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interdiction Hershey and chase Experiment The phage lytic cycle of phage T4 lysogenic cycle HIV reproductive cycle The genetics of bacteria.

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Presentation on theme: "interdiction Hershey and chase Experiment The phage lytic cycle of phage T4 lysogenic cycle HIV reproductive cycle The genetics of bacteria."— Presentation transcript:

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2 interdiction Hershey and chase Experiment The phage lytic cycle of phage T4 lysogenic cycle HIV reproductive cycle The genetics of bacteria

3 Prokaryotes Prokaryotes (from Old Greek pro- before + karyon nut or kernel, referring to the cell nucleus) mean before nucleus)Old Greek nutkernel The prokaryotes are divided into two domains: the bacteria and the archaea. bacteriaarchaea bacteria archaea

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5 FUNCTIONSTRUCTURE protects the cell and gives shapeCell Wall protects the cell against some antibiotics (only present in Gram negative cells) Outer Membrane regulates movement of materials into and out of the cell; contains enzymes important to cellular respiration Cell Membrane contains DNA, ribosomes, and organic compounds required to carry out life processes Cytoplasm a region where it carries genetic information inherited from past generations nucleoid protects the cell and assist in attaching the cell to other surfaces Capsule, and slime layer assist the cell in attaching to other surfaces, which is important for genetic recombination Pilus (Pili) moves the cellFlagellum contains some genes obtain through genetic recombinationPlasmid

6 Hershey and chase Experiment

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8 Alfred Day Hershey was born on December 4th, 1908, in Owosso, Michigan. He studied at the Michigan State College, where he obtained B.S. in 1930, and Ph.D. in In 1967 he got an honorary D.Sc. at the University of Chicago. field :bacteriologist field :bacteriologist and geneticist. geneticist awarded the Nobel Prize in Physiology or Medicine in 1969, Alfred D. Hershey died on May 22, 1997.

9 Martha Cowles Chase (1927 – August 8, 2003) She was August Chase was only in her 20s when she worked with biologist Alfred D. Hershey on the "blender experiments" at the Cold Spring Harbor Laboratory in New York."blender experiments" Chase was only in her 20s when she worked with biologist Alfred D. Hershey on the "blender experiments" at the Cold Spring Harbor Laboratory in New York."blender experiments" Chase received her bachelor's degree in biology from the College of Wooster in Ohio, and her post-doctoral degree at the University of Southern California. her scientific career ended when she experienced suffering from dementiaendeddementia her scientific career ended when she experienced suffering from dementia

10 When Hershey moved to Cold Spring Harbor, New York, in 1950 Department of Genetics, where he performed the famous Hershey-Chase blender experiment with Martha ChaseCold Spring Harbor, New York1950Hershey-Chase blender experimentMartha Chase When Hershey moved to Cold Spring Harbor, New York, in 1950 Department of Genetics, where he performed the famous Hershey-Chase blender experiment with Martha ChaseCold Spring Harbor, New York1950Hershey-Chase blender experimentMartha Chase

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12 In 1953, Alfred Hershey and Martha Chase confirmed DNA's preeminent role in genetics by demonstrating that DNA is the genetic material of a virus called phage T2.

13 The phage (A virus that infects bacteria; also called a bacteriophage.), which infects E. coli, consists of a head, sheath, tail, and base plate made of different proteins. DNA is packaged within the head of the virus.phage The phage (A virus that infects bacteria; also called a bacteriophage.), which infects E. coli, consists of a head, sheath, tail, and base plate made of different proteins. DNA is packaged within the head of the virus.phage

14 When T2 comes in contact with E. coli : the phage attaches to the bacterium by its tail. Next, the phage injects genetic material into the cell. The genetic material directs bacterial enzymes to produce viral offspring. When the life cycle is complete, 100 to 200 progeny phages have been assembled inside each bacterium. The bacterium breaks open, or lyses, and the phages are released. Since T2 consists of only DNA and protein, Hershey and Chase reasoned that the genetic material must be one of the two components. So they designed an experiment to determine which it is.

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17 Hershey and chase concluded that the DNA of the virus is injected in the host cell during infection, leaving the protein outside. The injected DNA provides genetic information that make the cell produce new viral DNA and protein to make new viruses

18 The phage lytic cycle of phage T4

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20 Lysogentic and lytic cycles of phage lambda

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22 HIV reproductive cycle

23 "HIV" stands for Human Immunodeficiency Virus. Many people also refer to HIV as the "AIDS virus." What Is HIV? HIV lives in blood and other body fluids that contain blood or white blood cells. People have gotten HIV through: uunprotected sexual intercourse with an HIV-infected person. ssharing drug injection equipment. iinfected blood used in transfusions. PPregnancy. ttransplanted organs from infected donors. How Is the Virus Transmitted?

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25 The genetics of bacteria

26 Two different kinds of genetic material exist: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). deoxyribonucleic acidribonucleic acid Prokaryotic genetic material is organized in a simple circular DNA molecule (the bacterial chromosome) in the nucleoid region of the cytoplasm. chromosomenucleoid region The genetics of bacteria

27 Replication begins a fixed point called the origin. In most prokaryotes, the DNA has only one origin point. The uncoiling of the two strands of the circular molecule begins at the point of origin and progresses in opposite directions (bidirectional). This is helped by the enzyme called DNA gyrase As a result, the circular DNA appears as the Greek letter q (theta) during replication

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29 Some bacteria also transfer genetic material between cells. 3 primary ways to transfer genetic material between bacteria: 1. Transformation 2. Transduction 3. Conjugation

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