the cell life cycle

importance of cell division

* has ability to turn 1 fertilized cell into 30 trillion cells at maturity
* new cells are added to growing structures
* old/damaged cells get replaced

2 things mitotic cell division requires

* DNA replication: chromosomes in the nucleus must be exactly duplicated


* mitosis: distribution of duplicated chromosomes and division of the nucleus/cytoplasm to ensure that one exact copy of chromosomes ends up in each of the 2 daughter cells

cell cycle

series of changes a cell goes through from the time it is formed to the time it reproduces itself

2 major phases of the cell cycle

* mitosis: produces 2 somatic daughter cells each with 46 chromosomes
* meiosis: produces sex cells each with 23 chromosomes

G1 subphase

* lots of cell growth occurs
* cell must pass through a G1 restriction point

S subphase

* each of the 46 chromosome strands replicates, making sister chromatids (copied strands)

centromere

structure that holds the sister chromatids together

G2 subphase

* final preparation for mitosis
* enzymes and other proteins needed for division are synthesized

what happens to the centrosome by the end of interphase

centrosome completes replication, resulting in 2 centrosomes

prophase

* nuclear envelope membrane breaks down
* sister chromatids condense
* pair of centrosomes build mitotic spindle apparatus

mitotic spindle apparatus

network of protein rods

metaphase

* mitotic spindle apparatus attaches to the centromere of each sister chromatid pair
* mitotic spindle apparatus moves sister chromatids and lines them up along the metaphase plate

anaphase

* sister chromatids get separated by the mitotic spindle apparatus
* one chromosome from each pair moves to opposite sides of the cell

telophase

* nuclear envelope reforms around the centrosomes
* chromosomes decondense
* mitotic spindle apparatus breaks down but centrosome remains

cytokinesis

cytoplasm splits making 2 separate daughter cells, completing in the telophase