Unit 3: Cell Cycle Flashcards
Represents a self-regulated sequence of events that controls cell growth and cell division
Cell Cycle
What is the goal of cell cycle?
To produce two daughter cells, each containing chromosomes identical to those of the parental cell
This is the different steps and phases for cells to replicate.
Cell Cycle
What are the two principle phases of the cell cycle?
Interphase
Mitosis
This phase generally represents the continuous growth of the cell where the cell makes a copy of its DNA or DNA Replication.
Interphase
Cells spend most of their life in what phase?
Interphase
What are the three phases of Interphase?
G1
S
G2
The phase characterized by the partition of genome where cell separates its DNA into 2 sets and divides its cytoplasm forming 2 new cells.
M Phase (Mitosis)
The phase wherein cell divides into 2 new daughter cells.
Cell Division
What are the three cell types?
Labile Cells
Stable Cells
Permanent Cells
The cells that want to grow and divide in order for them to carry out their function.
Labile Cells
What phases in the interphase do labile cells go through?
G1, S, G2, M Phases
Give three examples of labile cells.
- Epithelium of Skin
- Lining of the Urinary Tract (Ureter, Bladder, Urethra)
- Lining of the Gastrointestinal Tract
These are the cells that want to stay at the G1 phase, but if there are conditions that stimulate them to proceed with the S Phase and G2, they will eventually grow and divide.
Stable Cells
Stable cells want to stay at what phase?
G1
What are two examples of stable cells?
- Liver Cells
- Renal Tubules (Proximal Convoluted Tubule, Distal Convoluted Tubule, Cells of Loop of Henle)
Permanent Cells are also known as…
Amitotic Cells
These are the type of cells that undergo a period of cell cycle and end there.
Permanent Cells
True or False: Permanent Cells die with us
True
These are the type of cells that don’t proceed to the cell cycle anymore once they reach maturity.
Permanent Cells
What are the three examples of permanent cells?
- Neurons
- Cardiac Muscle
- Skeletal Muscle Fibers
The checkpoints were proposed by who? (2)
Leland Hartwell
Ted Weinert
Internal quality control mechanisms represented by biochemical pathways that control transition between cell cycle stages
Checkpoints
These monitor and modulate the progression of cells in response to intracellular or environmental signals.
Checkpoints
The stage in the eukaryotic cell cycle at which the cell would examine the internal and external cues to decide whether or not to move forward.
Checkpoints
The checkpoints are activated by a ___________________ that recognize a cell anomaly or problems in the cell.
system of sensors
Defined as the failure to arrest the cell cycle before or at mitosis, resulting in aberrant chromosome segregation
Mitotic Catastrophe
Caused by malfunction of cell cycle checkpoints and may lead to cell death and tumor cell development
Mitotic Catastrophe
Malfunction of cell cycle checkpoints may lead to: (2)
Cell Death
Tumor Cell Development
Cell death occurs by the activation of _______________ cycle where there is irreparable damage observed.
Apoptotic Cycle
Cells that fail to execute the apoptotic cycle in response to either DNA or mitotic spindle damage are likely to divide asymmetrically or unevenly in the next round of cell division. This would lead to a generation of __________ cells or cells that contain abnormal number of chromosomes.
Aneuploid Cells
The mitotic catastrophe may be regarded as one of the mechanisms contributing to _______________________.
Oncogenesis or Tumor Development
Malignant cells lose their _____________, wherein cells would inhibit their division when in contact with other cells.
Contact Inhibition
Malfunction of the restriction checkpoint may be facilitated by the viral proteins of several cancer-causing viruses, such as the _____________.
T-antigen of simian virus (SV40) that binds to pRb
This is a tumor suppressor and it suppresses the formation of tumor cells and it plays a role in the negative control of cell cycle.
pRb or Retinoblastoma Susceptibility Protein
How does the negative control in pRb work?
Blocks entry to S phase (to prevent replication of damaged DNA)
True or False: This binding alters the configuration of the pRb-T-antigen complex and renders the restriction checkpoint inoperable, thus facilitating the cell’s progression from the G1 to S phase of the cell cycle.
True
How many hours does it take for the G1 Phase to occur?
9 to 12 hours
How many hours does it take for the S Phase to occur?
7.5 to 10 hours
How many hours does it take for the G2 Phase to occur?
3.5 to 4.5 hours
True or False: No cell ever stays at the G1 Phase.
False
In this phase, the cell gathers nutrients and synthesizes RNA and proteins necessary for DNA synthesis and chromosome replication.
