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Cell Bio Exam 4
Terms in this set (67)
What is the cell cycle?
the events that occur in the cell
What happens in G1 (gap phase)?
cell growth happens (producing proteins, etc., and preparing for S) diploid
What happens in S phase?
DNA replication, tetraploid
What happens in G2 phase?
prepares for mitosis
What is mitosis?
prophase, metaphase, anaphase, telophase (purpose to separate chromosomes), cytokineses (cell goes back to G1)
What are the points of cell cycle control?
regulated by extracellular and internal signals, nutrient availability (plenty of nutrients are likely to progress through cell cycle)
What is START and what is the restriction point?
in yeast, major regulatory point in cell cycle that occurs late in G1, cell then is committed to entering S and undergoes one cell division( nutrients, cell size, mating factors trigger movement)
What is the G0 phase?
If the cell does not receive the go ahead for G1, it goes to G0 where it does not replicate and cell death happens
What are cell cycle checkpoints and what sorts of events influence them?
Late in G1(don't want to replicate and give cell time to repair), late in S (make sure replication is complete), late in G2 (double check no mutations before dividing), M (make sure chromosomes separate correctly)
If M fails, could lead to downsyndrome
What are cell cycle checkpoints?
Need to be able to sense if DNA has been damaged and stop cell cycle until DNA problem has been fixed
What is MPF?
discovered in frog eggs, induces entry of cells into M phase, responds by Progesterone and goes into M which goes into G2 which then leads into back into M
What are cyclins?
protein important with moving through restriction point by going from one thing to the next
What is a cdc mutant?
temp sensitive mutant in budding yeast
occurred in G1= cells deficient inactively
What is a cdc28 mutant and where does it act?
trapped in G1, loss of function mutations; normal function moves through cycle
What is a cdc2 mutant?
can't enter M, thinking it can require at start
cdc2 and 28 same gene-- test via complementation
What is cdk1?
master regulator of eukaryotic cells
What are cdk's?
cyclin dependent protein kinase's that control the cell cycle of all eukaryotic cells
What does cdk 4,6/CycD do?
goes through restriction point and phosphorylates the Rb protein.
Rb is transcriptionally regulated protein that mediates control of cell cycle progression
What does Cdk 2/ CycE do?
Goes from G1 to S
What does cdk1/CycB (MPF) do?
goes from G2 to M
What does Rb protein do in the presence of Cdk4,6/CycD?
represses transcription by E2F until it's active
normal function: inhibits progression in cell cycle and suppresses tumor
What is a mutant Rb?
loss of function, not an oncogene
What would uncontrolled expression of cyclinD lead to?
cancer, gain of function always being produced = oncogene
What do cdk2/cyclinE control?
progression into S phase and influence chromatin condensation, nuclear envelope breakdown, fragmentation of Golgi, spindle formation
What is ATM?
associated with double stranded breaks, signals kinases, inhibits cdc25, cdk2 inhibited causing G1 and S phase arrest and initiates DNA damage checkpoints
What is ATR?
associated with single stranded breaks, signals kinases, inhibits cdc25, cdk1 inhibited causing G2 arrest
What is cell proliferation?
regulated by growth factors and variety of signals that act to inhibit cell cycle progression
What is p53?
transcription factor that functions in G1 arrest and responds to ATM and transcribes p21 which causes activity to halt and causes G1 arrest
What is the spindle assembly checkpoint and what abnormal situation does it help prevent?
monitors the alignment of chromosomes on the metaphase spindle
Presence of a single unaligned chromosome is sufficient to inhibit activation of anaphase-promoting complex (triggers progression from metaphase to anaphase by signaling the degradation of cyclin B and cohesins)= repressed so kinetochore microtubules are attached (all have to be attached in order to proceed)
What is apoptosis?
describes cell death is response to DNA damage, cells have inner leaflet phospholipids that get exposed to phagocytic macrophages
• chromosome condensation
• cleavage chromosomal DNA
• fragmentation of nucleus and entire cell
What is ced-1?
mutant not able to get rid of dead cells which is evident programmed cell death occurs
What is ced-3?
ced-1 mutated and corpses not occurred (missing a gene essential for cell death); causes cell death
What is ced-4?
What is ced-9?
inhibts ced-4 (anti-apoptotic)
What are caspases?
proteases that chew up other proteins and are the executioners of cell death
What are effector caspases?
proteases that causes cell to die (ced-3); degrades inhibitor of DNAse, degrades nuclear lamina, degrades actin etc
What are initiator caspases?
activting the effector caspase by cleaving it
What is Apaf-1?
human homolog to ced-4 which activates caspase-9 with the help of cytochrome C
What is the order of caspases?
