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Cloning and Stem Cells


Cloning and Stem Cells – PowerPoint PPT presentation

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Title: Cloning and Stem Cells

Cloning and Stem Cells
Stem Cells
  • Cells that have not yet differentiated into their
    final developmental stage and/or function.
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  • Totipotent Can be come any type of cell
    totally potent, plant cells have more of this
    leading to cuttings of leaves developing into
    whole plants. The fertilized egg and first 8
    cells or so are totipotent. This means that a
    cell can be removed from the 8 cell stage to do
    genetic testing and the embryo can develop
    normally as the cells left are totipotent.
  • Pluripotent Can become more than one type of
    cell plural potency. Stem cells in the bone
    marrow that will become blood cells can become
    more than one kind of white or red blood cell
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Stem Cells characteristics
  • Can divide indefinitely
  • Give rise to more than one mature cell type
  • Blood, liver, skin, intestinal lining
  • Can be cultured in petri dishes
  • Telomeres become worn down over divisions so
    embryonic are more useful.

Embryonic vs. Stem cells
  • Embryonic stem cells have divided less so there
    chromosome ends (telomeres) are longer. This
    leads to a much higher success level in culturing
    and less likelihood of the stem cell line dying
  • Placed in a petri dish with the proper nutrients
    cells will develop into specific mature cell
    types Ex heart cells
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  • Possible uses growing organs, growing neurons
    and muscles, implanting into humans for
    regeneration of organs, studying diseases

  • Creating cells, organs, or organisms that are
    exact copies.
  • Therapeutic vs. Reproductive
  • Therapeutic makes organs and cells for
    transplant, study, and treatment of affected
  • Reproductive makes a whole new organism such as
    Dolly (the sheep), pigs for parts like heart
    valves, and other farm animals to produce
    products, drugs, and other needed molecules.

Steps to clone a mammal
  • Need three organisms
  • 1 donor of egg (nucleus
  • Will be removed)
  • 2 donor of cell with
  • Nucleus to be put into
  • Empty egg of 1
  • 3 surrogate sheep that
  • Will have implanted
  • Embryo that will grow.

  • What type of cloning makes organs for transplant?
  • How can you get stem cells in culture to develop
    into one kind of mature cell?
  • What cells in a human are totipotent?
  • What are the protective ends of a chromosome that
    shorten over time as each round of replication
    cant duplicate the complete DNA strand?
  • What enzyme found in Cancer cells and gamete
    producing cells can add to these ends to restore
    them to their normal starting length?
  • What is the term for the place where golgi bodies
    line up to conduct cytokinesis in plant cells.

Control of gene expression
  • Gene expression transcription and translation
  • Transcription makes RNA from DNA
  • Translation makes protein from RNA
  • We must control the making of proteins so that
    they are made in the proper amounts at the proper
    time and in the proper cells. All organisms have
    mechanisms for this.
  • Pretranscriptional controls
  • Posttranscriptional controls
  • Post translational controls

  • Prokaryotic cells
  • OPERON- a series of genes controlling the making
    of more than one polypeptide using one promoter.
  • Promoter-DNA where RNA polymerase binds to start
  • Operator- DNA where repressor binds to stop
  • Operon- all of the DNA in this unit together
  • Inducer- molecule that binds to repressor to make
    it useless"
  • Inducible operon lac operon, is typically off
    but can be induced to go on when a molecule is
    present that needs to be broken down (lactose
    sugar present needs to make lactase enzyme)
  • Repressible operon trp operon, is typically on
    but can be repressed to go off when the product
    of the reaction is already present (tryptophan
    amino acid already present)

Lac operon
Trp operon
  • What are the chromosome pair in humans that are
    of the same kind but not the same exact sequence
  • What does the repressor in the lac operon bind
  • What needs to bind to the represser for the lac
    operon to be expressed?
  • What are the two steps of gene expression?
  • What is the inactivated X chromosome called?
  • What are the proteins called that DNA binds to
    for packaging?
  • What stage are cells in that are no longer part
    of the typical cell cycle such as adult neurons?

