13.1 Biologists have learned to manipulate DNA

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13.1 Biologists have learned to manipulate DNA
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I. The beginnings of DNA technology

• Biotechnology is the use of organisms to perform
  practical tasks for humans
• Much of DNA technology has come from use of
  bacteria called Escherichia coli or E. coli
• 2. Three ways bacteria can include new DNA

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Beginnings of DNA tech

• a. 1940- Joshua Ledgerberg and Edward Tatum
  showed two bacteria can form a tunnel-like
  connection
• b. Viruses can take bacteria DNA from one to
  another bacteria
• c. Can take up loose bacteria from surroundings
• This occurred with Griffiths mice experiment
  with harmless strain bacteria
• B. Recombinant DNA technology combines genes from
  different sources or species into a single
  DNA molecule

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II. DNA technology and frontiers of research in
biology

• A. Human genome- map of all humans genes was
  completed by 2000
• 1. Other organisms sequenced fruit fly,
  yeast, E. coli, or rice plant
• B. Uses
• 1. Improve food nutrition
• 2. Help us understand how our genes work from
  others

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13.2 Biologists can engineer bacteria to make
useful products
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I. Engineering bacteria an introduction

• A. Plasmids are small circle-shape DNA molecule
  separate from larger bacterial chromosomes
• B. Plasmids can be shared between bacteria, for
  example to increase antibiotic resistance

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Plasmids
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Engineering bacteria

• C. Humans use plasmids to place DNA to make
  useful products from bacteria
• 1. Plasmid is removed and the desired gene is
  placed in the plasmid ? recombinant DNA
• 2. Recombinant plasmid is placed back in bacteria
  to replicate over and over- gene cloning

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II. Cutting and pasting DNA

• A. Piece of DNA is cut from desired source by
  restriction enzymes
• 1. In nature used to defend bacteria from foreign
  invading DNA
• 2. Restriction enzymes recognize certain
  sequences to cut eg. GATTC cuts after G
• 3. Usually make staggering cuts exposing a single
  strand known as the sticky end

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Restriction Enzymes
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Cutting DNA

• B. DNA fragment from another source is added
• C. The fragments stick together by base-pairing
  a complementary strand
• D. DNA ligase pastes the fragments together to
  form recombinant DNA molecule

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III. Cloning Recombinant DNA

• A. The Process of cloning recombinant DNA
• 1. Restriction enzymes cuts plasmid in one
  place, human DNA cut in many places with one
  fragment code for protein-V
• 2. Sticky ends of human DNA and plasmid pair
  up by base pairing

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Cloning recombinant DNA

• 3. DNA ligase joins plasmid and human DNA
• 4. Bacterial cell takes up recombinant plasmid
• 5. Many copies of recombinant bacteria are made
  when human gene expressed protein V made

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Gene Cloning
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Cloning recombinant DNA

• B. Libraries of cloned genes
• 1. Genomic library- the complete collection of
  DNA fragments from an organism
• 2. The total of all recombinant plasmids
  contain the entire genome of the organism human

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Genomic Library
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Cloning recombinant DNA

• C. Identifying specific genes with probes
• 1. How do biologist locate a specific gene in
  the library?
• 2. Nucleic acid probe- a complementary
  radioactive nucleic acid strand used to find the
  desired gene sequence
• 3. Heat or chemicals are used to break up DNA
  and probe tags the portion needed

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Nucleic Acid Probe
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13.3 Biologists can genetically engineer plants
and animals
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I. Producing Genetically Modified Plants

• A. Genetically modified organism (GMO)- any
  organism that has gotten one or more genes by
  artificial means
• B. Transgenic- the source of new genetic material
  comes from a different species
• C. Use in plants for delayed ripening, increased
  nutrition, prevent spoiling or resist diseases
• D. Herbicide resistance so they survive when
  fields sprayed for weeds fungi and pest
  resistance as well

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Transgenic Plants
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II. Producing Genetically Modified Animals

• A. More difficult than in plants egg and sperm
  are fertilized and desired trait added to embryo
• B. Use to produce more wool on sheep, leaner
  meat, or mature fish in shorter time
• C. Certain human proteins produced in animals
  milk for human use after purification

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III. Animal Cloning

• A. Plants have been cloned from a simple cutting
  of a plant
• B. An empty egg and a complete nucleus from the
  organism are fused together? exact copy of
  original organism created
• C. Mass production of animals with desired trait

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Animal Cloning
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IV. The GMO controversy

• A. Possible that gene resistance passed onto
  other plants through pollen
• 1. Academy of Science feels that GMO are not a
  threat but needs to be regulated and researched
• B. GM plants and animal products may be slightly
  differ than original possible allergies or
  other negative effects

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13.4 DNA technologies have many applications
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I. Mass-producing DNA

• A. Polymerase chain reaction (PCR)- makes may
  copies of certain DNA segment without living
  cells
• B. Process
• 1. Targeted DNA, nucleotides, DNA polymerase
  and primers are added together
• a. Primers- short strands of DNA that pair
  with known targeted DNA

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Mass producing DNA

• 2. Heat is added to separate or denature the DNA
  strand
• 3. Mixture cools and primers bind to strand
• 4. DNA polymerase adds nucleotides to strands
  producing two DNA molecules
• 5. Procedure is repeated, 2 strands becomes 4
  becomes 8 and so on

