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Gene Regulation and Genomics

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Gene Regulation and Genomics Differentiation As development progresses, cells becomes more specialized and restricted in the expression of their genetic content. – PowerPoint PPT presentation

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Title: Gene Regulation and Genomics


1
Gene Regulation and Genomics
2
Differentiation
  • As development progresses, cells becomes more
    specialized and restricted in the expression of
    their genetic content. This leads to many types
    of cells in a complex organism.
  • However, differentiated cell may retain all their
    genetic potential.
  • Salamanders can regenerate a lost limb.
  • Tissue culture has allowed many plants to
    beproduced from a single plant.

3
Plant Tissue Culture
  • This is BIG business, and is very important in
    the horticultural industry.
  • Thirty years ago if an orchid breeder had a
    spectacular plant it might produce two or three
    asexual off-shoots per year. Each of these could
    be sold for, perhaps, 150-200. Sounds good?
  • Today that same plant can be placed in tissue
    culture and the grower can produce 20,000
    identical plants, sell them for 10 each.
  • 200,000 vs. 300-400?? You choose.
  • The center for plant tissue culture in Florida is
    the area around Apopka.
  • The process is simple in theory, but more
    complicated in practice. What growth medium is
    required? What part of the plant yields the best
    cells for tissue culture? At what rate and how
    long are cells shaken in solution? Etc.

4
Theres a lot of information in that cell! How
can we regulate its use?
  • In eukaryotes the cells genes are located on
    chromosomes.
  • A chromosome consists of DNA and histones.
    Histone proteins are a framework around which the
    DNA can be tightly coiled. The term for the
    bead-like DNA-histone complex that can be seen in
    electron micrographs is termed a nucleosome.
  • The tight packing of the DNA in the chromosome
    helps to regulate gene expression by preventing
    transcription proteins from contacting the DNA.
    Only when portions of the DNA uncoil can
    transcription of information occur.

5
Alternative RNA splicing
  • Remember the DNA message that is copied contain
    both introns and exons.
  • The introns are removed to produce a functional
    mRNA.
  • If splicing occurs in different ways, different
    mRNAs are produced and their products will also
    be different.
  • This means that alternative RNA splicing can
    allow a gene to code for several different
    peptide chains, depending upon how the
    information is spliced together.

6
A Cell is not a Simple Strucuture!
  • After mRNA is produced other events will happen.
  • mRNA must be broken down. When this happens is
    regulated by the cell.
  • When translation actually occurs can be
    controlled by the cell.
  • The peptide that is formed during translation may
    need to be bent, folded, or chemically altered
    before it becomes functional.
  • Proteins may be destroyed by the cell after a set
    period of time.
  • These mechanisms enable the cell to control the
    amount and the type of protein that is active in
    the cell at any given point in time.

7
Reproductive Cloning
  • Reproductive cloning adds a nucleus from a donor
    cell to an egg cell, whose nucleus has bee
    removed.
  • The result is a new animal exactly like the
    parent (i.e. Dolly , the sheep)
  • The technique is not without problems , and its
    usefulness is still to be proven.
  • There are great ethical concerns about human
    cloning, and most researchers are strongly
    opposed to it. (Would you really want another
    you, and would you be you if you did get
    cloned??) Thats a lot of you!

8
Therapeutic cloning
  • Unlike reproductive cloning, therapeutic cloning
    has great medical potential.
  • In this procedure stem cells (adult and/or
    embryonic) are cultured in the lab, and then
    induced to transform into specialized tissues.
  • The use of embryonic stem cells has much promise,
    but much of this has been lost in the current
    moral and ethical debates.
  • If one is truly opposed to embryonic stem cell
    research, one should also be ethically boound to
    forgo the use of any therapies or cures that
    result from it.

9
Signal Transduction Pathway
  • How do cell know when to differentiate?
  • How are cellular activities regulated within an
    organism?
  • The processes is relatively straightforward
  • A signal molecule, produced elsewhere, attaches
    to a receptor protein on the cell membrane.
  • This causes a cascade of reactions between relay
    proteins in the cells interior.
  • The last relay molecule activates a transcription
    factor that causes the transcription of a
    specific gene in the DNA of the nucleus.
  • This leads to the production of a protein that
    may act as an enzyme or structural element needed
    to effect a change in the cell.

10
Oncogenes
  • Oncogenes are cancer causing genes, and usually
    trigger increased production of cell growth
    factors.
  • Active oncogenes, along with defective
    tumor-supressor genes, can lead to the
    development of cancerous tumors.
  • Usually cancer is the result of multiple
    mutations in a somatic cell.
  • Many cells probably develop these mutations, but
    are detected by cells of the immune system and
    eliminated before that can give rise to a tumor.
  • The next slides has two illustrations of steps in
    tumor development.

11
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12
Tumor suppressor gene
  • If a gene that inhibits cell division is
    defective, it can lead to the uncontrolled
    replication of cells and the development of a
    tumor.
  • This is seen in the illustration below.

13
Carcinogens
  • Many factors can cause DNA mutations that lead to
    tumor development. These factors are called
    carcinogens.
  • Carcinogens can be physical factors, such as,
    X-rays, UV radiation, and radiation from radon
    (naturally occurring) or nuclear weapons
    (man-made).
  • They can be chemical factors, like the chemicals
    in tobacco, or cleaning agents, such as benzene.
  • Even some viruses can lead to cancer. Cervical
    cancer is one example. This is the reason for
    the development of a vaccine against sexually
    transmitted viruses.
  • Avoidance of risk factors is one way to decrease
    the chance of developing cancer.

