Cell Growth and Reproduction Cells cannot survive if

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Cell Growth and Reproduction

Cell Growth and Reproduction

 • Cells cannot survive if there is not enough DNA • Cells divide

• Cells cannot survive if there is not enough DNA • Cells divide before they become too big to function properly

Cell Reproduction • Cell division is a process in which new cells are produced

Cell Reproduction • Cell division is a process in which new cells are produced from one cell • Diagram: – 2 daughter cells are identical to the original parent cell

Discovery of Chromosomes • before cells divide, several short, stringy structures suddenly appear inside

Discovery of Chromosomes • before cells divide, several short, stringy structures suddenly appear inside the nucleus – vanish right after the cell divides – called chromosomes • contain DNA • carriers of genetic material • copied and passed through generations of cells

 • Has 2 halves called sister chromatids –Held together by a centromere

• Has 2 halves called sister chromatids –Held together by a centromere

 • Chromosomes usually exist as chromatin – long strands of DNA wrapped around

• Chromosomes usually exist as chromatin – long strands of DNA wrapped around histone proteins – Coils up into visible chromosomes during mitosis (cell division)

Cell Cycle • Sequence of the growth and division of a cell • 2

Cell Cycle • Sequence of the growth and division of a cell • 2 general periods Mitosis G 2 G 1 S

Growth (called Interphase) • Majority of cell’s life spent in this phase • Cell

Growth (called Interphase) • Majority of cell’s life spent in this phase • Cell grows in size • Carries on metabolism • Chromosomes are duplicated

Interphase • Busiest phase • Divided into 3 parts – G 1 Phase: rapid

Interphase • Busiest phase • Divided into 3 parts – G 1 Phase: rapid growth and metabolic activity • Cell grows • High production of proteins – S Phase: DNA synthesis and replication • Cell copies its chromosomes – G 2 Phase: Cell prepares for division • Organelles are made • Centrioles replicate

Division (called Mitosis) • Nuclear division • 2 daughter cells are formed from 1

Division (called Mitosis) • Nuclear division • 2 daughter cells are formed from 1 parent cell

Prophase • 1 st phase (longest) • chromosomes become visible – centrioles separate to

Prophase • 1 st phase (longest) • chromosomes become visible – centrioles separate to opposite sides of the nucleus (in animal cells only) • nucleus begins to disappear – nuclear envelope and nucleolus begin to disintegrate • spindle forms role in separating sister chromatids

Metaphase • Chromosomes become attached to the spindle fibers by a centromere • Chromosomes

Metaphase • Chromosomes become attached to the spindle fibers by a centromere • Chromosomes begin to line up in the middle of the cell • Very short phase (lasts a few minutes)

Anaphase • Centromeres split apart • Separation of sister chromatids from each other •

Anaphase • Centromeres split apart • Separation of sister chromatids from each other • Shortening of spindle fibers • Individual chromosomes result in 2 groups

Telophase • Final phase of mitosis • Chromosomes unwind (become a tangle of material)

Telophase • Final phase of mitosis • Chromosomes unwind (become a tangle of material) • Spindle breaks down • Nucleolus reappears • New nuclear envelope forms around the chromosomes • Membrane forms between 2 nuclei

Cytokinesis • Cell’s cytoplasm divides • Usually occurs at the same time as telophase

Cytokinesis • Cell’s cytoplasm divides • Usually occurs at the same time as telophase • Animal cells: plasma membrane pinches in along the middle of the cell • Plant cells: – Have rigid cell wall – Cell plate goes across the center of the cell – Cell membrane forms around each cell – New cell wall forms on each side of cell plate

Animal Cell

Animal Cell

Plant Cell

Plant Cell

Control of Cell Cycle • Cells can lose control of the cell cycle –

Control of Cell Cycle • Cells can lose control of the cell cycle – Can result from failure o produce certain enzymes, overproduction of enzymes, or producing enzymes at the wrong time – leads to uncontrolled cell division (called cancer) • Genes: segment of DNA that controls production of proteins like enzymes

Cancer • Result of uncontrolled cell division • Forms masses of tissue called tumors

Cancer • Result of uncontrolled cell division • Forms masses of tissue called tumors – Deprives normal cells of their nutrients • Metastasis: cancer spreads throughout body infecting circulatory system • 2 nd leading cause of death • Can affect any tissue in the body

Causes of Cancer • Environmental – Cigarette smoke – Air and water pollution –

Causes of Cancer • Environmental – Cigarette smoke – Air and water pollution – Exposure to UV radiation – Damages genes that controls cell cycle • Genetic – Viral diseases and infections can damage genes

Cancer Prevention • Diets low in fat and high in fiber • Vitamins and

Cancer Prevention • Diets low in fat and high in fiber • Vitamins and minerals