Cell Cycle

Chromosomes Carry genetic information passed from one generation to the next. Made of DNA Human body cells have 46 chromosomes

Chromatids – identical parts of a chromosome “sister” chromatids carry same info as chromosome Centromere – area where chromatids are attached Each new cell gets an exact copy of the original DNA so that each cell can function properly. Sister chromatids Centromere

Why do cells divide? Growth Replace damaged or old cells Produce new individuals in single celled organisms

Cell Cycle (phases in the life of a cell) During the cell cycle: Growth Preparing to divide Division – two daughter cells are formed Start cycle over QUESTION: What is the goal?

Goal = To Make two Identical Daughter Cells Parent Cell

The cell cycle consists of four phases: G1 (First Gap Phase) S Phase (Synthesis) G2 (Second Gap Phase) M Phase (Mitosis)

G1 Phase: (Gap phase 1) S phase (synthesis) Cell grows synthesizes new proteins and organelles S phase (synthesis) chromosomes are replicated DNA synthesis takes place

The G1, S, & G2 together are Interphase G2 Phase (Gap Phase 2) Final preparation for cell division Makes organelles needed for mitosis The G1, S, & G2 together are Interphase M phase—Mitosis and Cytokinesis - cell division - division of the cytoplasm

Cell Cycle Interphase: Cell Division G0 G1, S, G2 Intermission from division; used to be called the resting stage, however, the cell is actually very active as it prepares to divide. Cell Division Mitosis – nucleus divides Cytokinesis – cytoplasm divides G0 the cell stops dividing and specializes (gets a job)

I – P – M – A - T Mitosis Splitting of the nucleus *Interphase (cell prepares to divide: G1, S, G2) Prophase Metaphase Anaphase Telophase I – P – M – A - T

Remember: Goal = To Make two Identical Daughter Cells Parent Cell

Interphase Cell prepares to divide G1 (First Growth) S (Synthesis of DNA) G2 (Second Growth)

Prophase 1st and longest Centrioles move to the poles Spindle forming 1st and longest Centrioles move to the poles Organize the spindle Chromosomes condense Nuclear envelope breaks down Centromere Chromosomes (paired chromatids) Copyright Pearson Prentice Hall

Metaphase Chromosomes line up across the middle of the cell Centriole Chromosomes line up across the middle of the cell Spindles attach to centromeres Spindle Copyright Pearson Prentice Hall

Anaphase Chromatids separate Are pulled to the poles Individual chromosomes Chromatids separate Are pulled to the poles Copyright Pearson Prentice Hall

Telophase Opposite of Prophase Chromosomes lose shape Nuclear envelope reforms Spindles break down Copyright Pearson Prentice Hall

Cytokinesis Splitting of the cytoplasm Occurs at the same time as Telophase Animal cell – pinches in (cleavage furrow)

Plant cell – a cell plate is formed NO centrioles

Cell Cycle Regulation Pg 250 Ch. 10-3

Controls on Cell Division Experiments show that normal cells will reproduce until they come into contact with other cells. When cells come into contact with other cells, they respond by not growing.

The controls of the cell cycle can be turned on and off

Cyclins: Proteins that regulate the timing of the cell cycle Amount rises and falls with the cell cycle

Internal Regulators proteins that respond to events inside the cell Act as checkpoints

External Regulators proteins that respond to events outside the cell Cause the cell cycle to speed up or slow down

Cancer Disorder in which the body’s cell lose the ability to control growth Do not respond to cyclins Divide uncontrollably – form tumors

Problem Solving Activity Imagine that you are developing a drug that will inhibit the growth of cancer cells. Use you knowledge of the cell cycle to describe how your drug would target and prevent the multiplication of cancer cells.