The Cell Cycle- L10

Cell theory

all cellular life is made of one or more cells

basic organizational and functional units of all organisms

all cells come from other cells

Goal of cell division

unicellular organisms: reproductions

multicellular organisms: growth & development, tissue repair/renewal

During cell division

all parts of the cell divided into new cells

one main function of cell division: distribute genetic material into daughter cells

Genome

a cells total genetic material

Chromosome

molecule of DNA in a cel

Chromatin

DNA/protein complex in dispersed state

• thread or fiber-like

DNA in this state when not actively dividing

Ploidy

number of sets of chromosomes in the nucleus of a cell

Haploid (n)

having one complete set of chromosomes

• gametes are haploid

Diploid (2n)

having 2 complete sets of chromosomes

2 of the same chromosome- homologous chromosomes or homologous pair

• somatic cells in human are diploid

Interphase

longest time period

cell is highly active (lives its normal life before division)

growth, synthesis, metabolic activity

DNA in chromatin

• G1, S, G2

G1 (Gap 1)

growth and normal development and function

• accumulating different parts required for replication

S phase

S= synthesis

chromosomes duplicated and chromosomal protein synthesis

• does not change ploidy

2 sister chromatids

• identical copies, connected by centromere

  • DNA still in chromatin at this stage

G2 (Gap 2)

usually shorter than G1 or S

DNA is still in chromatin

high metabolic activities, preparations for mitosis

• makes sure all DNA is copied properly

M Phase

Mitosis & Cytokinesis

Mitosis (Phases)

1. Prophase

2. Metaphase

3. Anaphase

4. Telopshase

Prophase

chromosomes condense

nucleus breaks down

mitotic spindle forms

• absence of nuclear envelope

Mitotic spindle

fibers within cell oriented from pole to pole of the cell

• guide chromosome movement during mitosis

Metaphase

chromosomes align at metaphase plate

• imaginary line chromosomes align at

Anaphase

sister chromatics separate & move to opposite poles

• pulled by kinetochores- proteins attached to centromeres

after seperation each chromatid is considered a chromosome

Telophase

opposite of prophase

• chromosomes start to de-condense

• nuclear envelope reforms

• new nuclei identical to parents nucleus

Cytokinesis

Cytoplasmic division —> 2 cells, with with 2 nucleus

does not simultaneously happen with telophase

some cells undergo cytokinesis, sometimes overlaps with telophase

• Goal: create 2 identical daughter cells

Cytokinesis in animals

Cleavage furrow

contracts undtil parent cell pinched

Cytokinesis in plant cells

Cell plate

new membrane at location of metaphase plate

• fuses with plasma membrane, divides daughter cells