G1 Phase
What is the longest and most variable phase of Interphase?
G1
In this phase, the cell is doubling its molecular composition (the organelles it contains) such as organelles and biomolecules.
G1 Phase
In the G1 Phase, what molecular compositions are doubled?
Biomolecules
Organelles
This checkpoint monitors the integrity of the newly replicated DNA.
G1 DNA-Damage Checkpoint
True or False: If the checkpoint detects high levels of tumor suppressing protein (P53), the cell is still allowed to proceed to the next phase because the protein turns off the checkpoint operation.
False
The checkpoint that is sensitive to the size of the cell, the state of the cell’s physiologic processes, and its interactions with extracellular matrix.
Restriction Checkpoint
Restriction checkpoints are mediated by interactions between ______ and a family of _____, which are proteins that prevent cell division.
pRB; E2F
True or False: In normal cells, proper interaction between pRb and E2F turns off many genes and blocks cell-cycle progression.
True
Damage in the DNA is collectively termed as “__________________.”
Thymine Dimers
What may cause Thymine Dimers in the DNA?
UV Light
True or False: There is no DNA damage if there is an expression of proteins that functions as inhibitors of cell division.
False
In this stage of interphase, the DNA is replicated.
S Phase
In the S Phase, DNA is replicated from ____ chromosomes to ______ chromosomes.
46; 92
In this phase, the cell is allowed to synthesize a complete copy of the DNA in its nucleus.
S Phase
In this phase, the DNA of the cell is doubled and new chromatids are formed that will become obvious at the prophase stage of the mitotic division.
S Phase
Humans are __________ organisms.
Diploid
When the chromosome condenses, newly formed DNA or chromosomes or new chromatids that appear or were constructed in the S phase, would be visible in the __________ stage.
Prophase Stage
Chromosome replication is initiated at many different sites along the chromosomal DNA
Replicon
DNA-damage checkpoint that detects mispairing
S Phase Checkpoint or S DNA-damage Checkpoint
Period of cell growth and reorganization of cytoplasmic organelles before entering the mitotic cycle
G2 Phase
The cell prepared for cell division and examines its replicated DNA in preparation for cell division
G2 Phase
In this phase, cell double checks for mispairing and duplicated chromosome for error making any needed repairs.
G2 Phase
What enzymes function in checking for mispairings and duplicated chromosomes for errors making any needed repairs?
DNA Polymerase I and III
True or False: G2 Phase can synthesize at rapid speeds.
True
What is the nature of the nuclear membrane?
Phospholipid Bilayer
This signals that the chromosomes are ready to be divided to form chromatin, making the division of the nucleus possible.
Proteolytic Cleavage
What are the three proteins found in the nucleus?
H3A
Lamine Protein
Nuclear Pore Protein
The checkpoints at this stage monitor the DNA quality that is produced in the S phase
G2 Phase Checkpoint
In this checkpoint, the unreplicated DNA checkpoint would prevent the replication of the cell into M phase before DNA synthesis is complete. It would not allow the cell to continue to M phase unless DNA synthesis is complete.
G2 Phase
True or Phase: M Phase lasts about 8 hours.
False
(1 hour)
Mitosis always include what processes? (2)
Karyokinesis
Cytokinesis
Division of Nucleus
Karyokinesis
Division of Cytoplasm
Cytokinesis
Karyokinesis is possible due to _______________________ in G2.
Proteolytic Cleavage
The stage where formation of the sister chromatids, also called daughter chromosomes, occur.
Prophase
Sister chromatids may also be called…
Daughter Chromosomes
The phase where centromeres or centrioles are formed.
Prophase
What are the structural proteins forming centrioles?
MTOC - Microtubule Organizing Centers
What are the two fibers bound to the centrioles?
Polar Fibers
Astral Fibers
What is the shorter fiber? (Polar Fibers
or Astral Fibers)
Astral
What fiber has an affinity to the kinetochore (it has hooks that bind to the kinetochores and try to pull them in opposite directions)?
Polar Fibers
What is the longer fiber? (Polar Fibers
or Astral Fibers)
Polar Fiber
Polar fibers is a type of ___________ protein.
Structural
Polar fibers are attached to the _______________.
centromere
There are proteins in the centromere called __________________.
Kinetochores
When the polar fibers are pulling sister chromatids in opposite directions, the ____________________ is created
metaphase plate
In this phase, sister chromatids have already been separated.
Anaphase
In pulling the sister chromatids apart, the centrioles are assisted by proteins called ________________.