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PCR Techniques
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II. Comparing DNA

• A. Gel electrophoresis- sorting molecules by or
  fragments by length
• B. Process
• 1. DNA samples cut up using restriction enzymes
• 2. Few drops are placed in pocket called a well
  at the end of a thin gelatin-like material called
  gel

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Comparing DNA

• 3. Other end is () charge, so the smaller pieces
  of DNA (-) charge move farther in the gel
• 4. Gel is stained to make DNA visible under UV
  light
• 5. Fragments show up as bands in the lanes

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Gel Electrophoresis
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Comparing DNA

• C. Genetic markers
• 1. Used to tell different in bands between
  samples
• 2. May use radioactive DNA labels to tag genetic
  markers
• 3. Genetic markers- specific portion of DNA
  varies from individual
• a. May analyze to look at recessive disease
  as a carrier

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Comparing DNA

• D. DNA fingerprinting unique banding pattern on
  gel, determined by restriction fragments of a
  persons DNA
• 1. Markers found in alleles for disease or in the
  introns (noncoding) regions
• 2. To use DNA he genetic markers that are not
  shared with others are used
• 3. DNA specimen from hair follicle or blood
• 4. 1 in 100,000 to 1 billion chance that two
  people have the same number of genetic markers

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13.5 Control mechanisms switch genes on off
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I. Regulation of Genes in Prokaryotes

• A. Bacteria do not have ability to turn genes on
  or off, but can change functions based on
  environment
• 1. E. Coli makes three enzymes
• in presence of milk, does not
• when milk not present

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Gene Regulation in Prokaryotes

• B. Genetics of breaking milk sugar / lactose into
  an usuable form
• (Fig. 13-18)
• 1.Operon- cluster of genes along
• with control sequence genes
• a. lac operon includes two control genes and 3
  genes for enzyme production are located

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Regulation of genes
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Gene Regulation in Prokaryotes

• 2. Promoter- first control sequence where RNA
  polymerase (makes mRNA) attaches itself to DNA
• 3. Operator- second control gene, like a switch,
  that determines if RNA polymerase can attach to
  the promoter

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Lac Operon repressor
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Gene Regulation in Prokaryotes

• C. Activation or Repression of the lac operon
• (Fig. 13-19)
• 1. Repressor- a protein that binds to the
  operator and blocks the attachment of RNA
  polymerase
• 2. If lactose is absent then repressor is present
  and turns off the lac operon
• 3. If lactose is present then it binds to the
  repressor protein and changes the shape of the
  repressor

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Gene Regulation in Prokaryotes

• a. When the repressor changes shape it no longer
  binds to the operator
• b. The operator is open and RNA polymerase binds
  to the promoter
• c. The lactose processing genes are turned on
• d. When lactose is no longer present the
  repressor can rebind to the operator
• D. Prokaryotes waste little energy on unnecessary
  reactions due to many different operons

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II. Regulation of Genes in Eukaryotes

• A. More elaborate and complicated than in
  prokaryotes
• B. Eukaryotic DNA includes promoter sequences
  before the point that transcription takes place
• C. Transcription factors- regulate transcription
  by binding to promoters or RNA polymerases
• D. Transcription factors are activated and
  deactivated by certain chemical signals in the
  cell
• 1. Hormones may attach to
  transcription factors
• to signal gene expression- the
  transcription
• and translation of genes into
  proteins

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III. From Egg to Organism

• A.Gene expression begins when an egg is
  fertilized and divides
• 1.The position of each new cell in the embryo
  promotes expression of particular groups of genes
• 2.Genes affecting the head are only expressed in
  the pre-head region
• 3.A cells position relative to its neighboring
  cells affects its gene expression

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Active Genes
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From Egg to Organism

• B. Cellular differentiation- cells become
  increasingly specialized in structure and
  function
• 1.Glycolysis gene expressed in all cell types,
  while insulin gene expressed pancreas cells
• 2.Hemoglobin gene would not be expressed in eye
  lens, nerve cell, or pancreas cell
• C. DNA chip- help biologist track which genes are
  turned on in a given cel

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IV. Stem Cells

• A. Stem cells- cells that have the ability to
  differentiate into various types of cells
• B. Blastocyst- embryo of about 100 cells,
  comprised mostly of stem cells

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Stem Cells

• C. Most stem cells differentiate into different
  cell types, yet bone marrow has them in adulthood
• 1. Stem cells in bone marrow differentiate into
  different types of blood cells
• 2. Bone marrow transplants help people with
  leukemia
• D. Stem cells either from embryonic or adult stem
  cells may help to fight other disease as well
• 1. Ethical debates surround the use of stem
  cells

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V. Homeotic Genes

• A. Homeotic genes- master control genes that
  direct development of body parts in specific
  locations
• 1. Homeobox- nucleotide sequence that codes for
  a protein that promotes the transcription ofgenes
  involved in the development of specific body
  parts
• 2. A mutation in the Drosphila fruit fly
  homeobox can lead to eyes developing where legs
  or wings or antenna should be.

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Homeotic Genes
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