Cell Cycle and Cancer for Videos (PDF)

HONORS  SB1. Obtain, evaluate, and communicate information to analyze the nature of the relationships between structures and functions in living By Mrs. cells. Hoskins b. Develop and use models to explain the role of cellular reproduction...

HONORS  SB1. Obtain, evaluate, and communicate information to analyze the nature of the relationships between structures and functions in living By Mrs. cells. Hoskins b. Develop and use models to explain the role of cellular reproduction (including binary fission, mitosis, and meiosis) in maintaining genetic continuity How does this happen?? It all begins with a fertilized egg Once the sperm fertilizes the egg, that fertilized egg (zygote) goes through cell division repeatedly. Cell division through mitosis gives rise to many identical cells. Differentiation: a process that creates special structures and functions. – Specialized cells become tissues  organs  organ systems. It all begins with a fertilized egg  Cell Differentiation Stem cells = undifferentiated cells that can become differentiated into one or more types of specialized cells. – Two Types: Embryonic stem cells: cells that have never differentiated Adult stem cells: cells found in adult bone marrow that are partially differentiated and can become bone, blood, cartilage, fat, and connective tissue  Cell Differentiation Implanted blastocyst becomes a gastrula = embryo with 3 differentiated germ layers Organogenesis = the process of body organ and organ system formation that follows gastrulation  Cell Differentiation Organism: one individual member of a species Organ System: set of organs working together for a common function (Ex. digestive system) Organ: set of tissues working together for a common function (Ex. stomach) Tissue: group of cells working together for a common function (Ex. muscle tissue) Cell: most basic unit of life that has all the characteristics of life. (Ex. muscle cell)  Cell Cycle Cell Cycle = a repeated pattern of growth, DNA duplication and cell division that occurs in eukaryotic cells. 2 purposes = GROWTH and REPAIR The Cell Cycle consists of 3 main phases: – Interphase = cell growth – Mitosis = cell division – Cytokinesis = cytoplasm separation which begins at the end of mitosis  Cell Cycle Interphase Interphase = the growth phase of the cell cycle. 3 parts: – G1 phase = Gap 1 phase = cell grows and makes proteins – S phase = Synthesis phase = DNA replication occurs, doubling the number of chromosomes – G2 phase = Gap 2 phase = more cell growth and protein synthesis **At the end of interphase the cell has 2 full sets of chromosomes!**  DNA vocabulary Chromosome: one long continuous thread of DNA that consists of thousands of genes and regulatory information. – Gene = a section of DNA that contains the instructions for making a protein – Each human body cell has all of your DNA organized into 46 chromosomes. In normal body cells, chromosomes always occur in pairs of homologous chromosomes Your DNA, Half of your chromosomes (23 organized in 46 in each cell) came chromosomes from your and thousands biological mother of genes, and half from your provides the biological father. instructions for This is why they making proteins, often occur in which run your pairs. body.  DNA vocabulary Chromatid – one half of a duplicated chromosome. – Sister Chromatids – two identical chromatids Centromere – region of the condensed chromosomes that looks pinched. Telomere – ends of the DNA molecule.  Cell Cycle A closer look at S phase Unduplicated homologous chromosomes Duplicated homologous chromosomes DNA Replication During S phase of Interphase **Because of S phase, at the end of interphase the cell has 2 full Sister chromatids Sister chromatids sets of chromosomes!**  Cell Cycle MITOSIS Mitosis = the division phase of the cell cycle. - 1 cell becomes 2 identical daughter cells  Cell Cycle MITOSIS Prophase Metaphase Anaphase Telophase Cytokinesis begins  Cell Cycle Prophase Chromosomes condense & are visible as sister chromatids (in X’s). Nuclear membrane disappears. Spindle fibers form out of centrioles.  Cell Cycle Metaphase Spindle fibers connect to the centromere of each sister chromatid. Chromosomes line up in middle of the cell.  Cell Cycle Anaphase Sister chromatids separate, pulling away from each other and becoming individual chromosomes. Chromatids move to opposite ends of the cell.  Cell Cycle Telophase Chromosomes decondense and start to look like chromatin again (threadlike instead of rodlike) Nuclear membrane re- forms around chromosomes at each pole. Spindle fibers break down. Cytokinesis begins.  Cell Cycle Cytokinesis The division of the cytoplasm into 2 individual cells. In plant cells – cell plate forms midway between divided nuclei and gradually develops into a membrane. End result = 2 identical In animal cells - forms a body cells cleavage furrow that pinches the cell into 2 equal parts. How often do cells divide? Every cell divides at a different rate based on its need. Examples: – Internal lining of intestines = 5 days – Skin cells = every 2 weeks – Red blood cells = 4 months – Liver cells = 1 year Why do body cells divide? **Growth and repair** – Cells can’t just get bigger to grow either – they have to stay small to maintain a high surface area to volume ratio. This is most efficient energy-wise and allows substances to move in and out of the cell more easily. How do cells know when to divide and when not to? What happens if this regulation fails? Regulation of the Cell Cycle Cell cycle is controlled by a chemical control system that starts & stops events in the cell cycle. – Proteins play a key role! Regulation is: – External – signals that come from outside of the cell; Ex. Hormone, nutrients, etc. – Internal – signals that come from the cell’s own nucleus; Ex. DNA inside of the cell  Checkpoints Checkpoint – critical point where “stop” & “go” signals can regulate the cycle. M G2 G1 Key: Note: Cell G1 = Gap 1 of S division is mostly interphase S = S phase of in the “off” interphase position in G0 animal cells if G2 = Gap 2 of (Restin there is no interphase g stimulus present.  Apoptosis Apoptosis = programmed cell death – Internal/external signals activate genes that produce self-destructive enzymes. – Nucleus shrinks and breaks apart. – Ex: Web fingers & toes during development  Cancer Cancer = uncontrolled cell division – Happens when the regulation of the cell cycle breaks down. – Cancer cells divide much more often than healthy cells do. – Leads to the formation of tumors. Tumors = clumps of cells that divide uncontrollably  Tumors Benign – abnormal cells typically remain clustered together – It may be harmless & easily removed Malignant – cancer cells that break away from the tumor and move to other parts of the body  more tumors – Metastasize = spreading of disease from one organ to others  Causes Many things can cause cancer, such as: – Biological factors Ex. Age, inherited genetic mutations, skin type, etc. – Lifestyle choices Ex. Diet, physical activity, exposure to UV radiation, etc. – Viruses and other infections Ex. HPV can cause cervical cancer – Exposure to carcinogens = cancer causing agents; chemicals that cause cancer by mutating DNA Ex. Tobacco smoke, asbestos, etc.  Practice Cell Cycle A Closer look at Cancer stations