What events occur during each of the four phases of mitosis? The Cell Cycle What events occur during each of the four phases of mitosis?

Characteristics of living organisms All Living things, including individual cells, can reproduce. Reproduction is the process by which cells or organisms make more cells or organisms like themselves. Unicellular Organisms: Cell reproduction produces a new organism Multicellular Organisms: cell reproduction is used for growth and to replace damaged or dying cells. Living things are: Based on a genetic code Grow and develop Respond to their environment Made up of cells Reproduce Maintain a stable internal environment= homeostasis Obtain and use material and energy Taken as a group, living things evolve *In your notes, fill out this graphic organizer for the 8 characteristics of living things.

Prokaryotic Cell Division: Simple Binary Fission Cell’s genetic information is copied, then the cell splits in two. Two new cells identical to parents cell. Bacteria ASEXUAL REPRODUCTION Paramecium cell division In Mitosis: Cells divide among non-sex cells

Chromatin Chromatids Chromosomes DNA > In your notes, write the difference between each of the orange words found on this page. Chromosomes DNA

DNA Chromatin Chromosomes Sister Chromatids Blueprint of life, nucleic acid Chromatin granular genetic material, spread out in nucleus of non-dividing cells. Cannot be seen with microscope Chromosomes condensed genetic material in dividing cells Can be seen Sister Chromatids Identical copies of Chromosomes joined by a centromere (“centro-” middle)

The Cell Cycle: The Cell Cycle If a cell simply divided into two, would each of the new daughter cells have all the chromosomes as the original cell (parent cell)? Eukaryotic cells are multicellular, which means copying their chromosomes is much more complex. The Cell Cycle Interphase- growth and preparation Mitosis- cell division Cytokinesis- division of cytoplasm, formation of two cells.

Interphase Cell spends MOST of life here, growing and preparing to divide Three parts: G1= Gap 1= Cell Grows and carries out routine functions increase in cell size S= Synthesis phase= cell’s chromosomes are copied. “Critical Stage” if duplicated incorrectly centrioles also duplicated G2= Gap 2= Cell prepares for the nucleus to divide Produces extra organelles and cytoplasm in preparation for division

Cell Cycle Checkpoints There are checkpoints throughout the cell cycle G1, S, G2, M Make sure cell is ready to move onto the next phase (has all necessary organelles, copied DNA, etc.) Once the cell has past the G1 checkpoint, it will complete the cell cycle Some cells stay in the G1 phase all their life (muscle cell, brain cells) Cell Cycle Checkpoints

Cell Cycle Regulators Cyclins Protein that regulates the timing of the cell cycle in eukaryotic cells Levels of cyclins rise and fall throughout the cell cycle Cyclin-dependent Kinases (cdks) Enzymes that are activated when they bind with cyclin and they make the cell cycle continue

Regulators Internal Factors within the cell that control cell cycle Cyclin and CDKs Allow cell cycle to proceed only when certain processes have occurred Replication of chromosomes Chromosome Attachment to spindle before anaphase External Factors Outside the cell Growth factors molecules that bind to cell surface that signal cell to divide Similar cells have molecules that have opposite effect so that when it becomes to crowded, cells stop dividing

Consists of mitosis and cytokinesis Cell Division Produces two daughter cells Usually takes place quickly Two stages Mitosis= division of cell nucleus, this is how organisms repair tissue and grow and develop Cytokinesis= division of cell cytoplasm Can overlap, so that cytokinesis occurs as Mitosis is still happening. Nerve cells- non dividing Muscle cells- non dividing Skin cells- divide all the time Digestive tract cells- divide all the time M Phase Consists of mitosis and cytokinesis

Life Span of Some Human Cells Cell type Life span Cell division Lining of esophagus 2-3 days Can divide Lining of small intestine 1-2 days Lining of the large intestine 6 days Red blood cells Less than 120 days Cannot divide White blood cells 10 hours to decades Many do not divide Smooth muscle Long-lived Cardiac (heart) muscle Skeletal muscle Neurons (nerve) cells Most do not divide