THE CELL CYCLE

All organisms have a life cycle: birth growth reproduction death

Within all organisms, cells are also “born”, grow, reproduce/divide, and die. CELL TYPE LIFE SPAN Lining of the intestine 4-5 days Skin cell 2 weeks Red blood cell 4 months Liver cell 300-500 days Brain cells 100 years Brain cells do not divide… you are born with all your brain cells you will ever have!

Cell Cycle - cells are born - cells grow and work - cells divide to make new cells - cells die

CANCER: Uncontrolled Cell Growth a disorder in which body cells lose the ability to control cell growth and cell division. Cancer cells do not respond to signals that regulate their cell cycle; As a result cells divide uncontrollably.

Before a cell divides, it must…. The cell copies its DNA . At the end of this stage, the nucleus contains two complete sets of DNA.

During DNA replication….. C --- G & T --- A G --- C

Perform DNA replication on the following DNA strand: T G A T T C G T A G C C A A C T A A G C A T C G G T

Perform DNA replication G A C --- A C T G

Perform DNA replication G A C --- A T --- A C T G --- C G --- --- T A --- --- A T --- --- C --- G --- T A --- G --- --- C --- T --- A

Perform DNA replication G A C --- A C T G

Perform DNA replication G A C --- A T --- A C T G --- C G --- --- T A --- --- A T --- --- C --- G --- T A --- G --- --- C --- T --- A

DNA Replication

DNA Replication

CELL DIVISION MITOSIS

Why do cells undergo mitosis? To make new cells… To replace old or dead cells To replace cells destroyed by injury Skin cells

for growth and development.

to produce a new individual --- asexual reproduction the production of genetically identically offspring from a single parent…a clone.

MITOSIS pmat There are four phases in mitosis: 1. prophase 2. metaphase 3. anaphase 4. telophase pmat

Before mitosis, DNA must be… duplicated cell DNA Replication cell

Prophase The duplicated chromosomes condense. cell

Metaphase Chromosomes line up along the middle of the cell.

Anaphase Chromosomes are pulled apart and move to opposite ends of the cell.

Telophase The chromosomes gather at opposite poles of the cell forming two nuclei.

Cytokinesis The cytoplasm divides, forming two identical cells.

telophase

cytokinesis

metaphase

anaphase

interphase

prophase

MEIOSIS

Why do cells undergo meiosis? To make egg and sperm for sexual reproduction gametes Eggs are made in the ________ ovaries Sperm are made in the _______ testes

Body Cells vs Gametes 46 chromosomes 23 chromosomes Homologous pairs Mom & Dad pairs Homologous pairs Unpaired chromosomes Diploid cell Haploid cell

A Body cell A diploid cell Homologous pairs

A sex cell A Gamete --- _________ A haploid cell Half the chromosomes

MEIOSIS 1 4 2n diploid cell haploid cell (gametes) n n n n 24 chromosomes 12 chromosomes

Interphase Meiosis I Meiosis II DNA Replication Homologous chromosomes separate DNA/Chromosomes duplicate Sister chromatids separate

MEIOSIS There are eight phases in meiosis: 1. prophase I 2. metaphase I 3. anaphase I 4. telophase I Meiosis I - - - 5. prophase II 6. metaphase II 7. anaphase II 8. telophase II Meiosis II - - -

1. Prophase I Crossing-over Homologous chromosomes pair up

2. Metaphase I middle

3. Anaphase I Homologous chromosomes separate middle

4. Telophase I cytokinesis

5. Prophase II

6. Metaphase II middle

7. Anaphase II middle

8. Telophase II End result: Four haploid cell (n) Each of the four cells is genetically different from each other and from the parent cell.

& Asexual reproduction MITOSIS vs MEIOSIS Makes body cells & Asexual reproduction Makes gametes (egg & sperm) 24 12 12 24 24 24 12 12 1 cell 2 cell 1 cell 4 cell 24 chromosomes 24 chromosomes 24 chromosomes 12 chromosomes Asexual reproduction produces identical offspring …no genetic diversity Sexual reproduction produces genetical different offspring …large genetic diversity