MODELS ALLOW US TO UNDERSTAND THE RELATIONSHIPS BETWEEN REPRODUCTION, HEREDITY AND DIVERSITY. Lesson #2

THE LIFE OF A CELL

Cell cycle

ALL CELLS HAVE A SPECIFIC FUNCTION

Can you think of some examples?

SPECIALIZED/DIFFERENTIATED CELLS

1. Specific function

2. Specific structrure

CELL LIVE, DO THEIR FUNCTION AND SOMETIMES DIVIDE…

Why do cells need to divide?

NOT ALL CELLS DIVIDE

Which cells divide?And why?

ANSWERSWHICH CELLS ??

1. Unicellular organisms (eukaryotes and prokaryotes)

2. Most specialized cells (G0) in multicelullar organisms, except some (cardiac muscle, neurons, gametes…).

3. Stem cells (non-differentiated cells which divide to produce different types of cells.)

WHY ??

4. Asexual reproduction of unicelular organisms

5. Growth multicelullar organisms

6. Increase in the amount of specific cells.

7. Regeneration or cell replacement

TWO MAIN MOMENTS IN THE CELL LIFEInterphase: development

Mitotic phase: division

CELL CYCLE

INTERPHASE During this stage the cell grows, develops more organelles, DNA is duplicated and centrosomes duplicate. The cell becomes ready for the next division.

It is the longest stage of the cell cycle

The nucleus has the usual structure

There are 3 distinguished phases during Interphase:

G1: Cell growth, organelles and cytoplasm substances duplicate

S: DNA replication

G2: Cell checks for error in replication, finishes duplicating centrosomes. Ready for division.

G0 is a stage in which the cell stops dividing and is metabolically active

Images: http://scienceaid.co.uk/biology/cell/cycle.html

MITOTIC PHASEMitosis: nuclear division

1 cell nucleus divides into 2 identical nuclei. Same DNA.

Cytokinesis: Division of the cytoplasm

EXERCISE 1 How many cells are in Interphase?

How many cells are in the Mitotic phase?

MITO

TIC

PHASE

CELL CYCLE