cell growth and division Flashcards
what cells in the body don’t undergo cell division
- gametes
- red blood cells
- most neurons
- some muscle cells
somatic cells
general term for a body cell and all human cells except for the cells that produce eggs and sperm (germ cells)
- contain 2 copies of each of their chromosomes (one copy received from each parent)
homologous
- pair of chromosomes is the two copies of single chromosome found in each somatic cell
diploid organism
- humans are!
- have 23 homologous pairs of chromosomes in each of the somatic cells
diploidy
condition of having pairs of chromosomes
Interphase
- period of cell cycle during which the cell is not dividing
- majority of cells are in interphase
mitosis
division of genetic material during which cell nucleus breaks down and two new fully functional nuclei are formed
cytokinesis
divides the cytoplasm into two distinctive cells
what are the two general phases of the cell cycle
- interphase
- mitosis and cytokinesis
what are the phases in interphase?
- g1 phase: growth phase (spend most of time here)
- s phase: synthesis phase, cell replicates its dna, dna doubles
- g2 phase: cell continues to grow and makes necessary preparations for mitosis
g0 phase: resting phase of cell cycle, cells temporarily stop dividing and are resting, and those who have permenantly stopped dividing (nerve cells)
what are each copies of the chromosome called
sister chromatid
centromere
structure that attaches one sister chromatid to another
- 46 chromosomes (92 chromatids)
Mitotic Phase - what are the 2 parts?
- complete mitosis (contents of nucleus are equally pulled apart and distributed)
- cytokinesis (divides cytoplasm and cell body into 2 new cells)
what are the 4 major stages of mitosis?
prophase, metaphase, anaphase, and telophase
prophase
- first phase of mitosis
-loosely pascked chromatin coils and condenses into visible chromosomes - chromosomes become visible with identical partner attached
- forms x shape of sister chromatids
- nucleolus disappears early in this phase
- nuclear envelope also disintegrates
- centrosomes begin to move apart during prophase
- centrosomes migrate to different sides of the cell
- microtubules extend from each ends like fingers
centrosome
- a pair of centrioles together
- cell has 2 centrosomes side to side
mitotic spindle
structure composed of centrosomes and their emerging microtubules
mitotic phase
- cell typically takes between 1-2 hrs
- ## cell undergoes 2 major processes: mitosis and cytokinesis
mitosis
- the contents of the nucleus are equitably pulled apart and distributed between its two halves
- four major stages after interphase: prophase, metaphase, anaphase, telophase
cytokinesis
divides the cytoplasm and cell body into two new cells
describe prophase
- prophase
- chromosomes condense and become visible w a partner attached (forms x-shaped sister chromatids)
- spindle fibers emerge from centrosomes
- nuclear envelope breaks down
- centrosomes move toward opposite poles
- becomes an important structure that contains the site for microtubules growth.
- prometaphse
- chromosomes continue to condense
- kinetochores appear at the centrosomes
-mitotic spindle microtubules attach to kinetochores
- metaphase
- chromosomes are lined up at metaphase plate
- each sister chromatid is attached to a spindle fiber originating from opposite poles
- anaphase
- centrosomes split in two and forms individual chromosomes
- sister chromatids (now called chromosomes) are pulled towards opposite poles by kinetochores as microtubules shorten
- certain spindle fibers begin to elongate the cell
- each end of cell receivves one parter from each pair os sister chromatids
- telophase
- chromosomes arrive at oppostive poles and begin to decondense
- nulear envelope material surrounds each set of chromosomes
- new nucleoli from around nuclei
- the mitotic spindle breaks down
- spindle fibers continue to push poles apart
- cell begins to split in half
- cytokinesis
- animal cells: a cleavage furrow separates the daughter cells
- plant cells: a cell plate the precursor to a new cell wall, separates the daughter cells
Centrosome
- a pair of centrioles together
-each cell contains 2 side-by-side - ## move apart during prophase
centrioles
- cellular structures that serve as origin points from which microtubules extend
mitotic spindle
- a structure composed of centrosomes and their emerging microtubules
kinetochore
protein structure on the centromere that is the point of attachment between the mitotic spindle and sister chromatids
metaphase plate
the name for the plane through the center of the spindle on which the sister chromatids are posisitoned
cleavage furrow
- contractile band made up of microfilaments that form around midline of cell during cytokinesis
- microfilaments made up of actin
- squeezes the two until they seperate
Cyclin
one of primary classes of cell control molecules
cyclin-dependent kinase (CDK)
one group of molecules that work together with cyclins to determine progression past cell checkpoints
