Genetics Exam 1 Outline for Pierce Benjamin A Chapters 2 3 4 Genetics Essentials Concepts and Connections 2nd ed New York W H Freeman 2013 N pag Print CHAPTER 2 Cohesion holds the sister chromatids together o until severed by a molecular knife called separase o two resulting chromosome separate cell divides Errors in chromosome separation are often catastrophic o Cancer o Reproductive failure o Child with severe handicaps 2 major organism groups o 1 prokaryotic usually 1 chromosome o 2 eukaryotic more than 1 chromosome More complex cell division Mitosis and meiosis processes Compartmentalized cell structure Components bound by intracellular membranes Unicellular or multicellular organisms Prokaryotes 2 distinct types of bacteria o 1 eubacteria true bacteria o 2 Archaea ancient bacteria o Distinctly different DNA Eukaryotic cells have a nuclear envelope with DNA to form a nucleus DNA is close to other cell components in prokaryotic cells DNA and histone protein complex chromatin In eukaryotic DNA and histones together form tightly wound packed chromosomes o In eukaryotic chromosomes Histone proteins enable DNA to fit in nucleus also they make reproduction more complicated Histones must separate before DNA can be accessed Archaea also have some histone proteins Eubacteria don t have histones o Not highly ordered tight DNA o Simpler copying reading Prokaryotic cells generally have DNA arranged as a ring o A few bacteria have more than one chromosome o Bacterial DNA located on other DNA molecules are called plasmids Eukaryotic chromosomes multiple in number and linear Some eukaryotic genes are on circular DNA found in organelles o Mitochondria chloroplasts Viruses are neither prokaryotic or eukaryotic because they don t possess a cellular structure o Outer protein coat surrounding DNA or RNA Eukaryotic chromosomes are multiple in number and complex Some eukaryotic genes are on circular DNA found in organelles o Mitochondria chloroplasts Viruses are neither prok Or euk Because they don t possess a cellular structure o Have an outer protein coat surrounding DNA or RNA o They can only reproduce within host cells o suggests that viruses evolved from their hosts rather than from other viruses Close relationship between the genes of virus and host 3 fundamental cell reproduction events o 1 copy genetic information o 2 separate copies o 3 cell must divide Prok Cell division o The circular chromosome replicates o Cell divides in a process called binary fission Origin of replication site where DNA replication begins o Origins of the 2 newly replicated chromosomes move to opposite ends of the cell o New cell wall forms between them o 2 cells identical copies of the parent cell Euk Cell division o Nuclear matrix highly organized internal scaffolding in the nucleus network of protein fibers maintains space proportions between nuclear components takes part in DNA replication expression of genes modification of exiting gene products in most eukaryotic cells 2 sets of chromosomes o product of sexual reproduction each chromosome in one set has a corresponding chromosome in the other set o together create a homologous pair o Two chromosomes of a homologous pair are usually alike in structure size carrying genetic info For the same set of hereditary traits Esp Sex chromosomes SETSS S Eukaryotic chromosomes are highly folded condensed o Some would be several cm long 1000x the nucleus diameter o DNA histone proteins rod shaped chromosome a functional chromosome has 3 main parts o 1 centromere o 2 pair of telomeres o 3 origins of replication the centromere is the attachment point for spindle microtubules filaments which move chromosomes during cell division before cell division occurs a kinetochore multiprotein complex attaches to the centromere o later spindle microtubules attach to the kinetochore on the basis of centromere location on the chromosome 4 classified types one of the 2 arms of a chromosome the short arm of the submetacentric or acrocentric chromosome is designated by the letter p and the other by the letter q telomeres natural tips of a linear chromosome o protect and stabilize the ends sister chromatids 2 newly replicated chromosome CELL CYCLE MITOSIS cell cycle a cell s life the stages through which it passes from one division to the next through the cell cycle genetic instructions for all characteristics are passed from parent to daughter cells each new cell metabolizes grows and develops end of the cell cycle is cell division replication checkpoints key transition points in the cell cycle where regulation occurs o have the ability to prohibit the cell from proceeding to the next stage o necessary to prevent cells with damaged or missing chromosomes from proliferating proliferate to grow produce by multiplication of parts defects in checkpoints can lead to unregulated cell growth some cancers 2 major phases of the cell cycle and functions o 1 Interphase period between cell division in which the cell grows develops o 2 M mitosis Phase active cell division Includes mitosis nuclear division and cytokinesis cytoplasmic division INTERPHASE Long period of growth and development G1 cell grows proteins necessary for cell division are made 3 phases G1 S G2 o Typically lasts 7 hours G1 S checkpoint near end of G1 Checkpoint holds in cell in G1 until the cell has all necessary enzymes for DNA replication o Cell is committed to divide once it passes this checkpoint Before G1 S CP cells may exit from active cell pass into a nondividing phase called G0 by regulatory signals G0 stable states Cells remain a constant size o Cells can remain here indefinitely or return back to G1 and the active cell cycle Many cells never enter G0 S Phase DNA synthesis Each chromosome replicates o Before S phase each chromosome is unreplicated o After S phase each chromosome is composed of two chromatids G2 gap 2 several biochemical events necessary for division occur G2 M checkpoint near end of G2 Checkpoint is only passed if the cell s DNA is undamaged After cell passes it enters the M phase The length of interphase varies between cell types o Ex typical mammalian cell spends 10 hours in G1 9 hours in S and 4 hours in Throughout interphase chromosomes are tightly coiled yet relaxed G2 M PHASE MITOSIS The sister chromatids separate and the cell undergoes division Separation results in a complete set of genetic information for each new cell M phase has 6 stages o 5 stages of mitosis cytokinesis 5 stages prophase
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