Chapter 08 Lecture Outline PDF

Chapter 08 Lecture Outline Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display. 8.1 Prokaryotes Have a Simple Cell Cycle-1 Cell division in prokaryotes takes place in two stages, which together make up a simple c...

Chapter 08 Lecture Outline Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display. 8.1 Prokaryotes Have a Simple Cell Cycle-1 Cell division in prokaryotes takes place in two stages, which together make up a simple cell cycle. 1. Copy the DNA  This process is called replication. 2. Split the cell in two to form daughter cells.  This process is called binary fission. Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display. 8.1 Prokaryotes Have a Simple Cell Cycle-2 The hereditary information in a prokaryote is stored in DNA.  The prokaryotic chromosome is a single circle of DNA.  DNA replication begins with the unzipping of the double-stranded DNA at a point called the origin of replication.  A new double helix is formed by adding complementary nucleotides to the exposed DNA strands that have been unzipped.  The end result of replication is that the cell possesses two complete copies of the hereditary information. Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display. 8.1 Prokaryotes Have a Simple Cell Cycle-3 After replication, the cell grows in order to partition the replicated DNA molecules.  When the cell reaches an appropriate size, the cell splits into two equal halves.  New plasma membrane and cell wall are added at a point between the partitioned DNA.  Eventually the cell constricts in two to form two daughter cells. Each daughter cell is a complete, living cell with its own DNA. Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display. Figure 8.1(a) The prokaryotic cell cycle Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display.  8.2 Eukaryotic Cell Cycle-1 Eukaryotic cells contain more DNA than prokaryotic cells and the DNA is also packaged differently.  Cell division in eukaryotic cells is more complex.  DNA in eukaryotic cells is linear and packaged into a compact chromosome. There is more than one chromosome in a eukaryotic cell. Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display.  8.2 Eukaryotic Cell Cycle-2 Eukaryotic cells undergo two different mechanisms to divide up the DNA.  Mitosis is a cell division mechanism that occurs in nonreproductive cells. These cells are called somatic cells.  Meiosis is a cell division mechanism that occurs in cells that participate in sexual reproduction. These cells are called germ line cells. Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display.  8.2 Eukaryotic Cell Cycle-3 The eukaryotic cell cycle is divided into distinct phases.  Interphase (G1,S, and G2 phases)  Mitosis (M phase)  Cytokinesis (C phase) Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display.  8.2 Eukaryotic Cell Cycle-4 Interphase is comprised of three phases. G1 phase – The primary growth phase of the cell following division – Most cells spend the majority of their lifespan in this phase. S phase – DNA replication occurs in preparation for cell division. G2 phase – Further preparation for cell division, including replication of mitochondria and synthesis of microtubules Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display.  8.2 Eukaryotic Cell Cycle-5 Mitosis (M phase)  A microtubular apparatus binds to the chromosomes and moves them apart. Cytokinesis (C phase)  The cytoplasm divides, creating two daughter cells. Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display. Essential Biological Process 8A: The Cell Cycle Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display.  8.3 Chromosomes-1 Chromosome number varies among organisms.  Most eukaryotes have between 10 and 50 chromosomes in their somatic cells. Chromosomes exist as pairs in somatic cells.  These pairs are called homologous chromosomes, or homologues.  Homologues contain information about the same traits but the information may vary.  Cells that have two of each type of chromosome are called diploid cells. One chromosome of each pair is inherited from the mother and the other is inherited from the father. Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display.  8.3 Chromosomes-2 Prior to cell division, each of the homologous chromosomes replicates, forming two identical copies called sister chromatids.  The sister chromatids are joined together by a structure called a centromere.  Humans have 23 pairs of homologous chromosomes. When each chromosome in the pair is replicated, this makes for a total of 92 chromatids. Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display. Figure 8.2 The difference between homologous chromosomes and sister chromatids Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display.  8.3 Chromosomes-3 A karyotype is an Figure 8.4 The 46 arrangement of chromosomes of a human chromosomes. Chromosomes can be compared based on size, shape, and centromere location. The karyotype on the right shows the 23 pairs of human chromosomes. © SPL/Science Source Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display.  