14
Genomics, the study of whole sets of genes
  • DNA technology has lead to the development of the
    field of genomic research. This research has
    many potential applications in the areas of
    medicine, agriculture, forensic science, and
    production of products for industrial and
    pharmacological uses.
  • With the development of these lines of research,
    a host of legal, ethical, social, and
    environmental issues have arisen. It may take
    years, if not decades, to resolve many of the
    concerns that individuals are voicing today.
  • None the less, DNA technology and genomics is one
    of the most exciting areas of modern biology.

15
Recombinant DNA Technology
  • Plasmids are circular DNA molecules found in
    bacteria which can be used to insert genes into
    bacterial cells.
  • The genes that are inserted can come from many
    sources other than bacteria.
  • This technology has allowed the insertion of
    genes into bacteria, which can then be grown in
    great quantity, yield large amounts of the
    product for which that gene codes.
  • This procedure can also yield large quantities of
    cells that carry gene that chaanges something
    aboutr the cell in which it is found.
  • A diagram of this process can be seen in the next
    slide.

16
Using plasmids to copy genes and make proteins
17
Restriction enzymes
  • To get a piece of DNA containing the gene to be
    studied, the DNA is cut into pieces using
    restriction enzymes.
  • These enzymes recognize short segments of DNA and
    cut the DNA at those points.
  • Because the cuts are staggered, there are
    unattached bases at the ends (sticky ends)
  • New DNA pieces can attach to the sticky ends, and
    then DNA ligase covalently bonds the pieces
    together.

18
  • The process of inserting and cloning a gene can
    be seen in the illustration to the right.
  • Note that once the plastid has a gene inserted
    into its DNA, and the plastid is put into a
    bacterium, tremendous numbers of bacteria
    containing the gene can be produced in a short
    period of time.

19
How to make a clean gene!
  • Remember, when you copy a DNA gene it consists of
    introns and exons. You need to remove the
    introns to get a clean piece of mRNA.
  • To get a gene to clone, one must isolate the
    clean mRNA, and then use reverse transcriptase
    to make a DNA copy of the mRNA.
  • After the RNA is removed, a complementary stand
    of DNA is formed. The result is double-stranded
    cDNA.

20
Uses of Recombinant DNA Technology
  • Both bacterial cells and mammalian cells have
    been used to generate useful products. Mammalian
    cells can be genetically engineered so that the
    desired protein is secreted in the animals milk.
    The product can then be isolated from the milk
    and used.

21
Gel Electrophoresis
  • One technique for studying DNA uses a thin gel to
    separate DNA based on size and electrical charge.
    A DNA sample is introduced into a well in the
    gel, and a high voltage current causes the
    molecule to migrate through the gel. The
    finished gels can be stained and photographed.
    Samples can be compared using the migration
    patterns that are present.

22
DNA Fingerprints
  • The use of DNA evidence in forensic science has
    become very widespread.
  • The chance of two individuals having the same DNA
    pattern is extremely small if enough markers are
    used.
  • DNA matches have enabled the identification of
    the victims of tragedies such as, plane crashes,
    9-11, ethnic cleansing.
  • Innocent persons on death row have been freed due
    to DNA evidence which proved their innocence.

23
Gene Therapy
  • There has been much hope for effective gene
    therapy. It could allow the body to compensate
    for genes that are defective or non-functional.
  • At present success has been very limited, and
    some clinical trials have been discontinued due
    to unforeseen problems.
  • Will gene therapy place a significant role in the
    future of medicine? Only time will tell.

24
Polymerase Chain Reaction (PCR)
  • This technique has allowed researchers to take a
    minute amount of DNA and, from it, produce a
    large quantity of DNA for analysis.
  • Using a series of enzymes and cycles of heating
    and cooling, new copies of DNA are created. A
    complete cycle only takes a few minutes,
    therefore in a few hours the number of DNA
    molecules produced is tremendous. (calculate how
    many you would have after 20 cycles)

25
Human Genome Project
  • No one in todays world should leave a basic
    biology course and not be aware of the Human
    Genome Project, its purpose and its potential for
    mankind.
  • Purpose map out the entire nucleotide sequence
    of the DNA of the human chromosome.
  • This was completed years ahead of schedule due to
    the rapid development of techniques in
    sequencing.
  • Potential insight into human development
    insight into evolutionary relationships and .
  • better diagnosis and treatment of many of our
    commonest and most debilitating diseases.
  • Go to the links provided in this lesson to
    explore the Human Genome Project and the whole
    field of genomics.

26
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28
Pros and Cons of Genetically Modified Organisms
  • Since the advent of the first genetically
    modified crops, questions of environmental impact
    and risks to health have surfaced repeatedly.
  • The EU (European Union) has a very strong bias
    against GM crops. There is the concern that
    transgenic crops could endanger individuals with
    food allergies. You could consume a food not
    knowing that it contained an allergen that could
    trigger a severe and dangerous reaction.
  • China has made wide use of GM crops. If you need
    to feed 1,300,000,000 people, high yield may be
    more important than the slight chance of
    mortality due to food allergy.
  • There are many other concerns and benefits that
    we as a society will have to carefully weight as
    we move into this uncharted era GM plants and
    animals.

29
This represents the information known to be
located on chromosomes 9 and 4. The graphics
are courtesy of the U.S. Dept. of Energy, Genome
Management Information System of the Oak Ridge
National Lab
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