Cell Cycle Flashcards
what is a genome?
all the genetic info contained in the chromosomes of an organism
what are chromosomes and chromatin?
chromosomes - packaged DNA
chromatin - “unwound” DNA that condenses itself during cell division
what are diploid and haploid cells?
diploid - a complete set of 2 sets of chromosomes (2n = 46)
haploid - a half set of chromosomes (1n = 23), the gametes (sex cells) of both sexes (23 + 23 = 46)
what are sister chromatids and a centromere?
sister chromatids - identical copies of one chromosome, held together at the centromere
what are the three types of cell division?
mitosis - dividing of nucleus’ genetic code
cytokinesis - division of the cell’s cytoplasm
meiosis - diving of gamete cells
what are the 3 big “stages” of cell division?
- interphase
- mitosis (also called M phase)
- cytokinesis
what are the 3 steps of interphase?
G1 - cells get bigger and make more proteins + organelles needed to make 2 cells
S - cell makes a duplicate copy of its DNA in the nucleus
G2 - cell makes more proteins/organelles, and begins to move its contents around in preparation to split
what are the five stages of mitosis?
- prophase
- pro-metaphase
- metaphase
- anaphase
- telophase
what occurs in a cell during prophase?
-mitotic spindles begin to form
-chromatin begins to condense into chromosomes
-nucleolus (where ribosomes are made) disappears
what occurs in a cell during prometaphase?
-chromosomes become very compact and held together by centromeres
-nuclear envelope breaks down, releasing chromosomes into cell cytoplasm
-mitotic spindle grows more, some microtubules begin to “grab” some centromeres
what occurs in a cell during metaphase?
-chromosomes align at the “metaphase plate,” a plane where they all line up
-kinetochores of each chromosome should be attached to opposite spindles
what occurs in a cell during anaphase?
-microtubules attached to centromeres begin to pull apart the sister chromatids, forming 2 pairs of each chromosome
-microtubules not attached to centromeres will push the chromosomes away to their respective corners of the cell
what occurs in a cell during telophase and cytokinesis?
-mitotic spindle is broken down
-nucleolus and nuclear envelope begin to reform
-a “cleavage furrow” begins to form which “pinches” the cell in half, forming 2 new cells from one cell
what is the mitotic spindle?
-a bunch of microtubules that control chromosome movement, form during prophase and prometaphase
-arise from centrosomes in animal cells
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what are kinetochores?
a patch of motor proteins found at the centromere of each sister chromatid, each sister chromatid has one. these proteins bind to the mitotic spindles that pull them
what are kinetochore and non kinetochore microtubules?
-kinetochore microtubules are microtubules from the spindles that attach to the kinetochore of chromosomes and move them to the metaphase plate
-non kinetochore microtubules are microtubules that overlap and elongate the cell during anaphase
how is plant cell cytokinesis different from animal cell cytokinesis?
animal cells - cell gets pinched @ cleavage furrow, gets split in half
plant cells - golgi vesicles form in middle of cell and fuse together to form a new cell wall that separates two cells.
how does cell type dictate frequency of cell division?
-skin cells will continually divide as the body is always being microscopically “damaged” and sloughing off dead cells
-some cells can divide but only if they need to [eg , liver cells]
-some cells cannot divide, such as mature nerve and muscle cells
what is the “cell cycle”?
-a series of events that are maintained and directed by a cell cycle control system, a set of molecules that triggers and coordinates certain key events in the cycle, regulated @ checkpoints`
what are cell cycle checkpoints?
-points in the cell cycle where division is stopped until a go signal is received, can be an internal or external signal
where do the cell cycle checkpoints occur?
-end of G1 = go or no go signal
-end of G2
-during metaphase
what are cyclins and cyclin dependent kinases?
proteins that regulate cell cycle checkpoints
-Cdks are always present, but only activate when bound to with cyclin
-serve as go ahead signals for G1 and G2 checkpoints
what is MPF / maturation promoting factor?
-a cyclin-cdk complex that triggers a cell to pass from G2 into the M phase of cell division
-this factor is self regulating and degrades its cyclins in anaphase
what is the M phase checkpoint?
-occurs during metaphase
-controls start of anaphase, only goes ahead when all kinetochores are attached to kinetochore microtubules to ensure all cells have equal #s of chromosomes
what are external growth factors?
-proteins released by one cell that stimulate another to divide
-ex. platelet derived growth factor - stimulates cell division at a wound to clot / help heal
what is density dependent inhibtion?
-when cells touch each other, inhibiting signals are sent to both to stop excess cell growth
what is anchorage dependence?
-cells must be attached to a substratum layer in order to divide, stops excess / cancerous cell growth