Motor Proteins
As the MTOCs are trying to pull the daughter chromosomes form teacher, there is a tension being created in the middle, hence forming the _________________________ seen in the telophase
cleavage furrow
In this phase, cleavage furrow is formed
Telophase
During the formation of cleavage furrow, why is the cell not ripping apart?
Contractile Proteins (Actin and Myosin)
True or False: All cells undergo cell division.
False
What are the two specific checkpoints of the M Phase?
- Spindle-assembly checkpoint
- Chromosome segregation checkpoint
This is also known as the resting phase.
G0 Phase
The reserve stem cell population belongs to what phase?
G0 Phase
Activation of the reserve stem cell population may be induced by what events? (3)
- Normal Wound Healing
- In repopulation of the seminiferous epithelium after intense acute exposure of the testis to X-irradiation
- During regeneration of an organ, such as the liver, after removal of a major portion.
What are the three main checkpoints of the cell?
- Cell Growth Checkpoint
- DNA Synthesis Checkpoint
- Mitosis Checkpoint
This checkpoint occurs toward the end of growth phase 1 (G1) and checks whether the cell is big enough and has made the proper proteins for the synthesis phase.
Cell Growth Checkpoint
This checkpoint occurs during the synthesis phase (S) to check whether the DNA has been replicated correctly.
DNA Synthesis Checkpoint
This checkpoint occurs during the Mitosis Phase (M) and checks whether the mitosis is complete.
Mitosis Checkpoint
Identify the Mitotic Phase described:
Replicated chromosomes condense and become visible
Prophase
Sister chromatids are held together by the ring of proteins called ____________ and the ______________.
Cohesins; Centromeres
True or False: In the formation of sister chromatid, centromeres/centrioles/MTOC are already observed.
True
In Prophase, what is the state of the nucleus?
Degraded
In a chromosome, what is the old strand?
Left
In a chromosome, what is the new strand?
Right
What is the chromosome composed of?
DNA
Chromatin
Formation of centromeres or centrioles at the polar end occurs in what phase?
Prophase
How many chromosomes are present in the Prophase stage?
92 chromosomes
Identify the Mitotic Phase described:
The nuclear envelope begins to disintegrate into small transport vesicles and resembles the sER
Prometaphase
This is also called late prophase.
Prometaphase
Identify the Mitotic Phase described:
The nucleolus, which may still be present in some cells, also completely disappears
Prometaphase
A highly specialized protein complex called a ____________________ appears on each chromatid opposite to the centromere.
kinetochore
This phase begins as the mitotic spindle, consisting of three types of microtubules, becomes organized around the microtubule-organizing centers (MTOCs) located at opposite poles of the cell.
Metaphase
What are the three types of microtubules?
Polar Microtubules
Astral Microtubules
Kinetochore Microtubules
What directs the movement of the chromosomes to a plane in the middle of the cell?
Kinetochore microtubules and their associated motor proteins
The phenomenon wherein the chromosomes move to the plane in the middle of the cell.
Equatorial or Metaphase Plate
When the polar fibers are pulling them in opposite directions, what is created?
Metaphase Plate
This phase begins at the initial separation of sister chromatids.
Anaphase
The centrioles are assisted by proteins called __________________ when pulling the sister chromatids apart.
motor proteins
This phase is marked by the reconstitution of a nuclear envelope around the chromosomes at each pole.
Telophase
What phase is described below:
Chromosomes uncoil and become indistinct except at regions that will remain condensed in the interphase nucleus
Telophase
What phase is described below:
Nucleoli reappear, and the cytoplasm divides to form two daughter cells.
Telophase
True or False: Mitosis forms two identical cells.
True
Formation of cleavage furrow occurs in what phase?
Telophase
This is a process in which gametes or sex cells are produced either egg or sperm cell. This process involves two sequential nuclear divisions. This is followed by cell division producing gametes containing half the number of chromosomes and half the DNA content found in somatic cells.
Meiosis
True or False: The cytoplasmic events of meiosis in males and females are the same.
False
True or False: The nuclear events of meiosis in males and females are the same.
True
This pertains to the chromosome number being reduced from diploid to haploid and the amount of DNA being reduced from 4D to 2D.
Reductional Division
Reductional Division occurs in what phase of meiosis?
Meiosis I
Equatorial Division occurs in what phase of meiosis?
Equatorial Division occurs in what phase of meiosis?
In this phenomenon, there is no DNA replication. The number of chromosomes remain at (1n), although the amount of DNA represented by the number of chromatids is reduced to (1d).
