Mol Smith

We seem to be living in an age where sexual identity has become confused in the young generation. I have no doubt that there are genuine cases both born out of either physchological issues, or growing up in a social system where everything is being questioned down to a miniscule level. And then there are the more scientific or biological issues where a baby is born with both sets of sexual organs complete: male & female. In these cases, what does a doctor, or surgeon do to determine the sexual identity of the new born person? This is where microscopy comes in! It might be interesting to discover what the deciding factor is as it comes down to genetics: the machinery of creating life.

From wikipedia:
They look to see if the baby's cell contains Barr Bodies. A genotypical human female has only one Barr body per somatic cell, while a genotypical human male has none.
 The Barr body was named after its discoverer Murray Barr.
Murray Llewellyn Barr OC FRSC FRS (June 20, 1908 – May 4, 1995) was a (Canadian physician.)

It's the inactive X chromosome in a
female somatic cell, rendered inactive in a process called lyonization. These use a swab to wipe loose cells from inside the baby's cheeks, and then identify which sex the new born is by the presence of the Y  or W chromosome rather than the diploidy of the X in the cells. The Lyon hypothesis states that in cells with multiple X chromosomes, all but one are inactivated during mammalian embryogenesis. This happens early in embryonic development at random humans, except in some extra-embryonic tissues in which the father's X chromosome is always deactivated. In humans with more than one X chromosome, the number of Barr bodies visible at interphase is always one fewer than the total number of X chromosomes. Barr bodies can be seen in the nucleus of neutrophils, at the rim of the nucleus in female somatic cells between divisions.

Somatic cells are any cell in the body that are not gametes (sperm or egg), germ cells (cells that go on to become gametes), or stem cells. Essentially, all cells that make up an organism’s body and are not used to directly form a new organism during reproduction are somatic cells. The word somatic comes from the Greek word σὠμα (soma), which means body. In the human body, there are about 220 types of somatic cells.

There are many different kinds of somatic cells in the human body because nearly every cell found inside and on the surface of the human body, with the exception of cells that become sperm and eggs, is a somatic cell. In addition, mammals have many organ systems that specialize in specific functions, so there are many different specialized cells.

Cheek Cells are  epithelial cells serve a similar function to all epithelium, which is as a lining and barrier separating the underlying tissues from the body's cavities and the external world.  These cells also secrete mucus that adds protection, lubrication and a barrier against drying out. Some epithelial cells have secretory, gas and nutrient transport, absorptive functions or mechanical movement facilitated by cilia. But the simple squamous epithelium is primarily a barrier to infection.

Look at you own cheek cells?
Use a cotton bud to swab the inside of your cheek. Place the swab  onto the middle of a glass microscope slide. Add a single droplet of water squeezed from a plastic pipette onto the centre of the slide. Rotate the swab in the water to release the human cheek cells into the drop of water. Next, add one drop of methylene blue to the water and cell solution to stain the cheek cells. This will allow you to more easily see them during observation. If methylene blue cannot be used or obtained, a drop of iodine can be used as a substitute. Once the cells have been stained, position a cover slip at a 45 degree angle just inside the left edge of the solution. Move your fingers down and to the right to place the cover slip over the cheek cell solution. You can now view the cells under the microscope using x40 or x100 magnification.

Note: various stains (dyes) are used in microscopy to help observe structures which would otherwise be transparent or more difficult to differentiate. For a list of stains and their uses, see this wikipedia article:


Human Cheek Cells - stained

 Wiki  common by Dietzel65, Steffen Dietzel [CC BY-SA]

Nucleus of a female amniotic fluid cell. Top: Both X-chromosome territories are detected by FISH. Shown is a single optical section made with a confocal microscope. Bottom: Same nucleus stained with DAPI and recorded with a CCD camera. The Barr body is indicated by the arrow, it identifies the inactive X (Xi).

Cheek cells stained with iodine