5- Cell Cycle - PPT slides

 Scientists have

identified a repeating cycle of events in the life of a cell

 This cycle of events is

Every hour, about one billion (109) cells die and one billion cells are made in your body. Part of the cell cycle includes making new cells in a

 The cell cycle has four phases:

 _{G1 Phase}  _{S Phase}  _{G2 Phase}  _{M Phase}

 _{Composed of G1, S,}

G2

 Where cell spends

most (~90%) of its time

 _{Often called the}

“resting” phase but cell is not at rest

 Cell is not dividing

 Often called the “resting”

phase but cell is not at rest

 Cell may not be dividing but

 Chromosomes are

stored in the nucleus

 Every cell that

contains a nucleus will have

 Genetic information is

stored on chromosomes

 The coded information

on chromosomes is

called DNA

 Chromatin:

the unwound form of the chromosome

 Condensed:

 Chromosomes unwind

when the cell is not dividing

 _{Unwound chromosomes}

are available to be “read” by the cell’s machinery

 e.g. open book

 the DNA is accessible

 thus the cell can carry out the instructions coded in it

 Not visible under the

microscope

 Condensation occurs at the

beginning of cell division

 Condensed chromosomes

are unavailable to be

“read” (like a closed book)

 visible under the

 Work in groups to model each phase of the cell cycle

using the candies provided

 _{You must should your model to your teacher after}

each phase is taught

 Do NOT eat in the science classroom

Model legend

Licorice =

chromosomes

_{Large plate = cell}

Small plate = nucleus

Other parts to

show, but you will determine how

Centromere

Centrioles

Spindle fibers

Other materials available:

Marshmallow

 Period of rapid growth

 New proteins and organelles are produced

 Chromosomes are unwound (chromatin)

 Cell leaves cell

cycle

 Can be temporary

or permanent

 But not

necessarily dead

 Where a cell

 Cell size must be

large enough

 Environment

 Cell makes a copy of its

entire set of

chromosomes (DNA)

 Q: Why is this

necessary?

 Q: What would the

 Chromsomes that have

duplicated will have two sister chromatids attached to the same centromere

 Sister chromatids

have identical genetic

 _{Cell grows larger in}

size in preparation for cell division

 Produces organelles

and structures needed for cell division

 Example: centrioles

and nucleolus are duplicated

 Shortest part

 DNA is replicated

 Cell size must be

large enough

 Environment

 All of the cell’s energy is

devoted to the process of cell division

 M phase is divided into

mitosis and cytokinesis

 Q: Explain why the

PMAT

 Prophase

 Metaphase

 Anaphase

 Telophase

Overview of Mitosis Animation:

 http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter10/mitosis.html



1. Use candies to represent chromosomes, centrioles, spindle

fibers and nuclear envelope

2. Set up your cell in G2

3. Use additional candy to create structure for prophase 4. Create metaphase structure by making changes to your

prophase structure

5. Create anaphase structure by making changes to your

metaphase structure

6. Create telophase & cytokinesis structure by making changes

 Chromosomes condense

(no longer chromatin) and become visible

 Nuclear envelope

disappears

 Centrioles move to the

poles of the cell

 Spindle fibers begin to

Image is showing:

 Chromosomes

condensing

 Nuclear envelope

disappearing

Illustration is showing:

 Nuclear envelope

disappearing

 Centrioles moving

to poles

 Spindle fibers

 Chromosomes line up

along equator (center of the cell)

 Spindle fibers attach to

 Spindle fibres shorten

pulling the

chromosomes to opposite poles

 Sister chromatids

separate at the

Image is showing:

 Chromosomes

 Chromosomes uncoil

and become invisible

 Nuclear envelope

reappears

 Spindle fibers disappear

 Occurs simultaneously

with cytokinesis

 Daughter cells have

Image is showing:

 Chromosomes

uncoiling

 Nuclear

 Separation of the cell and cell

contents:

 _Cytoplasm  Organelles

 Shows difference between animal and plant

cytokinesis:

 Does not have to be

an equal division

 Daughter cells can:

 _{be different sizes}

 Have different cellular content (but nuclear content is the same)

 Example: budding

 Pinching the cell membrane

forming a furrow

Fluorescence Microscopy

http://micro.magnet.fsu.edu/cells/fluorescencemitosis/cytokinesis2large.html

Green: microtubules

Blue: chromosomes

 Formation of a cell

plate

 Two daughter cells

each containing identical genetic information

 Daughter cells have the

same number of

 The whole process (G1, S, G2, M):

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/ animation__how_the_cell_cycle_works.html

 Mitosis dance:

 Illustrations are only a snapshot in time and

often give the illusion that the phases are

quite distinct but the process is actually fluid.

 Animation:

http://www.johnkyrk.com/mitosis.html

 Stages of Mitosis (by HybridMedical):

For each diagram:

 Identify the stage

of mitosis

 Name one

characteristic that helped you identify the stage

 _{Green: microtubules (spindle fibres and cytoskeleton)}  _{Blue: chromosomes}

 _{Orange: mitochondria}