12/3/13 Objective: What is the structure of a chromosome and what is its role in the cell cycle? Do Now: How many cells does mitosis produce?

Going from egg to baby…. the original fertilized egg has to divide… and divide… Getting from there to here…

For reproduction –asexual reproduction one-celled organisms For growth –from fertilized egg to multi-celled organism For repair & renewal –replace cells that die from normal wear & tear or from injury Why do cells divide? amoeba

Nucleus Cell Chromosomes Chromosomes are made of DNA!!

Thread-like structures found in the nucleus of cells that contain DNA

A combination of DNA and protein that make up a chromosome

The Cell Cycle Interphase 90% of cell cycle cell doing its “everyday job” makes proteins, etc (ex?) Prepares for duplication if triggered

Interphase can be divided into subphases –G 1 phase –S phase –G 2 phase

Interphase Divided into 3 phases: –G 1 = 1 st Gap (Growth) cell doing its “everyday job” cell grows –S = DNA Synthesis copies chromosomes –G 2 = 2 nd Gap (Growth) prepares for division cell grows (more) produces organelles, proteins, membranes G0G0 signal to divide

double- stranded mitotic human chromosomes

Mitotic Phase - Stage where the cell is actually dividing

Before you can share your notes, You have to make a copy

-Chromatin condenses -Can see sister chromatids -Nucleus disappears -Spindle fibers form Prophase

Protein fibers cross cell to form mitotic spindle –coordinates movement of chromosomes Microtubules: protein fibers that make up the spindle

-Sister Chromatids: two identical joined chromosomes

-Centromere: the region where the 2 chromatids are joined together

Metaphase Chromosomes align along middle of cell –metaphase plate meta = middle plane –spindle fibers coordinate movement

Anaphase Sister chromatids separate –move to opposite poles –pulled at centromeres

Telophase Chromosomes arrive at opposite poles –daughter nuclei form –nucleoli form –chromosomes disperse no longer visible under light microscope Spindle fibers disperse

12/16/11 Objective: Mitosis (cont’d) Do Now: 1.What is a sister chromatid? 2.What is the function of the spindle fibers?

Cytokinesis Animals Splitting of cytoplasm cleavage furrow forms (shallow groove near old metaphase plate) splits cell in two

Cytokinesis in Animals

Mitosis in whitefish blastula

Cytokinesis in Plants Plants –cell plate forms new cell wall

The Cell Cycle Control System The sequential events of the cell cycle –Are directed by a distinct cell cycle control system, which is similar to a clock Control system G 2 checkpoint M checkpoint G 1 checkpoint G1G1 S G2G2 M

The clock has specific checkpoints –Where the cell cycle stops until a go-ahead signal is received G 1 checkpoint G1G1 G1G1 G0G0 (a) If a cell receives a go-ahead signal at the G 1 checkpoint, the cell continues on in the cell cycle. (b) If a cell does not receive a go-ahead signal at the G 1 checkpoint, the cell exits the cell cycle and goes into G 0, a nondividing state. G0 phase: a non-dividing state

Fig G1G1 G0G0 G 1 checkpoint (a)Cell receives a go-ahead signal G1G1 (b) Cell does not receive a go-ahead signal

Cancer A disease caused by the disruption of the mechanism that normally controls the cell cycle Leads to uncontrolled cell divison

Tumor A mass produced by out-of-control cell reproduction

Types of Tumors Benign tumor: An abnormal mass of normal cells that can usually be removed by surgery Malignant tumor: masses of cells from the reproduction of cancer cells (can spread if not removed or killed)

Metastasis The spread of cancer beyond their original site

Prevention/Early Detection/Treatment

Getting Started

Interphase

Prophase

Metaphase

Drawing Metaphase

Anaphase

Telophase

Cytokinesis