Chapter 11/12- Cell division Flashcards
Necessary for the growth of organisms, for wound healing, and to replace cells that are lost regularly, such as those in your skin and in the lining of your gut.
Cell Division
All species of organisms __________ and ____________ to pass on the hereditary information
Grow; Reproduce
Name 2 types of Cell Division
Bacterial Cell Division; Eukaryotic Cell Division
Bacteria divide as a way of
reproducing themselves
Although bacteria exchange DNA, they do not have a ______________ like eukaryotes
sexual cycle
All growth in a bacterial population is due to ___________________
division to produce new cells
reproduction of bacteria is
clonal
Each cell produced by cell division is an identical copy of the original cell
Clonal reproduction
Cell division in both bacterial and eukaryotic cells produces
two new cells with the same genetic information as the original
In Cell division in both bacterial and eukaryotic cells, what are essentials of the process which are the same,
duplication and segregation of genetic information into daughter cells, and division of cellular contents
___________have a genome made up of a single, circular DNA molecule found in the nucleoid
Bacteria
Circular DNA of bacteria held together by
structural maintenance of chromosome , (SMC) proteins
In eukaryotes the ________ and _________ proteins are SMC proteins
cohesin and condensin proteins are SMC proteins
Causes replication of DNA and division of cell into 2 cells
Binary Fission
A sexual reproduction by division of 1 cell or body into 2 equal or nearly equal parts
Binary fission
Binary Fission occurs in
Bacteria
produces two identical cells with the same genetic information as the original cell
Binary Fission
What are the steps of Binary Fission
- DNA replication
- Cell Elongation
- Cell Division
Binary Fission: DNA replication
Describe.
- Begins with the replication of the bacterial DNA at a specific site—the origin of replication (origin point)
- Enzymes for DNA duplication continue until they meet each other (finished replicating)
- Origin point of each DNA are in opposite directions: DNA proceeds both directions around the circular DNA to a specific site of termination
Binary Fission: Cell Elongation
Describe.
- As DNA replication completes, the origin moves to opposite sides of the cell, causing elongation (growth) of the cell
- Nucleoids are assembled around each circular DNA
Binary Fission: Cell Division
Describe.
- Once DNA is segregated, the midline is cleared of remaining nucleoids and cell division occurs
- production of septum (the wall) occurring at the midpoint of the cell forms the cell wall for the daughter cells
- The septum will pinch pinch off
During replication, first the origin, then the rest of the newly replicated chromosomes are moved to opposite ends of the cell as two new nucleoids are assembled
The final event of replication is decatenation (untangling) of the final replication products.
After replication and segregation, the midcell region is cleared of daughter nucleoids, and division occurs.
The force behind chromosome segregation has been attributed to DNA replication itself, transcription, and the polymerization of actinlike molecules.
The cell’s other components are partitioned by the growth of new membrane and production of the septum (A wall between two cavities.) This process, termed septation, usually occurs at the midpoint of the cell
It begins with the formation of a ring composed of many copies of the protein FtsZ. Proteins assemble into ring and facilitate septation and cell division
chromosome segregation
Chromosome number varies among species (T/F)
True
Humans have _________ chromosomes and ________ pairs
46; 23
Eukaryotic DNA are packaged as ________________
chromosomes
Determines how a person’s body develops and functions
chromosomes
Human embryos missing even one chromosome
monosomy
Having an extra copy of any one chromosome
trisomy
Chromosomes are composed of ____________, a complex of DNA and protein with a significant amount of RNA
chromatin
Chromosomes are the site of _____________
RNA synthesis
Each chromosome contains a single _______________ that runs uninterrupted through the chromosome’s entire length
DNA molecule
Every 200 nucleotides =
DNA duplex (double strand)
DNA duplex (double strand) is coiled around a core of
eight histone proteins
Histones are ____________ charged because of an abundance of the basic amino acids _________ and ________. Thus, they are strongly attracted to the ___________charged phosphate groups of the DNA
positively ; arginine and lysine.
