Genetics in the News

New York Times, August 25 2004

The Website

THE WEBSITE IS NOT CURRENT AS OF AUGUST 26, 2004!!

http://ag.arizona.edu/classes/ans213/

I PROMISE TO INFORM YOU WHEN IT IS UP

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 ResultsBy 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 Membrane2. 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 Coat3. Cell CoatGlycoprotein 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. Nucleus4. NucleusSurrounded by a membrane and contains the genetic

material.

In a non-dividing cell, DNA is uncoiled, dispersed and called chromatin.chromatin.

During mitosis and meiosis, DNA is condensed and coiled into chromosomeschromosomes..

             

Cell Structures

5. Nucleolus5. Nucleolus

An amorphous structure within the nucleus composed of RNA and protein.

Center for the production of ribosomes

Cell Structures

6. Cytoplasm6. CytoplasmEverything 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)endoplasmic reticulum (ER)RibosomesRibosomes on the ER synthesize proteins from

genetic information

Cell Structures

7. Mitochondria7. 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: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 gametogenesisgametogenesis

In plants, formation of gametes is called sporogenesissporogenesis

FertilizationFertilization 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 diploid and have a pair of each chromosome (2n).

Gametes are haploidhaploid and have only one of each chromosome (n).

Name Genus species # chromosomes (pr)

Human Homo sapiens 46 (23)Mouse Mus musculus 40 (20)Cow Bos taurus 60 (30)Dog Canis familiaris 78 (39)Guinea pig Cavia cobaya 64 (32)Rat Rattus norvegicus 42 (21)Chicken Gallus domesticus 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 sister chromatids that are joined by a centromerecentromere..

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. CytokenesisCytokenesis (cell division) takes place by structural fibers constricting the cell between the two nuclei.