Ch 9,10,12,13 Flashcards
Cell division:
The continuity of life is based on the reproduction of cells.
Integral part of cell cycle.
Passing identical genetic material to cellular offspring is a crucial fxn.
Cell cycle:
The life of a cell from the time it is first formed during division of a parent cell until its own division into two daughter cells.
Genome:
A cell’s endowment of DNA, its genetic information.
Prokaryotic cells- have 1 single DNA molecule.
Eukaryotic cells- have a number of DNA molecules.
Chromosomes:
DNA molecules are packaged into structures called chromosomes.
Eukaryotic chromosomes have 1 very long linear DNA molecule associated with many proteins.
Associated proteins maintain the structure and help control the activities of genes.
Chromatin:
Together, the entire complex of DNA and proteins that is the building material of chromosomes.
Varies in its degree of condensation during the process of cell division.
Somatic cells:
All body cells except the reproductive cells.
Human somatic cells each contain 46 chromosomes, made up of 2 sets of 23, one from each parent.
Gametes:
Reproductive cells- sperm and eggs.
Have one set, or half as many chromosomes as somatic cells.
Sister chromatids:
Each duplicated chromosome has 2 sister chromatids.
Joined copies of the original chromosome.
Each contain identical an DNA molecule.
Initially attached along their lengths by protein complexes called cohesins, aka sister chromatid cohesion.
Centromere:
A region of the chromosomal DNA where the chromatid is attached most closely to its sister chromatid.
Mediated by proteins bound to the centromeric DNA, other bound proteins condense the DNA, giving it a narrow waist.
Mitosis:
The division of the genetic material in the nucleus, usually followed by cytokinesis.
Cytokinesis:
After mitosis, the division of the cytoplasm, well underway by late telophase.
One cell has become 2, each the genetic equivalent of the parent cell.
In animal cells, involves formation of cleavage furrow, which pinches cell in 2.
Mitotic (M) phase:
Includes both mitosis and cytokinesis, usually the shortest part of the cell cycle.
Alternates with interphase.
Interphase:
Often accounts for about 90% of the cycle.
Subphases:
- G1 phase (first gap)
- S phase (synthesis)
- G2 phase (second gap)
Cell grows in all 3 phases but the chromosomes are duplicated only during the S phase.
Meiosis:
A variation of cell division I which you produce gametes-sperm or egg.
Yields daughter cells with only one set of chromosomes, half as many as parent cells.
Reduces number of sets of chromosomes from 2 to 1 in gametes, counterbalancing the doubling that occurs at fertilization.
Mitosis is broken down into 5 stages:
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase/ cytokinesis
Mitotic spindle:
Many events of mitosis depend on this, which begins to form in the cytoplasm during prophase.
A structure made of microtubules that controls chromosome movement during mitosis.
G2 of Interphase:
Nuclear envelope encloses nucleus.
Nucleus has 1 or more nucleoli.
Single centrosome has duplicated, become 2. Each centrosome has 2 centrioles.
Chromosomes, duplicated during S phase, cannot be seen yet becuz they haven’t been condensed.
Centrosome:
In animal cells, starts the assembly of spindle microtubules.
A subcellular region containing material that functions throughout the cell cycle to organize the cell’s microtubules.
Microtubule organizing center.
Pair of centrioles are located at the center, not essential for cell division, also not present in plant cells.
Aster:
A radial array of short microtubules, extends from each chromosome.
Kinetochore:
A structure made up of proteins that have assembled on specific sections of DNA at each centromere.
Face opposite directions.
Each of the two sister chromatids of a duplicated chromosome has a kinetochore.
Metaphase plate:
Imaginary plate rather than an actual cellular structure.
Cleavage:
In animal cells, cytokinesis occurs by a process called cleavage.
First sign of cleavage is the appearance of a cleavage furrow.
Cleavage furrow:
A shallow groove in the cell surface near the old metaphase plate.
On cytoplasmic side the furrow is a contractile ring of actin microfilaments, which interact with myosin molecules, causing ring to contract.
The cleavage furrow deepens until parent cell is pinched in two, making 2 separate cells each with its own nucleus and own share of cytosol, organelles, and other subcellular structures.
Plant cells have no cleavage furrow.
Cell plate:
In plant cells, there is no cleavage furrow. Instead, in telophase, vesicles from Golgi apparatus move along microtubules to middle of cell where they coalesce, making the cell plate.
Cell wall materials carried on vesicles collect inside cell plate as it grows.
Cell plate enlarges until its surrounding membrane fuses with plasma membrane along perimeter of cell.
Making 2 daughter cells, each with own plasma membrane. New cell wall between.
Binary fission:
Division in half.
Prokaryotes can undergo type of reproduction in which cells grow to roughly double size, then divides to form 2 cells.
Also refers to Asexual reproduction of single- celled eukaryotes.
Origin of replication:
DNA of bacterial chromosome begins to replicate at this specific place on chromosome.
Produces 2 origins.
As chromosome continues to replicate, one origin moves rapidly toward the opposite end of cell.
Cell elongates, while chromosome is replicating.
After replication, bacterium is twice its size, plasma membrane pinches inward, making division into 2 daughter cells.
Cell cycle control system:
A cyclically operating set of molecules in the cell that both triggers and coordinates key event in the cell cycle.
Checkpoint:
A control point in the cell cycle where stop and go-ahead signals can regulate the cycle.
3 important checkpoints are found in the:
- G1 phase
- G2 phase
- M phase
Cyclin:
A protein that gets its name from it cyclically fluctuating concentration in the cell.
Cyclin- dependent kinases, or Cdks:
The activity of Cdk rises and falls with changes in the concentration of it cyclin partner.
MPF:
Stands for maturation- promoting factor, aka. M-phase-promoting factor.
The cyclin-Cdk complex that was discovered first (in frog eggs).
Peaks of MPF activity correspond to the peaks of cyclin concentration.
Triggers cell’s passage into the M phase past the G2 checkpoint.
G0 phase:
Nondividing state.
Most cell’s in the human body are in this phase. Mature nerve and muscle cells never divide.
Other cells (liver) can be called back from this phase to cell cycle by external cues, such as growth factors released during injury.
Growth factor:
A protein released by certain cells that stimulate other cells to divide.
Different cell types reaping specifically to different growth factors or combinations of growth factors.
Density-dependent inhibition:
Phenomenon in which crowded cells stop dividing.
If cells are removed, those bordering the open space begin dividing again and continue until space is filled.
Anchorage dependence:
Most animal cells exhibit this.
To divide, they must be attached to a substratum, such as inside a culture flask or the extracellular matrix of a tissue.
Signaled to the cell cycle control system via pathways involving plasma membrane proteins and element of the cytoskeleton linked to them.
Transformation:
Cells in culture that acquire the ability to divide indefinitely have undergone transformation.
The process that causes them to behave like cancer cells.