In this phenomenon, there is no DNA replication. The number of chromosomes remain at (1n), although the amount of DNA represented by the number of chromatids is reduced to (1d).
What are the five stages under Prophase I?
- Leptotene
- Zygotene
- Pachytene
- Diplotene
- Diakinesis
An extended phase in which pairing of homologous chromosomes, synapsis (close association of homologous chromosomes), and recombination of genetic material on homologous chromosomes is observed.
Prophase I
What are the three primary processes occurring among the homologous chromosomes during Prophase I?
- Pairing of Homologous Chromosomes
- Synapsis
- Recombination of genetic material
This refers to the close association of homologous chromosomes.
Synapsis
This is characterized by the condensation of chromatin and by the appearance of chromosomes.
Leptotene
Should a normal cell have 92 chromosomes?
no
In the Leptotene stage, sister chromatids condense and become connected with each other by ______________.
meiosis-specific cohesion complexes
In this stage of Prophase I, pairing of homologous chromosomes of maternal and paternal origin is initiated.
Leptotene
In this stage of Prophase I, synapsis begins and continues throughout Pachytene.
Zygotene
What complex is formed in the Zygotene stage?
Synaptenomal Complex
Synapsis is completed in this stage.
Pachytene
Crossing over occurs early in this stage and involves the transposition of DNA strands between two different chromosomes.
Pachytene
Early in this stage, the synaptonemal complex dissolves, and the chromosomes condense further.
Diplotene
In this stage, the homologous chromosomes begin to separate from each other and appear to be connected by newly formed junctions.
Diplotene
In the Diplotene stage, homologous chromosomes begin to separate from each other and appear to be connected by newly formed junctions between chromosomes called…
Chiasmata
True or False: In the Diplotene stage, sister chromatids are separated from each other.
False
In this stage, the homologous chromosomes condense and shorten to reach their maximum thickness. The nucleolus also disappears while the nuclear envelope disintegrates.
Diakinesis
In this phase, paired chromosomes are aligned at the equatorial plate with one member on either side.
Metaphase I
True or False: In Metaphase I, homologous chromosomes are still held together by chiasmata.
True
True or False: Once the nuclear envelope has broken down, the spindle microtubules begin to interact with the chromosomes through the multilayered protein structure which is usually positioned near the centromere.
True
True or False: In Anaphase I and Telophase I, the centromeres split.
False
In this phase, a maternal or paternal member of each homologous pair, now containing exchanged segments, moves to each pole.
Anaphase & Telophase I
True or False: Meiosis forms genetic diversity.
True
Inactivated X chromosomes seen in female somatic cells present adjacent to the nuclear membrane.
Barr Body
Small, well-defined body which stains intensely with nuclear dyes.
Barr Body
Present in a large proportion of nuclei of female origin and absent in male nuclei.
Barr Body
What is the average size of the Barr Body estimated in nuclei of buccal mucosa and in sections of several human tissues?
0.7 × 1.2 μ
Major phases of Cell Cycle
Three major phenomena that occurs in the interphase
Name one important phenomenon that occurs in the G.
What is doubled in the cell during G1?
In the S phase, what is the most important part of the central dogma that occurs?
In the S phase, there is a certain type of DNA damage that is corrected, what is that damage?
Give an example of a situation where formation of thymine dimers is induced.
What’s the most important step that occurs in the G checkpoint?
Finding mispairs, proteolytic cleavage
Finding mispairs, proteolytic cleavage
Why is there a need for proteolytic cleavage?
To make cellular division possible
Karyokinesis
Nuclear
What do you call the step of nuclear division?
Karyokinesis
Give an example of nuclear membrane proteins that are cleaved in G2.
H3A
Lamin
Nuclear Pore
Another term for centrioles.
Microtubule Organizing Center
Who assists the polar fibers to move into opposite directions of the cell?
Motor Proteins
In what part of the chromosome is the kinetochore attached?
Centromere
Between the astral fibers and the polar fibers, which one attached to the kinetochore?
Polar
Astral fibers and polar fibers are structural proteins, TRUE or FALSE?
True
Two fibers attached to centrioles
Polar, Astral
Generally, once the cells are pulled apart we move from prophase to?
Metaphase
In what phase does the lining of chromosomes in the centromere occur?
Metaphase
Once the cells are pulled apart, they should be ripped apart. Why does that not happen?
Cleavage furrow with actin and myosin
T or F. All cells undergo cell cycle even after maturation.
False
Two biological composition of chromatin
DNA and histone proteins