negatively
The complex of DNA duplex wound around a core of 8 histone proteins is termed
nucleosome
DNA is ________ charged while histones are ___________ charged
negatively
positively
The DNA wrapped in nucleosomes is further coiled into an even more compact structure called
solenoid
Solenoids form looped domains that form
densely packaged DNA
During mitosis, proteins are assembled into a _________ that provides a framework for the final level of compaction. This gives chromosomes their familiar X-shaped structure, and facilitates separation by the mitotic machinery
scaffold
The particular array or morphology of chromosomes an individual organism possesses is called its
karyotype
One complete set of chromosomes necessary to define an organism.
haploid (n)
refers to n number of chromosomes; one set of chromosomes
haploid (n)
For humans and many other species, the total number of chromosomes in a cell is called the ___________ number, which is twice the haploid number
diploid (2n)
For humans, the haploid number is ____ and the diploid number is ____.
23; 46
reflects the equal genetic contribution that each parent makes to offspring
Diploid chromosomes
Refers to similar structures that have the same evolutionary origin.
homologous
Refers to a pair of the same kind of chromosome in a diploid cell.
homologous
In a diploid each chromosome has a ___________
homologue
maternal and paternal chromosomes are referred to as _______________, and each 1 of the pair is termed ______________
homologous; homologue
Homologous chromosomes replicate themselves for ____________ and is held together by ___________
Cell division
cohesins
A protein complex that holds sister chromatids together during cell division.
cohesins
The loss of _________ at the centromere allows the anaphase movement of chromosomes.
cohesins
After replication, each chromosome is composed of two identical DNA molecules held together by a complex of proteins called
cohesins
Refers to either of the two identical copies (chromatids) formed by the replication of a single chromosome ________________, with both (2) copies joined together by cohesions (proteins) via a region called_____________
sister chromatids ; centromere
The region of a chromosome to which the microtubules of the spindle attach, via the kinetochore, during cell division.
centromere
Two replicas of a single chromosome held together at their centromeres by cohesin proteins after DNA replication.
sister chromatids
Composed of proteins found at the centromere that attach to microtubules during mitosis
kinetochore
Eventually 2 sister chromatids separate, ONE in each ____________ cell.
daughter cell
portion of DNA that is not expressed as RNA
Heterochromatin
portion of DNA that is expressed as RNA
Euchromatin
The repeating sequence of growth and division through which cells pass each generation, or growth and division of eukaryotic cells
requires the duplication of the genome, its accurate segregation, and the division of cellular contents.
Cell Cycle
5 stages of Cell Cycle
– G1 (gap 1) phase – S (synthesis) phase – G2 (gap2) phase – Mitosis – Cytokinesis
The primary growth phase of the cell
G1 (gap 1) phase
Longest phase of Cell Cycle
G1 (gap 1) phase
The phase in which the cell synthesizes a replica of the genome, or DNA is replicated
S (synthesis) phase
The second growth phase, where the cell is preparing for separation of the newly replicated genome, or DNA
G2 (gap2) phase
During this phase microtubules begin to reorganize to form a spindle for mitosis
G2 (gap2) phase
G1, S, and G2 together constitute _______________ , the portion of the cell cycle between cell divisions.
interphase
Phase of the cell cycle in which the SPINDLE apparatus assembles, binds to the chromosomes, and moves the sister chromatids apart.
Mitosis
The essential step in the separation of the two daughter genomes
Mitosis
5 stages of mitosis
prophase, prometaphase, metaphase, anaphase, and telophase
phase of the cell cycle when the cytoplasm divides, creating two daughter cells
Cytokinesis
involves growth and preparation for DNA synthesis
G1 phase
a copy of the genome is synthesized
S phase
prepares the cell for mitosis
G2 phase
replicated chromosomes are partitioned
mitosis
divides the cell into two cells with identical genomes.
cytokinesis
To distinguish the dividing phase from interphase, Mitosis and cytokinesis together are usually referred to collectively as
M phase
Cells often pause in G1 before DNA replication and enter a resting state called the
G0 phase
The stage of the cell cycle occupied by cells that are not actively dividing.
