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Genetics in the News
New York Times, August 25 2004
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AUGUST 26, 2004!!
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Building Better Bodies
By NICHOLAS D. KRISTOF
Published: August 25, 2004 New York Times
For a glimpse of what post-human athletes may look
like beginning in the 2012 or 2016 Olympics, take a
look at an obscure breed of cattle called the Belgian
Blue.
Belgian Blues are unlike any other cows you’ve ever
seen. They have a genetic mutation that means
they do not have effective myostatin, a substance
that curbs muscle growth. Belgian Blues are all
bulging muscles without a spot of fat…
Gene therapies are being developed that would block
myostatin in humans, and they offer immense
promise in treating muscular dystrophy and the
frailty that comes with aging.
But once this gene therapy becomes available for
people who really need it, it’ll take about 10
minutes before athletes are surreptitiously using it,
….particularly because in contrast to today’s doping,
gene therapy leaves no trace in blood or urine.
Gene therapy goes to the heart of an issue that will
turn our species upside down in the coming
decades. We are beginning to understand our own
operating system—genes—and we’re gaining the
ability to try to “improve” our genetic endowment.
Stem Cells: Promise, in Search of Results
By GINA KOLATA
Published August 24, 2004 New York Times
Boston—At three laboratories here, separated by a
taxi ride of no more than 10 or 15 minutes, the
world of stem cell research can be captured in all
its complexity, promise and diversity.
One of the labs focuses on cells taken from human embryos,
another on cells from mice and fish, and a third from stem
cells that mysteriously survived in the adult body long
after their original mission is over.
One idea…involves studying stem cells that are naturally
present in adults. Researchers have found such cells in a
variety of tissues and organs and say they seem to be part
of the body’s normal repair mechanism….the problem is
putting them to work to treat diseases. So far, no one has
succeeded.
The other line of research, with stem cells from
embryos, has a different obstacle. Although, in
theory, the cells could be coaxed into developing
into any of the body’s specialized cells, so far
scientists are still working on ways to direct their
growth in the laboratory and they have not yet
effectively cured diseases, even in animals.
…a few fetal cells enter a woman’s blood during
pregnancy and hoped to extract those cells for
prenatal diagnosis.
But then she discovered that the fetal cells do not
disappear when a pregnancy ends. Instead, they
remain in a woman’s body for decades, perhaps
indefinitely.
And if a woman’s tissues or organs are injured, fetal
cells from her baby migrate there, divide and turn
into the needed cell type, be it thyroid or liver,
intestine or gallbladder…
…find fetal cells by looking for male cells in tissues
and organs of women who have been pregnant
with boys (because it is easier to find and detect
male cells)
One woman, for example had hepatitis C, a viral
infection. But when her liver repaired itself, it used
cells that were not her own.
“Her entire liver was repopulated with male cells,”
Dr. Bianchi said.
Cell Cycle
Cell Cycle: The series of events from any stage in a
cell to the equivalent stage in a daughter cell.
Stages of the Cell Cycle
G1: Gap phase where the cell makes new protein,
lipid, etc., and basically goes on about its business.
S: Synthesis phase where DNA is replicated in
preparation for mitosis.
G2: Second gap phase where the cell prepares for
mitosis and takes care of business.
M: Mitosis, cell division.
Cell Structure
Why discuss cell structure??
During cell division, most of the cell structures must
be distributed to the newly formed cells.
Cell Structures
1. Centrioles and Spindle Fibers
These structures are necessary to move the
chromosomes during both mitosis and meiosis.
Cell Structures
2. Plasma Membrane
Surrounds the cell and protects it from the immediate
outer environment.
Actively regulates the movement of gases, nutrients,
signaling molecules and wastes into and out of the
cell.
Cell Structures
3. Cell Coat
Glycoprotein and polysaccharide covering over the
plasma membrane
Provides biochemical identity at the surface of the
cell
ABO antigens and histocompatibility antigens are
part of the cell coat.
Cell Structures
4. Nucleus
Surrounded by a membrane and contains the genetic
material.
In a non-dividing cell, DNA is uncoiled, dispersed
and called chromatin.
During mitosis and meiosis, DNA is condensed and
coiled into chromosomes.
Cell Structures
5. Nucleolus
An amorphous structure within the nucleus
composed of RNA and protein.
Center for the production of ribosomes
Cell Structures
6. Cytoplasm
Everything inside the cell except the nucleus
Includes all the intracellular structures or organelles
that do the work of the cell.
Highly compartmentalized by a membranous
structure called the endoplasmic reticulum (ER)
Ribosomes on the ER synthesize proteins from
genetic information
Cell Structures
7. Mitochondria
Membrane-bound organelles that synthesize large
amounts of the cellular energy compound ATP
(adenosine triphosphate)
Mitosis and Meiosis
Eukaryotic cells must undergo two processes:
1. Growth—cell division; each cell receives the
same amount and type of genetic material
2. Sexual Reproduction—Genetic material from
both male and female combine to make a new,
unique individual.
In both cases, preservation of the
correct number and distribution
of chromosomes is critical.
What are Mitosis and Meiosis?
 Mitosis: The division of somatic cells—cells of
the eukaryotic body that are not destined to
become sex cells.
A single mitosis event produces two of genetically
identical daughter cells from a single progenitor
cell.
Mitosis and Meiosis
http://cellsalive.com/mitosis.htm
Very cool interactive site
Mitosis
An example of mitosis:
Division of a fertilized egg cell to become a
multicellular organism composed of trillions of
cells.
Meiosis
Cell division that produces male and female gametes.
Meiosis is characterized by two division processes
that results in the formation of four gametes.
Meiosis
In animals, formation of gametes is called
gametogenesis
In plants, formation of gametes is called
sporogenesis
Fertilization occurs when male and female
gametes unite to form progeny.
Ploidy
The basic set of chromosomes or multiples of that
set.
Somatic cells are diploid and have a pair of each
chromosome (2n).
Gametes are haploid and have only one of each
chromosome (n).
Name
Genus species
# chromosomes (pr)
Human
Mouse
Cow
Dog
Guinea pig
Rat
Chicken
Homo sapiens
Mus musculus
Bos taurus
Canis familiaris
Cavia cobaya
Rattus norvegicus
Gallus domesticus
46 (23)
40 (20)
60 (30)
78 (39)
64 (32)
42 (21)
78 (39)
Mitosis
Interphase
Incorporates G1, S and G2 phases of the cell cycle
1. Active metabolic phase characterized by cell
growth
2. DNA is replicated such that each chromosome has
a duplicate, called sister chromatids that are
joined by a centromere.
Interphase
3. Centrioles are duplicated so there are now two
pairs
4. Spindle fibers are synthesized
Prophase
1. Chromosomes condense (shorten and thicken)
2. Nuclear membrane starts to disappear
3. Centriole pairs move to opposite sides of the cell
4. Mitotic spindle apparatus starts to appear,
composed of microtubules
Metaphase
1. Chromosomes (each composed of two "identical"
sister chromatids at this point) line up on the
metaphase plate
2. Each sister chromatid is attached to spindle fibers,
which are attached to the centrioles at opposite
poles
Anaphase
1. Centromeres split
2. Microtubules of the spindle fibers shorten and pull
the sister chromatids to opposite sides of the cells
Telophase
1. Spindle apparatus disappears
2. Nuclear envelope reforms
3. Chromosomes decondense--get longer
4. Cytokenesis (cell division) takes place by
structural fibers constricting the cell between the
two nuclei.