
Explain the two types of movements that occur during anaphase.
(1) the nuclear envelope that dissolved in prometaphase reforms around each set of chromosomes
(2) the chromosomes begin to de-condense
What are the events that take place during telophase of mitosis?
Cylindrical structures that comprise microtubules located inside animal centrosomes.
Once two independent _____ are formed, mitosis is complete.
fluorescently labeled tubulin subunits
Scientists used _____ to study the mechanism for the movement of chromosomes during anaphase.
alpha-tubulin and beta-tubulin dimers
Microtubules are composed of _____ and _____.
(1) Biologists introduced fluorescently labeled tubulin subunits to make the kinetochore microtubules visible.
(2) At the beginning of anaphase, researchers marked a region of the microtubules with a laser to permanently bleach a section.
(3) As anaphase progressed they observed that (a) The darkened (bleached) region appeared to remain stationary and (b) the chromosomes moved closer to the darkened region of the microtubules, eventually overtaking them.
Briefly explain how scientists figured out the mechanism for the mitotic spindle movement.
The _____ has a crown of protein fibers projecting outwards at the centromere region of the chromosome.
At which end of the microtubules does the dissembling take place during anaphase?
During anaphase, to which end of the kinetochore microtubules does each chromosome travel?
The chromosomes are each pulled to their respective spindle pole by the _____ of kinetochore microtubules.
In plants _____ left over from the spindle help define and organize the region where the new plasma membranes and cell walls will form during cytokinesis.
In plants, vesicles from the _____ carry components to build a new cell wall to the middle of the dividing cell during cytokinesis.
In plants, during cytokinesis, vesicles carrying components to form the new cell wall move along the _____ via motor proteins.
A flattened sac-like structure formed in the middle of a dividing plant cell from Golgi-derived vesicles containing cell-wall materials, which ultimately divides the cytoplasm into two separate cells.
In animals and many eukaryotes, cytokinesis begins with the formation of a _____.
(1) A ring of actin filaments forms just inside the plasma membrane in the middle of what used to be the spindle. (2) Myosin motor proteins bind to these actin filaments and use adenosine triphosphate to contact in a way that causes actin filaments to slide.
(3) As myosin moves the ring of actin filaments on the inside of the plasma membrane, the ring shrinks in size and tightens.
(4) Since the ring is also attached to the plasma membrane, the shrinking ring pulls the plasma membrane with it and causes it to pinch inwards until cell division is over.
Explain cleavage furrow formation and how it leads to cytokinesis in the animal cell.
A process of cell division used for asexual reproduction in many prokaryotic cells. The genetic material is replicated and partitioned to opposite sides of a growing cell, which is then divided in half to create twp genetically identical cells.
As the bacterial chromosome is being replicated, _____ attach to the copies and separate them to opposite sides of the cell.
(1) DNA is copied and protein filaments are attached
(2) DNA copies are separated; ring of proteins form
(3) ring of proteins draws in membrane
(4) fission complete
Briefly explain the process of binary fission
nerve cells and muscle cells
Which two types of mature human cells do not divide at all?
Differences in the duration of cell division are due to variations in the length of the _____.
Most non-dividing cells are usually permanently stuck in _____.
Most rapidly dividing cells do not have a _____ phase.
G0 stage, post-mitotic
If a cell is permanently arrested in the the G1 stage, it is actually said to be in ____ or _____ stage because they have now exited the cell cycle.
human liver cells
Unless there is damage, _____ cells replicate only once a year. However if there is damage, they replicate once every one or two days until repair is accomplished.
_____ experiments helped in studying cell-cycle regulation.
South African clawed-frog, Xenopus Laevis
The cells of the _____ were useful in studying cell-cycle regulation.
MPF (M-phase promoting factor)
The factor that initiates M-phase in all eukaryotic cells.
(1) a cyclin-dependent protein kinase (Cdk) (an enzyme that catalyzes the transfer of a phosphate group from ATP to a target protein or phosphorylation; this enzyme has a constant concentration throughout the cell cycle)
(2) cyclin ( their concentrations fluctuate throughout the cell cycle building up steadily during interphase and peaking at the beginning of the M phases)
What are the two subunits of the MPF?
The phosphorylation of one site of the MPF's Cdk subunit activated the kinase, but when the second site is phosphorylated, it is inactivated.
How is the MPF turned on and how is it regulated?
(1) Negative feedback: The slowing or shutting down of a process by one of its events. MPF is turned off by an enzyme complex that is activated by events in mitosis.
(2) An enzyme complex is activated in anaphase which attaches to small proteins called ubiquitins to MPF's cyclin subunit, thus marking it. All such marked cyclins are then destroyed by specific proteins called the proteasomes, thus reducing the conc. of cyclin.
How is the MPF turned off?
Cells that don't divide since they are arrested in G0 are also known as:
Any of several points in the cell cycle at which progression of the cell through the cycle can be regulated.
A mass of cells formed by uncontrolled cell division: can be malignant or benign.
(1) cell size should be adequate
(2) nutrients should be sufficient
(3) social signals are present
(4) DNA should be undamaged
What is verified at the G1 checkpoint?
signaling molecules from other surrounding cells that should be present in order for the cell to pass through the G1 checkpoint and successfully divide
The protein p53 which is a tumor suppressor activates genes that either stop the cell cycle until the damage can be repaired or cause the cell's programmed controlled destruction or apoptosis.
What happens if the DNA is damaged at the G1 checkpoint?
(1) chromosomes have replicated successfully
(2) DNA is undamaged
(3) activated MPF is present
What does the G2 checkpoint check for?
(1) chromosomes have attached to the spindle apparatus (metaphase checkpoint: if this didn't exist, some chromosomes may not separate correctly leading to too many or too few chromosomes)
(2) chromosomes have properly segregated and that MPF is absent (it checks the progression into G1 phase)
What does the M phase checkpoint look for?
programmed cell suicide is also called _____
A disease caused by uncontrolled cell division
(1) defects that make the proteins required for cell division active when they shouldn't be
(2) defects that prevent tumor suppressor genes from shutting down the cell cycle
What 2 defects can lead to cancer?
The _____ protein is a key component in the signal transduction system. Defects in this cause unwanted triggering of mitosis.
A tumor that is actively growing and disrupting local tissues and is spreading to other organs is called _____.
A mass of abnormal tissue that appears due to unregulated growth but does not spread to other organs.
Spread of cancerous cells from their site of origin to distant sites in the body where they may establish additional tumors.
Most types of cancer cells involve defects in the _____.
The general principle that individual cells must be allowed to divide only when their growth is in the best interests of the organism as a whole.
polypeptides or small proteins that initiate cell division
The liquid portion of the blood that remains after the cell fragments and blood cells have been removed.
A tumor suppressor protein that blocks the activity of E2F and behaves as one of the key molecules that enforces the G1 checkpoint.
A key regulatory protein that is produced in G0 cells on arrival of growth factors, which when activated, triggers the expression of genes required for the S phase.
(1) growth factors arrive from other cells
(2) growth factors stimulate the production of E2F and G1 cyclins
(3) Rb binds to E2F, inactivating it and the G1 cyclins begin forming cycin-cdk dimers with the cdk component initially inactivated.
(4) The inactivating phosphate group on the cyclin is removed and the active cdk now phosphorylate the Rb
(5) this release the E2F
(6) E2F triggers production of S-phase proteins.
explain detailed G1 checkpoint mechanism
(1) cyclin over-production due to excessive amounts of growth factors or a defective signal pathway (too much Ras, etc)
(2) defective Rb
explain how the G1 checkpoint can go wrong and cause cancer
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