G0 phase
Most of the cells in an animal’s body are in this phase
Most cells are in this phase
G0 phase
All the events that happen during G1, S, and G2 phases
Interphase
Interphase prepares chromosomes for __________
mitosis
Interphase:
1) A point of constriction on the chromosome containing repeated DNA sequences that bind specific proteins.
2) These proteins make up a disklike structure called ______________
1) centromere
2) kinetochore
Interphase:
A disk-like protein structure bound to repeating DNA
sequences on the centromere
kinetochore
Interphase:
During mitosis, microtubules will attach at ___________ and pull the sister chromatids apart
kinetochore
Interphase:
In __________ phase, the replicated chromosomes will further condense ,
G2 phase
Interphase:
Chromosomes begin the process of condensation, coiling ever more tightly in __________ phase
G2 phase
Interphase:
In __________ phase, centrioles will replicate and tubulin will be synthesized (the two will form microtubules)
G2
Interphase:
Protein that forms microtubules.
Tubuiln
Interphase:
Involved in the rapid final condensation of the chromosomes that occurs early in mitosis
Special motor proteins
M phase: Mitosis (stages)
What am I?
- condensed chromosomes
- condensation process continues, or further condensation of chromosomes.
- Ribosomal RNA synthesis ceases when the portion of the chromosome bearing the rRNA genes is condensed.
- No further production of rRNA
Prophase
M phase: Mitosis (stages)
What am I?
- spindle apparatus will assemble
- two centriole pairs formed during G2 phase begin to move apart, forming between them an axis of microtubules (referred to as spindle fibers) until they reach opposite sides of the cell
Prophase
M phase: Mitosis—-> Prophase
In animal cell mitosis, the centrioles extend a radial array of microtubules toward the nearby plasma membrane when they reach the poles of the cell. This arrangement of microtubules is called an___________
Aster
M phase: Mitosis (stages)
What am I?
The nuclear envelope begins to break down
Prophase
M phase: Mitosis (stages)
What am I?
During the formation of the spindle apparatus, the nuclear envelope breaks down competley and the endoplasmic reticulum reabsorbs its components
Condensed chromosomes will attach to (spindle)microtubules via kinetochores
Prometaphase
M phase: Mitosis (stages)
What am I?
Occurs following the disassembly of the nuclear envelope.
Prometaphase
The transitional phase between prophase and metaphase during which the spindle(microtubules) attaches to the kinetochores of sister chromatids.
Prometaphase
M phase: Mitosis (stages)
What am I?
- Condensed chromosomes become attached to the spindle by their kinetochores
- Each chromosome possesses two kinetochores, one attached to the centromere region of each sister chromatid
Prometaphase
M phase: Mitosis (stages)
What am I?
As _____________ continues, a second group of microtubules grow from the poles of the cell toward the centromeres.
These microtubules are captured by the kinetochores on each pair of sister chromatids. This results in the kinetochores of each sister chromatid being connected to opposite poles of the spindle.
Prometaphase
M phase: Mitosis (stages)
What am I?
- Second group of microtubules attach to kinetochore on centromere (opposite from the first site)
- Results in microtubules attached to each side of the sister chromatids
Prometaphase
M phase: Mitosis (stages)
What am I?
Microtubules will pull all of the chromosomes to the center of the cell
Prometaphase
M phase: Mitosis (stages)
What am I?
The alignment of the chromosomes in the center of the cell
metaphase
M phase: Mitosis (stages)
What am I?
Third stage of mitosis _______________
metaphase
M phase: Mitosis (stages)
What am I?
The alignment of the chromosomes in the center of the cell run along the ____________________
metaphase plate
M phase: Mitosis (stages)
What am I?
Not an actual structure, but rather an indication of the future axis of cell division.
metaphase plate
M phase: Mitosis (stages)
What am I?
Shortest phase
anaphase
M phase: Mitosis (stages)
What am I?
Begins when the cohesin proteins holding sister chromatids together at the centromere are removed
anaphase
M phase: Mitosis (stages)
What am I?