Eukarytoic pretranscriptional control
  • Eukaryotic cells
  • Promoter- Where the RNA polymerase binds
  • ENHANCERS- Activator proteins bind to enhancer
    DNA at a point away from the promoter which then
    bends the DNA to allow it to bind to the promoter
    and to allow the RNA polymerase to bind.
  • SILENCERS- section of DNA where repressor
    proteins can bind to stop transcription
  • TRANSCRIPTION FACTORS- molecules that bind to the
    promoter which allows the RNA polymerase to
    attach more easily. They bind to the TATA box on
    the promoter.
  • DNA is wrapped around histone proteins to form
    beads called nucleosomes.
  • Euchromatin loosely wrapped and ready for
  • Heterochromatin tightly wound and not ready for
  • DNA methylation adding CH3 methyl groups makes
    DNA unaccessible
  • Histone Acetylation adding C2H3O2 acetyl groups
    to the histone proteins that the DNA is bound to
    makes them loosen their grip and transcription
    can go faster.

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Post Transcriptional
  • Eukaryotic cells only as no nuclear membrane in
    prokaryotic cells means it will start translation
    even before transcription is completed.
  • Primary transcript of RNA is made into functional
    mRNA transcript. Controlling this process
    controls transcription.
  • GTP cap on 5 end (phosphate end) of mRNA to
    allow it to attach to the ribosome
  • Poly A tail on 3 end (sugar end) of the mRNA to
    help it make its way through the small nuclear
  • Spliceosome (small nuclear riboproteins snrps)
    remove introns and splice together exons
  • Sometimes exons can be altneratively spliced to
    create a different protein in translation ABCD
    sections can be ADBC

  • What is added to the sugar end of a primary
    transcript? (3 end)
  • What is cut out by snrps?
  • What process is started by the binding of a
    molecule to the promoter?
  • What is mRNA called before it is modified to
    become funcitonal?
  • What phase of meiosis does synapsis happen?
  • What binds to silencer DNA?
  • How many chromosomes are there in anaphase?

mRNA modications to become functional
Translational controls
  • Breakdown of mRNA timing varies red blood cells
    mRNA very long lasting as they need to make
    hemoglobin for life and that is almost their
    entire job so no control is needed.
  • Initiation of translation Sometimes need
    molecule to help assemble tertiary structure such
    as heme group in hemoglobin with its Iron.
  • Protein activation Golgi polypeptides need to
    be altered to make them functional.
  • Protein breakdown after the final protein is
    made it can be degraded or last longer depending
    on function.

Animal body development
  • Gradient of regulatory proteins leads to
    segmentation of all animals.
  • Homeotic genes master switches then determine
    which segment will become what.
  • Homeboxes a short string of nucleotides within
    the homeotic gene that can trigger a group of
    genes that lead to an appendage or major organ to
  • One homeotic gene triggers the growth of an eye
    and if it is broken no eye develops. The
    homeotic eye master switch can be transplanted
    from humans to mice to trigger eye development in
    the mouse. The homeobox genes in the mouse are
    still the same so it is a mouse eye and not a
    human eye.

  • What are the master switches called that
    determine the segment development of animals?
  • What are the segments of DNA that repressors bind
    to in the lac and trp operon called?
  • What are the molecules that bind to the TATA box
    of the promoter in eukaryotic cells called?
  • Where in the cell does translation take place?
  • How many tetrads would line up during metaphase
  • What type of cell would likely want to have long
    lasting mRNA?

  • Chromsomes fail to divide properly during meiosis
    so a fertilized egg ends up with an extra
    (trisomy) or missing (monosomy) chromosome.
  • Ex. Down syndrome where a person has an extra
    21st chromosome so they have 47 total. Most
    problems lead to death, but the sex chromosomes
    have more survival.

Sex Chromosome nondisjunction
  • Turner syndrome XO O represents missing
    chromosome female, webbing, short and
    undeveloped, very serious.
  • Klinefelters syndrome XXY Male with some
    female secondary characteristics not as severe.
  • XXX superfemale no issues
  • XYY maybe more aggressive, but not too