A. Review Materials 1. Text: Chapter 2, section 3. 2. EOS questions: cell division and DNA (online) 3. Any videos linked from the website 4. Labs: review conclusions and notes (DNA Candy, Flipbooks, Scum) B. How living things grow? 1. A single cell grows and then divides, forming two cells. Those two cells grow and divide, and so on 2. This process occurs in all living things and is called the cell cycle. 3. There are three STAGES in the cell cycle: interphase, mitosis, and cytokinesis. 4. There are four PHASES in mitosis: prophase, metaphase, anaphase, and telophase. The Cell Cycle
Summary: See diagram on page 58-59 1) Extra organelles are made and DNA is copied. 2) Equal amounts of organelles and a copy of each DNA is passed two either side of the cell. 3) The cell splits. Voila! Two identical cells!!! Interphase 1) The cell grows 2) Extra organelles are made (ribosomes, mitochondria, chloroplasts in plant cells) 3) DNA is copied (replication) 4) The centriole is copied Mitosis Prophase 1) chromatin (genetic material: DNA molecules) bundle up to form chromatids. 2) Centrioles move to opposite ends of the cell 3) Spindle fibers form a bridge from centriole to centriole 4) The nuclear envelope breaks down 5) 2 identical sister chromatids (bundles of DNA molecules) attach to each other with a centromere to form a chromosome.
Metaphase 1) The chromosomes line up across the center of the cell. 2) Each chromosome attaches to a spindle fiber at its centromere. Anaphase 1) The centromeres split. 2) The 2 chromatids separate. 3) One identical chromatid is pulled to one side of the cell by the spindle fiber (the centriole reels in the spindle fiber attached to the chromatid like a fisherman reeling in a fish!) 4) The cell stretches out Telophase 1) The chromosomes begin to unravel into chromatin and lose their rodlike appearance. 2) A new nuclear envelope forms around the chromosomes.
Cytokinesis 1) The cell membrane pinches around the middle of the cell. 2) The cell splits in two. 3) Voila!!! Two daughter cells with identical DNA and equal numbers of organelles. DNA (deoxyribose nucleic acid) 1. DNA is an organic compound that is found in the the nucleus of the cell. 2. It is the blueprint for the cell which means that it carries all the instructions which tell the cell how it will be constructed and how it will function. 3. Looks like a twisted ladder or spiral staircase (p.61) called a double helix. 4. The 6 ingredients (components) of DNA: deoxyribose (sugar), phosphate, nitrogen bases (guanine, cytosine, adenine, thymine). a. sides of ladder made of sugar called deoxyribose and phosphate. b. the rungs of the ladder (called a double helix ) are made of nitrogen bases c. nitrogen bases: ATGC A = adenine T = thymine G = guanine C = cytosine
c. bases on one side of ladder pair up with the other d. A only pairs with T and G only with C 5. DNA Replication ( replicate means copy): takes place in the nucleus (see page 62) A=orange T=blue G=green C=yellow [ ] The 2 sides of double helix of DNA unzip The nitrogen bases floating in the nucleus pair up with the bases on each half of the DNA molecule (A pairs with T and G with C) An exact copy is made!
Chromatid Nucleus Mitosis: Prophase Centromere Chromatin (individual DNA molecules) bundle up to form chromatids which are attached by a centromere to form a chromosome. Cell unbundled = chromatin Individual DNA Molecule
Chromosome Centromeres (hold the identical sister chromatids together making a chromosome) ( sister chromatids) Chromatin (individual DNA molecules) bundles up to form chromatids. Each chromatid in a chromosome is identical.