Cell Cycle & Checkpoints Lecture 1

Eukaryotic organisms Heritable information is passed to the next generation via processes that include cell cycle and mitosis or meiosis plus fertilization

Cell Reproduction Cell division (MITOSIS) –process that forms new cells from one cell –results in two cells that are identical to the original, parent cell.

Importance of Cell Reproduction Growth (increase in size) Repair (replace dead or damaged cells) Asexual reproduction

Cell Cycle Sequence of growth and division of a cell –Growth period= Interphase –Nuclear Division= mitosis

Interphase Cell grows in size Carries on metabolism Chromosomes duplicate (synthesis of DNA) Preparation for mitosis (actual division into 2 identical cells)

INTERPHASE = G 1, S, G 2 G 1 - Gap 1 Grow by producing proteins & organelles G 2 - Gap 2 Grow Produce molecules & organelles needed for cell division S- Synthesis DNA replication Some can return to cycle with signal (external or internal signals) (Ex; Liver cells respond to injury) Some never divide again (Ex: Mature nerve, muscle cells) MITOSIS G 0 - Cell leaves cycle and stops dividing Most body cells in this phase

Cyclin-dependent kinases (Cdk’s) are present all the time but inactive unless combined with cyclins Presence of MPF (mitosis promoting factor) triggers passage past G 1 & G 2 checkpoints KINASES- Enzymes that work by adding a phosphate group to other molecules

Cyclin levels change throughout cell cycle Fluctuating levels of different Cyclin-Cdk complexes seem to control all stages of cell cycle

Cancer Lecture 2

CANCER CELLS Don’t respond to control signals Lose density-dependent inhibition Lose anchorage dependence Telomerase enzymes maintain/replace telomeres Transformation- process that changes a normal cell into a cancer cell

Telomeres protect DNA from being degraded Telomeres become shorter with each replication; shorter in older cells Telomerase enzyme lengthens telomeres Cancer cells have increased telomerase activity Jack Szostak Carol Greider Elizabeth Blackburn Nobel Prize Physiology/Medicine Discovery of Telomeres

Most cells divide times in culture; then stop, age, die Cancer cells are “immortal” -HeLa cells from a tumor removed from a woman (Henrietta Lacks) in 1951 are still reproducing in culture

Phases of Mitosis Lecture 3

Phases of Mitosis Occurs after DNA replication Mitosis is a continuous process of replication, alignment and separation. Produce 2 genetically identical cells (each cell has the same genome)

Phases of Mitosis Prophase Metaphase Anaphase Telophase

Prophase Chromatin (DNA) coils to form visible chromosomes –Sister chromatids visible held together by centromere Spindle fibers Disappearing nuclear envelope Doubled chromosome

Section 8.2 Summary – pages Chromosomes line up in middle of cell (chromosome alignment) Centromere Sister chromatids Metaphase

Section 8.2 Summary – pages Centromeres split sister chromatids pulled apart to opposite sides of cell Anaphase

Two daughter cells form Cells separate Cells proceed into the next interphase Nuclear envelope reappears Two daughter cells are formed Telophase

Section 8.2 Summary – pages end of telophase cytoplasm and organelles divide Occurs differently in plants and animals Cytokinesis

Section 8.2 Summary – pages Unicellular organisms remain as single cells. In multicellular organisms, cell growth and reproduction result in groups of cells that work together as tissue to perform a specific function. Results of Mitosis Cells  Tissues  Organs  Organ Systems