Up to this point in mitosis, sister chromatids have been held together by cohesin proteins concentrated at the centromere
anaphase
M phase: Mitosis (stages)
What am I?
- Kinetochores are pulled toward the poles as the microtubules that connect them to the poles shorten
- Tubulin subunits are removed from the kinetochore ends of the microtubules, and progressively disassemble
- Chromatids are pulled ever closer to the poles of the cell.
Anaphase A
First stage of Anaphase
Anaphase A
Second stage of Anaphase
Anaphase B
M phase: Mitosis (stages)
What am I?
Poles move apart as microtubular spindle fibers physically anchored to opposite poles slide past each other, away from the center of the cell
Anaphase B
M phase: Mitosis (stages)—> Anaphase
The kinetochores are pulled by shortening microtubules (disassembly of tubulin), resulting in _______________________, the poles then
separate as microtubules _____________________
sister chromatids being pulled in opposite directions (poles)
pull back to opposite poles of the cell
M phase: Mitosis (stages)
What am I?
The nucleus re-forms during ________________________
telophase
M phase: Mitosis (stages)
What am I?
- Spindle apparatus is diassembled
- Microtubules broken down to tubulin
- Nuclear envelop forms around chromosomes on both sides
telophase
In this phase chromosomes uncoil for gene expression and rRNA production, resulting in reappearance of the nucleolus
Telophase
During telophase cytoplasmic organelles are ___________________
sorted into both daughter cells
M phase: Mitosis (stages)
What am I?
Cytoplasmic organelles are sorted into both daughter cells
Telophase
M phase: Mitosis (stages)
What am I?
Achieved by means of a constricting belt of actin filaments
In animal cells
Cytokinesis
In cytokinesis, a belt of actin filaments slide towards each other, pinching the middle of the cell together, a structure called the ______________________
cleavage furrow
The constriction that forms during cytokinesis in animal cells that is responsible for dividing the cell into two daughter cells.
cleavage furrow
In cytokinesis, the __________________will deepen until the cells pinch off to form 2 daughter cells
cleavage furrow
Division of the cytoplasm of a cell after nuclear division.
cytokinesis
The structure that forms at the equator of the spindle during early telophase in the dividing cells of plants and a few green algae.
cell plate
M phase: Mitosis (stages) —-> Cytokinesis (plants)
During telophase, center of expanding cell forms a _______________
cell plate
M phase: Mitosis (stages) —-> Cytokinesis (plants)
What is the function of the cell plate?
Will fuse with the membrane and divide the cell into 2
Where is the cell cycle process checked for accuracy and halted if there are errors?
Check Points
Cell cycle can be put on hold at specific points called
Check Points
HIGH LEVEL OF CONTROL that ensures proper division and high accuracy of chromosome replication
Check Points
Proteins that start or stop each phase of the cell cycle
Check Points
What are the 3 cell cycle check points
G1/S checkpoint
G2/M checkpoint
Spindle checkpoint
Halts the cycle to assess internal state of cell and integrates external signals
check points
A positive regulator of cell-cycle progression in the cytoplasm of dividing cells
maturation-promoting factor (MPF )
Research on the activation of frog oocytes led to the discovery of a substance that was first called
maturation-promoting factor (MPF )
The first MPF was discovered during
oocytes experiments
What experiment is this?
Cytoplasm taken from a variety of actively dividing cells from the M phase / injected in G1 phase of cell / prematurely began mitosis, or induced cell division when injected into oocytes
oocytes experiments
____________ taken from a variety of actively dividing cells from the _________ / injected in _________of cell / prematurely began ________, or induced ________ when injected into __________
Cytoplasm
M phase
G1 phase
mitosis
cell division
oocytes
Oocyte experiment
____________ taken from a variety of actively dividing cells from the _________ / injected in _________of cell / prematurely began ________, or induced ________ when injected into __________
Cytoplasm
M phase
G1 phase
mitosis
cell division
oocytes
A type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth.
