Cloning and Stem Cells

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Cloning and Stem Cells
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Stem Cells

• Cells that have not yet differentiated into their
  final developmental stage and/or function.
• http//www.youtube.com/watch?vNbjlG84cF1c
• 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
  type.
• http//www.youtube.com/watch?vrVh1FZcZZVk

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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.

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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
  out.
• Placed in a petri dish with the proper nutrients
  cells will develop into specific mature cell
  types Ex heart cells
• http//www.youtube.com/watch?vnm7bVlk4wTo
• Possible uses growing organs, growing neurons
  and muscles, implanting into humans for
  regeneration of organs, studying diseases

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Cloning

• Creating cells, organs, or organisms that are
  exact copies.
• Therapeutic vs. Reproductive
• Therapeutic makes organs and cells for
  transplant, study, and treatment of affected
  individuals.
• 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.

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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.

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Review

• 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.

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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

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Pretranscriptional

• 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
  transcription
• 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)

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Lac operon
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Trp operon
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Review

• What are the chromosome pair in humans that are
  of the same kind but not the same exact sequence
  called?
• What does the repressor in the lac operon bind
  to?
• 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?

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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.
• WRAPPING UP OF CHROMATIN
• DNA is wrapped around histone proteins to form
  beads called nucleosomes.
• Euchromatin loosely wrapped and ready for
  transcription
• Heterochromatin tightly wound and not ready for
  transcription
• 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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(No Transcript)
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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
  pores
• 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

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Review

• 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?

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mRNA modications to become functional
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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.

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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
  develop.
• 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.

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Review

• 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
  II?
• What type of cell would likely want to have long
  lasting mRNA?

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Nondisjunction

• 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.

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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
  significant