| Question | Answer |
| what distinguishes living things from nonliving matter | the ability of organisms to produce more of their own kind |
| cell division | the continuity of life is based on the reproduction of cells |
| in unicellular organism | division of one cell reproduces the entire organism |
| multicellular organisms depend on cell division for | development from a fertilized cell, growth, and repair |
| cell division is an | integral part of the cell cycle |
| cell cycle | the life of a cell from formation to its own division |
| cell division results in | daughter cells with identical genetic information, dna. with the exception of meiosis |
| meiosis | special type of divison that can produce sperm and egg cells |
| genome | all the dna in a cell |
| genome can consist of | a single dna molecule (prokaryotic cells) or a number of DNA molecules (eukaryotic cells) |
| chromosomes | packaged dna molecules |
| chromatin | complex of dna and protein that condenses during cell division in eukaryotic chromosomes |
| eukaryotic species have a | characteristic number of chromosomes in each cell nucleus |
| somatic cells | nonreproductive cells which have 2 sets of chromosomes |
| gametes | reproductive cells: sperm and eggs which have half as many chromosomes as somatic cells |
| in preparation for cell division | dna is replicated and chromosomes condense |
| each duplicated chromomses have | 2 sister chromatids (joined copies of original chromosome) which separate during cell division |
| centromere | the narrow waist of the duplicated chromosome where two chromatids are most closely attached |
| the 2 sister chromatids during cell division | separate and move into two nuclei, once separate the chromatids are called chromosomes |
| eukaryotic cell division consist of | mitosis and cytokinesis |
| mitosis | the division of the gentic material in the nucleus |
| cytokinesis | the division of the cytoplasm |
| gametes are produced by | meiosis which yields nonidentical daughter cells that have only one set of chromosmes and half as many as the parent cell |
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| cell cycle consists of | mitotic phase (mitosis and cytokinesis) and interphase (cell growth and copying of chromosomes in preparation for cell division) |
| interphase | 90% of the cycle |
| subphases of interphase | G1 phase (first gap) S phase (synthesis) and G2 phase second gap |
| cell in subphases of interphase | grow in all three phases but chromsomes are duplicated only during the S phase |
| 5 phases of mitosis | prophase, prometaphase, metaphase, anaphase, telophse with the latter stages being overlapped by cytokinesis |
| mitotic spindle | structure made of microtubules that controls chromosome movement during mitosis |
| centrosome | microtubule organizing center, where assembly of spindle microtubules begins |
| during interphase centrosomes | replicat e, forming two centrosomes that migrate to opposite ends of the cell during prophase and prometaphase |
| aster | a radial array of short microtubules which extends from each centrosomes |
| the mitotic spindle includes | centrosomes, the spindle microtubules and the asters |
| during prometaphase | some spindle microtubules attach to the kinetochores of chromoes and begin to move the chromosmes |
| kinetochores | protein complexes associated with centromeres |
| at metaphase | the chromosoems are all lined up at the metaphase plate |
| metaphase plate | imaginary structure at the midway point between the spindles two poles |
| in anaphase | sister chromatids separate and move along the kinetochore microtubules toward opposite ends of the cell, the microtubules shorten by depolymerizing at the kinethochore ends |
| nonkinetochore microtubules in anaphase | from opposite poles overlap and push against each other elongating the cell |
| telophase | genetically identical daughter nuclei fom at opposite ends of the cell |
| cytokinesis begins | during anaphase or telophase and the spindle eventually disassembles |
| cytokinesis occurs by | a process known as cleavage forming a cleavage furrow |
| in plants, | cell plate froms during cytokinesis |
| binary fision | a cell division which prokaryotes (bacteria and acrhaea) reproduce by |
| during binary fission | the chromosomes replicates ( beginning at the origin of replication) and the two daughter chromsomes actively move apart, the plasma membrane piches inward dividing the cell into two |
| because prokaryotes evolved before eukaryotes | mitosis probably evolved from binary fission |
| certain protists exhibit | types of cell division that seem intermediate between binary fission and mitosis |
| frequency of cell divison varies with | the type of cell which result from regulation at the molecular level |
| cancer cells manage | to espcape the usual controls on the cell cycle |
| the cell cycle is driven by | specific chemical signals present in the cytoplasm, evidence comes from experiments of cultured mammalian cells at different phases of the cell cycle were fused to form a single cell with 2 nuclei |
| cell cycle control system | similar to a clock, direct sequential events of the cell cycle |
| cell cycle control system is regulated by | both internal and external controls |
| the clock has | specific checkpoints wehere the cell cycle stops until a go ahead signal is received |
| G1 check point | the most important, if cell revieves go ahead signal here, it completes the S and G2 and M phases and divide |
| if cell does not receive go ahead signal | it will exit the cycle switching into a nondividing state called the G0 phase |
| types of regulatory proteins invoved in cell cycle control | cyclins and cyclin dependent kinases (Cdks) |
| Cdks | acitivty fulucates during the cell cycle because it is controlled by cylcins so named because their concentrations vary with the cell cycle |
| Maturation promoting factor (MPF) | a cyclin Cdk complex that triggers a cells passage past te G2 checkpoint into M phase |
| example of an interal signal | kinetochores not attached to spindle microtubules send a molecular signal that delays anaphase |
| external signals are | growth factors, proteins released by cetain cells that stimulate other cells to divide |
| ex of growth factor | platelet derived growth factor which stimulates the division of human fibroblst cells in culture |
| ex of external signals | density dependent inhibitions wher crowded cells stop dividing |
| anchorage dependence | in animal cells, where they must be attached to a substratum in order to divide |
| cancer cells do not | exhbit desity dependent inhibition nor anchorage dependence |
| cancer cells do not need | growth factors to grow and divide, they make their own growth factor, convey its singal w/o presence of it, and may have an absnormal cell cycle control system |
| transformation | when a normal cell is convereted to a cancerous cell |
| cancer cells that are not eliminated by | the immune system from tumors, masses of abnormal cells within otherwise normal tissue |
| benign tumor | a lump where abnormal cells remain only at the original site |
| malignant tumors | invade surrounding tissues and can metastasize |
| metastasize | exporting cancer cells to other parts of the body where they may form additional tumors |
| advances in understanding cell cycle and cell signaling have led to | advances in cancer treatment |