8.3 Chromosomes-4 Chromosomes are comprised of chromatin, a complex of DNA and protein.  There is also some RNA associated with chromosomes.  The DNA in a chromosome is one very long double-stranded fiber that extends unbroken for the length of the chromosome.  The DNA is coiled in order to allow it to fit into a small space despite being very long. Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display.  8.3 Chromosomes-5 DNA is coiled around proteins called histones.  The histones have positive charges to counteract the negative charges associated with the phosphate groups of the DNA. The DNA coils around a core of eight histone proteins to form a complex called a nucleosome.  The nucleosomes in turn can be coiled together further to form ultimately a compact chromosome. Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display.  8.4 Cell Division-1 Interphase sets the stage for cell division.  Chromosomes are first duplicated.  Although not visible, chromosomes begin to wind up tightly in a process called condensation. The cell division that follows interphase is division of the nuclear contents, called mitosis.  Mitosis is a continuous process but it is divided, for ease of study, into four distinct stages. 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display.  8.4 Cell Division-2 Prophase  The condensed chromosomes first become visible with a light microscope.  The nuclear envelope begins to disintegrate.  Centrosomes begin to assemble a network of protein cables called the spindle. Made of microtubules. The microtubules attach to chromosomes. When the process is complete, the sister chromatids of a chromosome are attached by microtubules to opposite poles of the cell. Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display.  8.4 Cell Division-3 Metaphase  The chromosomes attached to microtubules of the spindle are aligned in the center of the cell. The centromeres are aligned along an imaginary plane that divides the cell in half, known as the equatorial plane. Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display.  8.4 Cell Division-4 Anaphase  Centromeres split  Sister chromatids separate  The microtubules of the spindle are dismantled starting at the poles. This pulls the chromatids toward the poles. Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display.  8.4 Cell Division-5 Telophase  The spindle is dismantled.  A nuclear envelope forms around the set of chromosomes at each pole.  The chromosomes begin to decondense.  The nucleolus reappears. Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display. Essential Biological Process 8B: Cell Division © Andrew S. Bajer Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display. Essential Biological Process 8B: Cell Division (continued) © Andrew S. Bajer Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display.  8.4 Cell Division-6 Cytokinesis  Occurs at the end of mitosis and is a division of the cytoplasm into roughly equal halves.  In animals, cytokinesis occurs by actin filaments contracting and pinching the cell in two. This action is evident as a cleavage furrow that appears between the daughter cells.  In plants, a new cell wall is laid down to divide the two daughter cells. The cell wall grows at right angles to the mitotic spindle and is called the cell plate. Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display.  8.4 Cell Division-7 Cells do not live forever. Cells are programmed to undergo division only so many times and then die.  Human cells divide about 50 times. Cancer cells divide uncontrolled. Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display.  8.5 What Is Cancer?-1 Cancer is a growth disorder of cells.  Begins when apparently normal cells grow uncontrollably  Result in a growing cluster of cells called a tumor Malignant tumors are invasive. – Cells from malignant tumors can metastasize, leave and spread to different areas of the body to form new tumors. Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display.  Lung Cancer Figure 8.9 Lung cancer cells (300X) Figure 8.10 Portrait of a tumor Fig 8.9 © Moredun Animal Health LTD/SPL/Science Source Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display.  8.5 What Is Cancer?-2 Cell division is regulated by proteins called growth factors. Cancer is caused by damage to genes the encode growth factors.  Mutation causes damage to genes. May result from chemical or environmental exposure, such as UV rays  Viral exposure may also alter DNA. Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display.  8.5 What Is Cancer?-3 There are two general classes of growth factor genes that are usually involved in cancer. 1. Proto-oncogenes These genes encode proteins that stimulate cell division. When mutated, these genes become oncogenes and can cause cells to divide excessively. 2. Tumor-suppressor genes These genes normally turn off cell division in healthy cells. When mutated, these genes allow uncontrolled cell division. Copyright © 2017 McGraw-Hill Education. Permission required for reproduction or display.