mitosis
True or false
Cytoplasm from M phase contains a positive regulator that causes a cell to enter mitosis
True
MPF
True or False
MPF activity varied during the cell cycle
True
low in early G2,
rising throughout this phase,
and then peaking in mitosis
Two key aspects of MPF:
1) MPF activity varied during the cell cycle: ______ in early ____, _______ throughout this phase, and then ______ in mitosis
2) Enzymatic activity of MPF involved the __________________________
low
G2
rising
peaking
phosphorylation of proteins
MPF levels varied throughout the cell cycle this suggested _______________________ and that MPF probably had some sort of _______________ activity
Regulation of MPF
enzymatic (kinase)
MPF activity variation indicated _________
Phosphorylation of proteins in MPF indicated _____________
Regulation of MPF
enzymatic activity
Research in sea urchin embryos and surf clams uncovered several similar proteins named
cyclins
Any of a number of proteins that are produced in synchrony with the cell cycle and combine with certain protein kinases, at certain points during cell division.
cyclins
Do cyclins have kinase activity?
No
How are cyclins similar to MPF
Varied levels throughout cell cycle
Cyclins were found to bind to protein kinases called
cyclin-dependent kinase (Cdk)
Cyclin-dependent kinase, or CDK is expressed by what gene
CDC2 gene
cyclin plus cdc2 =
MPF
A protein kinase enzyme that is only active when complexed with cyclin.
cyclin-dependent kinase (Cdk)
composed of both a cyclin component and a kinase component.
MPF
cdc2 is a ___________
kinase, or protein
What is MPF composed of
cyclin and cdc2 (kinase)
The cyclin + cyclin-dependent kinase complex is
one type of ___________ , originally discovered in the oocyte experiment
MPF
Cyclins + their kinase counterparts (cdc2/cdk1/p34… etc) =
maturation (mitosis) promoting factor
Several cyclins and kinases exist and comprise a large family of ___________ & ______________
proteins and kinases
What is the purpose of the cyclin + kinase complex?
phosphorylation of proteins associated at each check point so that the cell cycle can continue
True or False
The cell cycle is controlled at three checkpoints
True
G1/S checkpoint
G2 /M checkpoint
Spindle checkpoint (late metaphase)
Allow the cycle to be delayed or halted when necessary.
checkpoints
The cell uses ____________ to both assess its internal state and integrate external signals
checkpoints
Passage through these checkpoints is controlled by
Cdk enzymes
The primary control point at which a cell “decides” whether or not to divide. Also called START and the restriction point.
G1/S checkpoint
Primary point at which external signals can influence events of the cycle
G1/S checkpoint
The phase during which growth factors affect the cycle and also the phase that links cell division to cell growth and nutrition.
G1/S checkpoint
External signals may trigger or inhibit the cell cycle at this checkpoint
G1/S checkpoint
G2/M checkpoint
The second cell-division control point, at which division can be delayed if DNA has not been properly replicated or is damaged.
G2 /M checkpoint
Passage through this checkpoint represents the commitment to mitosis.
G2 /M checkpoint
This checkpoint assesses the success of DNA replication and can stall the cycle if DNA has not been accurately replicated.
G2 /M checkpoint
Cdks active at this checkpoint termed as M phase-promoting factor (MPF)
G2 /M checkpoint
G2 /M checkpoint contains active cdks termed
M phase-promoting factor (MPF)
A Cdk enzyme active at the G2/M checkpoint.
M phase-promoting factor (MPF)
The third cell-division checkpoint, at which all chromosomes must be attached to the spindle. Passage through this checkpoint commits the cell to anaphase.
Spindle checkpoint
Ensures that all of the chromosomes are attached to the spindle in preparation for anaphase.
Spindle checkpoint
At this checkpoint all chromosomes are attached to spindles for anaphase, at which point the process is IRREVERSIBLE
Spindle checkpoint
Enzymes that accomplish this phosphorylation
Cdks
At what checkpoint does the activation of cdc2 / G1 cyclin cause the cell to continue on to S-phase
G1/S
At what checkpoint does activation of cdc2 / mitotic cyclin cause the cell to continue on to M-phase
G2/M
At what checkpoint does activation of APC (anaphase promoting complex) causes the cell to continue on to anaphase
Spindle checkpoint
A protein complex that triggers anaphase; it initiates a series of reactions that ultimately degrades cohesin, the protein complex that holds the sister chromatids together. The sister chromatids are then released and move toward opposite poles in the cell.
anaphase-promoting complex (APC)
1) What protein does anaphase-promoting complex (APC) mark for DESTRUCTION by adding ubiquitin (protein marker for degradation) ?
