Alberts, Ch 17 - Cell Cycle Flashcards
Anaphase A
Stage of mitosis, initial poleward movement of the chromosomes during which kinetocore microtubules shorten
Anaphase B
Stage of mitosis when spindle poles separate and daughter chromosomes move toward opposite poles
Anaphase-promoting complex (APC/C)
Ubiquitin ligase that catalyzes ubiquitylation and destruction of securin and M- and S-cyclins initiating separation of sister chromatids in metaphase-to-anaphase transition during mitosis, also known as cyclosome
Astral microtubule
In the mitotic spindle any of the microtubules radiating from the aster which are not attached to kinetochore of a chromosome
ATM
Ataxia telangiectasia mutated protein, protein kinase activated by double-strand DNA breaks, if breaks not repaired ATM initiates signal cascade that culminates in cell cycle arrest
ATR
Ataxia telangiectasia and Rad3 related protein, protein kinase activated by DNA damage, if damage remains unrepaired helps initiate signal cascade that culminates in cell cycle arrest
Bi-orientation
Attachment of sister chromatids to opposite poles of mitotic spindle so that they move to opposite ends of the cell when they separate in anaphase
Bivalent
Four-chromatin structure formed during meiosis consisting of a duplicated chromosome tightly paired with its homologous duplicated chromosome
Cdc20
Activating subunit of anaphase-promoting complex
Cdc25
Protein phosphatase that dephosphorylates Cdks and increases their activity
Cdc6
Protein essential in preparation of DNA for replication, with Cdt1 binds to origin recognition complex on chromosomal DNA and helps load the Mcm proteins onto the complex to form prereplicative complex
Cdh1
Activating subunit of anaphase-promoting complex
Cdk inhibitor protein (CKI)
Protein that binds to and inhibits cyclin-Cdk complexes, involved in control of G1 and S phases
Cdk-activating kinase (CAK)
Protein kinase that phosphorylates Cdks in cyclin-Cdk complexes activating Cdk
Cdt1
Protein essential in preparation of DNA for replication, with Cdc6 binds to origin recognition complexes on chromosomes and helps load the Mcm proteins on to the complex forming prereplicative complex
Cell cycle
Reproductive cycle of a cell, orderly sequence of events by which cell duplicates its chromosomes and other cell contents and divides into two
Cell-cycle control system
Network of regulatory proteins that governs progression of eukaryotic cell through cell cycle
Centrosome
Centrally located organelle of animal cells that is primary microtubule-organizing center (MTOC) and acts as the spindle pole during mitosis, contains a pair of centrioles
Chiasma (plu. Chiasmata)
X-shaped connection visible between paired homologous chromosomes during meiosis, represents a site of chromosomal crossing-over, form of genetic recombination
Condensin
Complex of proteins involved in chromosome condensation prior to mitosis, target for M-Cdk
Contractile ring
Ring containing actin and myosin that forms under the surface of animal cells undergoing cell division, contracts to pinch the two daughter cells apart
Cyclin
Protein that periodically rises and falls in concentration in step with eukarotic cell cycle, activates protein kinases (Cdks) and helps control progression from one stage of cell cycle to the next
Cyclin-dependent kinase (Cdk)
Protein kinase that has to be complexed with cyclin protein in order to act, different cyclin-Cdk complexes trigger different steps in cell-division cycle by phosphorylating specific target proteins
Cyclin-Cdk complex
Protein complex formed periodically during eukaryotic cell cycle as level of particular cyclin increases, Cdk then becomes partially activated
Cytokinesis
Division of cytoplasm of cell into two, distinct from associated division of its nucleus, part of M phase
E2F protein
Transcription regulatory protein that switches on many genes that encode proteins required for entry into S phase
G0
State of withdrawal from eukaryotic cell-division cycle by entry into quiescent digression from G1 phase, common, sometimes permanent state for differentiated cells
G1 phase
Gap 1 phase of eukaryotic cell cycle, between end of mitosis and start of DNA synthesis
G1-Cdk
Cyclin-Cdk complex formed in vertebrate cell by G1-cyclin and corresponding Cdk
G1-cyclin
Cyclin present in G1 phase, forms complexes with Cdks that help govern activity of G1/S-cyclins
G1/S-Cdk
Cyclin-Cdk complex formedby G1/S-cyclin and corresponding Cdk
G1/S-cyclin
Cyclin that activates Cdks in late G1 and helps trigger progression through Start resulting in commitment to cell-cycle entry, levels fall at start of S phase
G2 phase
Gap 2 phase, between end of DNA synthesis and beginning of mitosis
G2/M transition
Point in eukaryotic cell cycle at which cell checks for completion of DNA replication before triggering early mitotic events that lead to chromosome alignment on the spindle
Geminin
Protein that prevents formation of new prereplicative complexes during S phase and mitosis ensuring that chromosomes are replicated only once in each cell cycle
Growth factor
Extracellular signal protein that can stimulate a cell to grow, often have other functions as well such as stimulating cell to survive or proliferate, examples epidermal growth factor (EGF) and platelet-derived growth factor (PDGF)
Interphase
Long period of cell cycle between one mitosis and the next, includes G1, S and G2 phases
Interpolar microtubule
In mitotic or meiotic spindle, microtubule interdigitating at the equator with microtubules emanating from the other pole
