10.2 The Process of Cell Division

Preparing for division.. One cell will divide into two new, identical cells Parent cell – original Daughter cell – new cells

Before division, DNA must be copied each new cell gets an identical copy of the parent cell’s DNA

Chromosomes. Condensed packages of chromatin (DNA and proteins) Prokaryotes – Contain a single circular chromosome

Eukaryotes usually contain several chromosomes! Fruit fly – 8 Carrot – 18 Human – 46 Chicken – 78

Formation of chromosomes DNA wraps around proteins called histones, and forms structure called nucleosomes

Nucleosomes condense and twist to form coils.

Coils twist and tighten further to form super coils.

Supercoils fold up to form a single chromosome.

Chromosomes formed during cell division contain two identical pieces Each piece is called a sister chromatid Held together at center by the centromere

Cell cycle and division of Prokaryotes.. Cycle involves periods of growth, DNA replication, and division Divides (asexually reproduces) by process call Binary Fission DNA is copied  Cell pinches at center  Cell splits in half

Cell Cycle & Division in Eukaryotes.. Overview: Involves two primary phases Interphase Interphase is separated into 3 stages  G1 – Gap 1  S - Synthesis  G2 – Gap 2

2. M Phase M Phase is separated into 2 stages:  Mitosis  Cytokinesis

Interphase Most of cell’s life is spent in interphase Period between division in which cell performs normal functions and prepares to divide

G1 - Cell growth  Cell grows to normal size  Produce new proteins and organelles S – Synthesis of DNA  DNA (chromosomes) is copied to make two identical sets of DNA G2- Prep for mitosis  Structures needed for mitosis are produced

M Phase Very short Mitosis – Division of the nucleus  Nucleus is broken down  Chromosomes are separated (1 set for each cell)

Cytokinesis – Division of the Cytoplasm  Organelles are divided

Mitosis Prophase Metaphase Anaphase Telophase PMAT

Prophase DNA condenses into chromosomes Nucleus begins to break down Centrioles begin to separate and begin producing spindles Spindles – microtubules that separate the chromosomes during mitosis

Metaphase Spindles attach to chromosomes Chromosomes are pulled towards center of cell Line up at metaphase plate

Anaphase Spindle fibers pull sister chromatids apart Each sister chromatid from each chromosome moves to opposite end of the cell Cell begins to elongate

Telophase Chromatids (single chromosomes at this point) reach ends of cell Spindle fibers break apart Nucleus begins to reform

CYTOKENISIS Cell membrane pinches inward at center Each side of cell separates when membrane meets at center Cell cycle will continue for each new cell at G1

Quiz TIME!!!!