2) T/F
APC /C acts as a ubiquitin ligase
securin
true
Acts as an inhibitor of another protease called separase
securin protein
Securin protein acts as an inhibitor of another protease called
separase
Separase destroys ______________
cohesin
Protease which normally degrades cohesin, or the proteins that hold the sister chromatids together
separase
Activates the PROTEASE that removes the cohesins holding sister chromatids together, and it is necessary for the DESTRUCTION of mitotic cyclins to drive the cell out of mitosis
anaphase-promoting complex (APC)
Cyclins and kinases, or CDKs themselves are
activated via _______________________
phosphorylation
Growth factors act by triggering
intracellular signaling systems
______________ signals cause ______________ of Cdks
External
phosphorylation
A receptor tyrosine kinase (RTK) that initiates/activates a MAP kinase cascade to stimulate cell division
platelet-derived growth factor (PDGF).
When a tissue is injured, a blood clot forms, and the release of ____________triggers neighboring cells to divide, helping to heal the wound.
PDGF
T/F
PDGF is not a growth factor
False
It is a growth factor
1) Over how many different proteins function as growth factors?
2) These growth factor receptors often initiate MAP kinase cascades in which the final kinase enters the nucleus and activates__________________ by phosphorylation
3) Stimulates the production of G1 cyclins and the proteins that are necessary for cell-cycle progression
50
transcription factors
transcription factors
Cells that are not exposed to growth factors stop at _________, checkpoint and enter _______ phase.
G1 checkpoint
G0 phase
Cells remain dormant at this phase
G0 phase
The unrestrained, uncontrolled growth of cells in humans leads to the disease called
cancer
A disease of cell division—a failure of cell division control.
cancer
What happens when cells ignore these
checkpoints? (G1, G0)
Cancerous cells
The gene that produces the p53 protein
p53 gene
Monitors DNA integrity and halts cell division if DNA damage is detected.
p53 protein
Many types of cancer are associated with a damaged or absent
p53 gene
p53 gene is abundant during__________
G1 phase checkpoint
Determines chromosome integrity, checks for errors in copying DNA, DNA damage and mutations
p53 gene
Helps in cell repair mechanism
p53
p53 gene prevents the development of many mutated cells, and it is therefore considered a______________
tumor-suppressor gene
A gene that normally functions to inhibit cell division; mutated forms can lead to the unrestrained cell division of cancer, but only when both copies of the gene are mutant.
tumor-suppressor gene
p53 is also know as _________________
tumor-suppressor gene
Halts division of damaged cells, can also directs cell to kill itself
tumor-suppressor gene
p53 is entirely absent or damaged beyond use in the majority of __________________ cells
cancer
Causes cells to proliferate uncontrollably, leading to cancer
Abnormal P53 function or lack of P53 protein
Fails to stop cell division and repair DNA
Abnormal p53 protien
Genes that can, when introduced into a cell, cause it to become a cancer cell
oncogenes
A mutant form of a growth-regulating gene that is inappropriately “on,” causing unrestrained cell growth and division.
oncogene
Normal cellular genes that become oncogenes when mutated.
proto-oncogenes
Ex: PDGF receptor mutation causes receptor to
always be ‘on’ in the absence of ligand
The action of proto-oncogenes is often related to signaling by____________, and mutuation can lead to loss of _____________
Growth Factors
Growth Control
Encodes for proteins (Rb protein, p53 protein) that prevent uncontrollable cell division
Cause cancer when mutated
Tumor-suppressor genes
A gene that, when mutated, predisposes individuals to a rare form of cancer of the retina; one of the first tumor-suppressor genes discovered.
retinoblastoma susceptibility gene (Rb)