Kinetochore
Large protein complex that connects the centromere to microtubules of mitotic spindle
Kinetochore microtubule
In mitotic or meiotic spindle, a microtubule that connects the spindle pole to kinetochore of chromosome
M-Cdk
Cyclin-Cdk complex formed by M-cyclin and corresponding Cdk
M-cyclin
Cyclin found in all eukaryotic cells that promotes events of mitosis
Meiosis I
First chromosome segregation following meiotic chromosome duplication, segregates homologs
Meiosis II
Second chromosome segregation following meiotic chromosome duplication, segregates sister chromatids of each homolog
Metaphase-to-anaphase transition
Transition preceding sister chromatid seperation at anaphase, if cell not ready to proceed to anaphase cell cycle halted here
Mitogen
Extracellular signal molecule that stimulates cells to proliferate
Mitotic spindle
Bipolar array of microtubules and associated molecules that forms during mitosis and serves to move duplicated chromosomes apart
Microtubule flux
Movement of individual tubulin molecules in the microtubules of the spindle toward the poles by loss of tubulin at their minus ends, helps generate poleward movement of sister chromatids after they separate in anaphase
Myc
Transcription regulatory protein that is activated when a cell is stimulated to grow and divide by extracellular signals, activated transcription of many genes, including those that stimulate cell growth
Nondisjunction
Event occuring occasionally during meiosis in which a pair of homologous chromosomes fails to separate so that resulting germ cell has either too many or too few chromosomes
Origin recognition complex (ORC)
Large protein complex that is bound to DNA at origins of replication in eukaryotic chromosomes throughout the cell cycle
p53
Transcription regulatory protein that is activated by damage to DNA and is involved in blocking further progression through cell cycle, also a tumor suppressor gene that is mutated in about half of human cancers (the gene encoding the protein)
Pairing
In meiosis lining up of the two homologous chromosomes along their length
Prereplicative complex (preRC)
Multiprotein complex that is assembled at origins of replication during late mitosis and early G1 phases, prerequisite to license assembly ofpreinitiation complex and subsequent initiation of DNA replication
Ras
Monomeric GTPase of Ras superfamily that helps to relay signals from cell-surface receptor tyrosine kinase receptors to nucleus in response to signals that stimulate cell division, also family of proto-oncogenes that frequently mutate in cancer (code for the protein)
Replicative cell senscence
Phenomenon observed in primary cell cultures in which cell proliferation slows down and finally irreversibly halts
Restriction point
Important transition at end of G1, commits cell to enter S phase
Retinoblastoma (Rb) protein
Tumor suppressor protein involved in regulation of cell division, mutated in cancer retinoblastoma and other tumors, normal activity is to regulates cell cycle by binding to and inhibiting E2F proteins blocking progression to DNA replication and cell division
S-Cdk
Cyclin-Cdk complex formed by S-cyclin and corresponding Cdk
SCF
Family of ubiquitin ligases formed as complex of several different proteins, one involved in regulating cell cycle, directing destruction of inhibitors of S-Cdks in late G1 and promoting activation of S-Cdks and DNA replication
S-cyclin
Member of class of cyclins that accumulate during late G1 and bind Cdks soon after progression through Start, help stimulate DNA replication and chromosome duplication, levels remain high until late mitosis after which destroyed
Separase
Protease that cleaves cohesin protein linkages that hold sister chromatids together, acts at anaphase enabling chromatid separation and segregation
Sister chromatids
Tightly linked pair of chromosomes that arise from chromosome duplication during S phase, they separate during M phase and segregateinto different daughter cells
Spindle assembly checkpoint
Regulatory system that operates during mitosis to ensure that all chromosomes are properly attached to the spindle before sister chromatid separation starts
Start
Important transition at end of G1 in eukaryotic cell cycle, passage through commits cell to enter S phase
Synaptonemal complex
Structure that holds paired homologous chromosomes tightly together in pachytene of prophase I in meiosis and promotes final steps of crossing over
Syncytium
Mass of cytoplasm containing many nuclei enclosed by single plasma membrane, typically result of cell fusion or series of incomplete division cycles in which nuclei divide but cell does not
Telomerase
Enzyme that elongates telomere sequences in DNA
Telophase
Final stage of mitosis in which two sets of separated chromosomes decondense and become enclsoed by nuclear envelope
Wee1
Protein kinase that inhibits Cdk activity by phosphorylating amino acids in Cdk active site, important in regulating entry into M phase
Prophase
First stage of mitosis during which replicated chromosomes condense, mitotic spindle assembles
Prometaphase
Second stage of mitosis, nuclear envelope breaks down, enables spindle attachment to chromosomes
Metaphase
Third stage of mitosis, chromosomes aligned at equator of spindle, kinetochore microtubules attach sister chromatids to opposite poles of spindle
Anaphase
Stage of mitosis during which sister chromatids separate and move away from each other, in meiosis chromosome homolog pairs separate (I) and sister chromatids separate (II)
