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1.27.11 Genetics The Cell Cycle What is the Cell Cycle? The regular sequence of growth and division that cells undergo is known as the cell cycle. Organisms grown and maintain themselves by cell division (or making new cells) What is the Cell Cycle? Regular sequence of growth and division that cells undergo. CELL CYCLE Organisms grow and maintain themselves by cell division Mitosis is the basic process of cell division For each new daughter cell, the cycle begins again with interphase. STAGES OF THE CELL CYCLE Interphase Mitosis Cytokenesis TWO DAUGHTER CELLS ONE CELL What’s a Chromosome? Remember how DNA is found in the nucleus of a cell? When DNA condenses and coils up really tight, it makes a chromosome. CHROMOSOMES Body cells have a full set of chromosomes. Full Set = Diploid # Sex cells have a half set. Half Set = Haploid # CHROMOSOMES For Humans, the diploid number is 46. For humans the haploid number is 23 Different organisms have different diploid and haploid numbers because they have different numbers of chromsomes. Structure of Chromosomes Chromatids: the 2 identical parts of a chromosome Centromere: the middle, round part of the chromosome that holds the sister chromatids together Centromere Sister chromatids Sister chromatids CENTROMERE It’s in the center! INTERPHASE Growing: The cell grows to its full size and produces structures it needs. Copying DNA: Cells make an extra copy of the DNA in its nucleus in a Process called replication. Replication is important because each new cell, called a daughter cell, must have a complete set of DNA to survive (46 chromosomes) Preparing for Division: Cells produce structures that it will use to divide into 2 new cells. Interphase How many cells does it take to make a human? EGG SPERM How do we get more? MITOSIS MAIN IDEA It’s Mitosis! Cells Divide in 2 Each New Daughter Cell Has Identical Chromosomes 2 Types of Cells Body cells: all cells in the human body except sex cells •Have a full set of chromosomes Ex: muscle cell, brain cell, skin cell Sex cells: sperm and egg cells •Have a half set of chromosomes Mitosis Mitosis: process in which a body cell divides into 2 identical daughter cells •The goal is to make new body cells Phases of Mitosis Interphase 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase Cytokinesis Mitosis daughter cells Prophase (1st Phase of Mitosis) Prophase (1st Phase of Mitosis) Mitosis begins. DNA condenses from stringy DNA into rodlike structures Prophase (1st Phase of Mitosis) • Mitosis begins. • Chromosomes condense from stringy DNA into rodlike structures. • Nuclear membrane disappears. spindle DNA (chromosomes) Metaphase (2nd Phase of Mitosis) • The chromosomes line up across the center of the cell. • Each chromosome is connected to a spindle fiber at its centromere. Spindle Anaphase (3rd Phase of Mitosis) The sister chromatids separate and move to opposite sides of the cell. Telophase (4th Phase of Mitosis) • A nuclear membrane forms around each set of chromosomes. Telophase (4th Step of Mitosis) • A nucleus forms on each side • The chromosomes go back to stringy shape. Cytokinesis • The cell pinches in half. • Each daughter cell has an identical set of chromosomes. CYTOKINESIS (the cytoplasm pinches and splits in 2) Prophase? Metaphase? Anaphase? Telophase? 1 3 2 4 5 6 Prophase? Metaphase? Anaphase? Telophase? 1 2 5 3 6 4 7 Mitosis Paper Plate Model Groups of 2 Mitosis Microscope Lab & Paper Plate Model 2 groups (rotating) – 20 minutes each