1. I can describe the stages of the cell cycle.

Transcription

1 Unit 5 Study Guide Cell Cycle pg I can describe the stages of the cell cycle. Interphase = period in between division G1 = growth phase S = DNA replication G2 = Preparation for division (extra copies of organelles are made, etc.) M Phase = Cell Division Mitosis = Division of the Nucleus: (Prophase Metaphase Anaphase Telophase) Cytokinesis = Division of the Cytoplasm NOTE: Cytokinesis is different in a plant cell vs. an animal cell because of the cell wall. Animal cells form a cleavage furrow (cell membrane pinches in) whereas plant cells form a cell plate (the beginning foundation of a cell wall) Mitosis is nuclear division plus cytokinesis, and produces two identical daughter cells during prophase, prometaphase, metaphase, anaphase, and telophase. Interphase is often included in discussions of mitosis, but interphase is technically not part of mitosis, but rather encompasses stages G1, S, and G2 of the cell cycle. 2. I can describe the structure and function of DNA. DNA is deoxyribonucleic acid. It is the genetic code because it transmits the information needed to build proteins for the cell. Each section of DNA that codes for a protein is called a gene. DNA wrapped around histones (a type of protein) is called Chromatin. A Chromosome is made up of 2 identical sister chromatids (produced during DNA replication) made of chromatin. Chromatin is DNA that is tightly wound around histones. The DNA exists as unraveled Chromatin during most of the cell cycle. It only condenses to form Chromosomes during cell division.

2 Unit 5 Study Guide Cell Cycle pg. 2 DNA is a double helix. This means it is a double-stranded molecule that is twisted like a spiral staircase. A DNA molecule is made of monomers (subunits) called nucleotides. Each nucleotide contains a phosphate group, a sugar (deoxyribose), and 1 of 4 nitrogenous bases (Guanine, Adenine, Cytosine, or Thymine). These nucleotides align so that the sugar and phosphate groups make up the side (backbone) and alternate (S P S P S P). Strong phosphodiester (covalent) bonds hold the phosphates and sugars together. The nitrogen bases are perpendicular to the sugar and form the rungs of the ladder. The nitrogen bases form hydrogen bonds with the complimentary strand of DNA in order to hold the separate strands of the double helix together. The Rule of Base Pairing states that Adenine only bonds with Thymine (A = T) and Guanine only bonds with Cytosine (G = C). Guanine and Adenine are purines, which means that they have a double-ringed structure. Cytosine and Thymine are pyrimidines, which means that they have a single-ringed structure. A pyrimidine (C or T) always bonds with a purine (G or A). The DNA strands run antiparallel to each other, which means that the strands are facing opposite directions. This means that one strand has the 5 end of the sugar at the top of the molecule and the other strand has the 3 end of the sugar at the top. Hydrogen bonds form to create the twisted structure of DNA. Additional Resource: or

3 Unit 5 Study Guide Cell Cycle pg I can explain how DNA is replicated. DNA is replicated during S phase of the cell cycle. The DNA is unwound and replicated in sections called replication bubbles; multiple replication bubbles occur simultaneously in order to speed up the process. Replication is finished when all of the bubbles connect forming two complete identical copies. The process begins at the Point of Origin and proceeds in both directions to form the bubble. GETTING STARTED = Helicase breaks the hydrogen bonds between the strands and unwinds and separates the 2 DNA strands. ADDING DNA NUCLEOTIDES = DNA polymerase is the main enzyme responsible for replication. DNA polymerase adds DNA nucleotides to the new strand. DNA polymerase can only move 3 to 5 on the original strand. PROOFREADING = DNA polymerase also proofreads and corrects mistakes, which are called mutations. RESULT = DNA replication results in 2 identical molecules of DNA, each with one new strand and one original strand. Because only one new strand is made for each molecule, it is called Semi-Conservative replication.

4 Unit 5 Study Guide Cell Cycle pg I can explain what occurs during each phase of mitosis. This means that I can tell the difference between prophase, metaphase, anaphase, and telophase. Prophase = PREP: Chromatin in the nucleus begins to condense and becomes visible in the light microscope as chromosomes. The nucleolus disappears. Centrioles begin moving to opposite ends of the cell and fibers extend from the centromeres. Some fibers cross the cell to form the mitotic spindle. Late Prophase = The nuclear membrane dissolves, marking the beginning of late prophase (sometimes called prometaphase). Proteins attach to the centromeres creating the kinetochores. Microtubules attach at the kinetochores and the chromosomes begin moving. Metaphase = MIDDLE: Spindle fibers align the chromosomes along the middle of the cell nucleus. This line is referred to as the metaphase plate. This organization helps to ensure that in the next phase, when the chromosomes are separated, each new nucleus will receive one copy of each chromosome. Anaphase = APART: The paired chromosomes separate at the kinetochores and move to opposite sides of the cell. Motion results from a combination of kinetochore movement along the spindle microtubules and through the physical interaction of polar microtubules. TELOPHASE = TWO NUCLEI: Chromatids arrive at opposite poles of cell, and new membranes form around the daughter nuclei. The chromosomes disperse and are no longer visible under the light microscope. The spindle fibers disperse, and cytokinesis or the partitioning of the cell may also begin during this stage. 5. I can explain why DNA replication is important for the cell cycle. DNA replication is important because it ensures that EVERY cell that is produced through Mitosis has an exact copy of all of the original DNA. Because the original DNA molecule is used as a template (rule of base pairing), 2 identical molecules of DNA are produced through Mitosis. Both copies of the DNA molecule have an original strand and a new strand that was built following the rule of base pairing (A = T; G = C). This means that all cells in the organism will have the same DNA, therefore the same instructions for making proteins.

5 Unit 5 Study Guide Cell Cycle pg I can identify and label the phase of mitosis given a diagram, model, or using a microscope.

6 Unit 5 Study Guide Cell Cycle pg. 6