Apoptosome: Apaf-1 + Cytochrome C (from Mitochondria) Caspase-9 Caspase-3 (inactive) Caspase-3 (active)
What is bcl-2?
functional human homolog of ced-9 and is a type of cancer which connects cell death to cancer
What happens if there is a mutation of bcl-2?
causes cancer and would be gain of function meaning too much of the protein is expressed = oncogene
If more antiapoptotic proteins in cell, then the cell is going to survive; if more pro-apoptotic protein then will trigger cell death
How can mitochondrial damage signal apoptosis?
Multidomain proapoptotic proteins punch holes in the mitochondria which causes the release of Cytochrome C which activates Caspase-9
• Punches holes in membrane which activates Cytochrome C which then activates Caspase-9
Single domain interacts with anti-apoptotic protein and displaces it
What does p53 do to mediate DNA damage-induced apoptosis?
p53 initiates, in response to DNA damage, stops cell cycle (allowing time for DNA repair) and starts apoptosis process (which causes production of single domain apoptosis proteins. Both lead to cellular and genetic stability.
ATM p53single domain proapoptotic multi-domain proapoptotic antiapoptotic Cytochrome C Apaf-1 Caspase-9 Caspase-3
What does the Akt pathway do?
promotes cell survival by blocking the proapoptotic proteins Bad and Bim
What is Bad?
proapoptotic protein; Akt blocks the production of Bad which inhibits cell death
What is Bim?
What does PI 3-kinase do?
blocks cell death when it is not regulated and promotes survival when combined with Akt
What does tumor necrosis factor signaling do?
induces apoptosis in cancer and virus-infected cells
What does TNF do?
directly activates caspase which initiates cell death
What is a stem cell?
undifferentiated to some extent and has the ability to divide, replaces itself, and one daughter cell goes on and differentiates (goes into G0, continue to divide, can induce from G0 to ability to divide).
What are fibroblasts responsible for?
enter G0 stage of the cell cycle and excrete collagen, ability for wound closure and are fully differentiated (can divide under PDGF which repairs cuts and other wounds).
What are endothelial cells differentiated and do they retain the ability to divide?
cells that line blood vessels are another type of fully differentiated cell that remains capable of proliferation (VEGF stimulates these again to leave G0 and go into G1).
What are totipotent stem cells?
can become anything and is unrestricted in differentiation, see them at earliest stages of embryonic development
What are pluripotent stem cells?
found in blastocyst (inner mass cells), can become anything accept for placenta, can produce heart, brain, etc
What are multipotent stem cells?
can renew itself and form many different things, not as restricted, find in adults
What are oligopotent stem cells?
can differentiate into a few different things, can replenish itself as it divides, find them in adults
What are unipotent stem cells?
Cell that can produce only one cell type
What is the role of stem cell differentiation in the renewal of epithelial tissue?
unipotent, stem cell can also become oligopotent
What is the role of stem cell differentiation in the renewal of skin?
unipotent and is rapidly dividing
How do stem cells in muscle play a key role in the repair of damaged tissue?
stem cells represent population of cells that are differentiated and are present in most adult tissues and can divide to produce one daughter cell that remains a stem cell and one that divides and differentiate
How can adult stem cells be used therapeutically to replace blood cells or treat skin injuries?
Hematopoietic stem cells differentiate cell populations (multipotent); producing a lymphoid cell, from hematopoietic stem cell, becomes B or T lymphocyte
can use bone marrow transplants
What is autologous?
using own genetic material derived skin or other parts of body to be used for grafts to not be rejected by body
What are embryonic stem cells and what are some reasons that they are cultured?
First cultured form mouse embryos in 1981, Embryonic stem cells can be directed to differentiate along specific pathways by the addition of appropriate growth factors to the culture medium
Can be directed to become anything in vitro
Culturing cells, providing them with removal of LIF, then differentiation happens
What is somatic cell nuclear transfer?
method by which cloned embryos can be produced using differentiated adult cells
Can take a somatic cell nucleus and introduce nucleus into egg forming an embryo which will make it the same composition as taking from nucleus
What is the theoretical process of therapeutic cloning?
a nucleus from an adult human cell could be transferred to an enucleated egg, which would then be used to produce stem cells in culture
Combined with gene transfer has been demonstrated in mice by correction of inherited immunodeficiency (barrier with humans is unethical)
What are induced ploripotent stem cells?
adult cells that are reprogrammed by four transcription factors to resemble embryonic stem cells, autologous and didn't require an embryo
What does cdk2/CyclinA do?
Goes S phase to G2 phase
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