Cellular ReproductionThe Cell Cycle & Mitosis

9 - Ch.9 – Cellular Reproduction 9.1 – Cellular Growth

9 - Ch.9 – Cellular Reproduction 9.1 – Cellular Growth

Genetic MaterialSome key terms…Genome – All of the cell’s

DNA/inheritable traitsChromosomes – Smaller

packages of DNA moleculesSomatic Cells – Body cells which

have a full set of chromosomes (2n)

Gametes – Reproductive cells which have ½ the number of chromosomes (n)

Chromatin – DNA and protein molecules (histones)

9 - Ch.9 – Cellular Reproduction 9.1 – Cellular Growth

Cells duplicate their genetic material

before they divide, ensuring that each

daughter cell receives an exact

copy of DNA

9 - Ch.9 – Cellular Reproduction 9.1 – Cellular Growth

Cell Cycle (The life cycle of a cell)

Broken into 2 partsInterphase

Mitosis

Period when the cell grows, carries out its

cellular functions and replicates DNA in

preparation for cellular division

Period when the nucleus & nuclear material

divides.

Cytokinesis occurs near the end of mitosis. It is

the dividing of the cytoplasm.

9 - Ch.9 – Cellular Reproduction 9.1 – Cellular Growth

Cell Cycle (The life cycle of a cell)

Period when the cell grows, carries out its

cellular functions and replicates DNA in

preparation for cellular division

Period when the nucleus & nuclear material

divides.

Cytokinesis occurs near the end of mitosis. It is

the dividing of the cytoplasm.

Broken into 2 partsInterphase

Mitosis

9 - Ch.9 – Cellular Reproduction 9.1 – Cellular Growth

Interphase

G1 (1st Gap) Phase – Growth & normal cell

function

S (Synthesis) Phase – DNA is copied

G2 (2nd Gap) Phase – Cell prepares for division

of its nucleus

•Protein for microtubules is synthesized•Additional cell growth•Cell “checks” the DNA to be sure that it was copied correctly so that mitosis can begin

MitosisCan be broken

down into 5 phases

Prop

hase

Prom

etaph

ase Metaphase Anaphase

Telophase

Division of the nuclear material

9 - Ch.9 – Cellular Reproduction 9.2 – Mitosis & Cytokinesis

PROPHASE•Chromatin condenses•Nucleolus disappears•Spindle fibers begin to form•Centrioles separate

9 - Ch.9 – Cellular Reproduction 9.2 – Mitosis & Cytokinesis

PROMETAPHASE•Nuclear envelope fragments•Centrioles near the poles•Chromosomes begin to attach to the spindle fibers at the kinectochore (a protein located at the centromere)

9 - Ch.9 – Cellular Reproduction 9.2 – Mitosis & Cytokinesis

METAPHASE

•Longest stage of mitosis (~20min.)•Duplicated chromosomes align at the metaphase plate (equator of the cell)

9 - Ch.9 – Cellular Reproduction 9.2 – Mitosis & Cytokinesis

ANAPHASE•Shortest stage of mitosis (~2min.)•Sister chromatids are separated and are pulled to the poles•The cell elongates•By the end of anaphase each pole has one copy of each chromosome

9 - Ch.9 – Cellular Reproduction 9.2 – Mitosis & Cytokinesis

TELOPHASE

•Nuclear membranes form•Nucleoli reappear•The chromosomes become less condensed (unwind)

9 - Ch.9 – Cellular Reproduction 9.2 – Mitosis & Cytokinesis

Mitosis in Plant Cells

9 - Ch.9 – Cellular Reproduction 9.2 – Mitosis & Cytokinesis

CYTOKINESIS Starts during telophase

9 - Ch.9 – Cellular Reproduction 9.3 – Cell Cycle RegulationCell Cycle Regulation

G1 checkpoint•Ensures…

•Enough nutrients•Large enough to divide

•If “go” signal is given cell will divide•If go signal is not given cell will enter the G0 (non-dividing) phase

G2 checkpoint•Ensures…

•DNA was copied correctly in the S-phase

M checkpoint•Ensures…

•All sister chromatids are connected properly at the kinetochore

9 - Ch.9 – Cellular Reproduction 9.3 – Cell Cycle RegulationThe Cell Cycle Clock

Controlled by cyclins and cyclin-dependent kinases

Proteins that build up and then

degrade at certain points in the cell

cycle

(Cdk)Enzymes the cyclins bind to in order to initiate the

next the next phase in the cell cycle

9 - Ch.9 – Cellular Reproduction 9.3 – Cell Cycle RegulationThe Cell Cycle Clock

Internal and external factors trigger cell division

Internal Growth factors - proteins released by certain cells that stimulate other cells

to divide. (Growth hormones in mammals)

ExternalSpace and available

nutrientsAn anchor point (for most

animal cells)

Cancer…

9 - Ch.9 – Cellular Reproduction 9.3 – Cell Cycle RegulationWhat happens when cells lose the

ability to control the cell cycle?

Cells can become cancerous when a mutation occurs spontaneously or from an outside factor (carcinogen)

As cells multiply a predictable series of genetic changes occur

9 - Ch.9 – Cellular Reproduction 9.3 – Cell Cycle RegulationThese changes ultimately lead to the mutation of two

types of genes that control the cell cycle… Oncogenes and tumor-suppressor genes

Benign Tumor – does not invade

surrounding tissue

Malignant Tumor – invades surrounding

tissue and spreads via circulatory or lymph

system

10 billion to 100 billion

cells.Usually takes

decades to cause a

problem in humans