Health Editor’s Note: This amazing medical article is about the process of meiosis and how now it can be viewed in all its intricacies. Meiosis is a form of cell division. I am going to take you back to the very simplified ground work for how our bodies make new cells. New cells result from a division (reproduction) of a cell. During the process of cell development for mitosis, the DNA is doubled so each of the two cells that arise from a cell have the exact same DNA knowledge. Mitosis produces diploid cells which have two complete sets of DNA. Cells divide by mitosis to replace damaged, old, or dead cells. Cells also divide so growth can occur. In the human body nearly two trillion cells divide each day. There are 23 pairs of chromosomes per cell or 46 chromosomes.
Meiosis is the process that a cell (haploid) goes through to halve the number of chromosomes. Meiosis occurs in only egg and sperm cells. This is necessary for egg and sperm cells which combine to form the normal number of chromosomes (46) per cell. 23 plus 23 are just right. Thus the zygote or fertilized egg has 46 chromosomes.
Our bodies use both meiosis and mitosis to produce cells. Generally if there is a disruption in the process of meiosis, this will lead to developmental disorders for the egg as well as being the cause of most miscarriages ….Carol
Zooming in on Meiosis
by Dr. Francis Collins/ National Institute of Health Director’s Blog
Meiosis—the formation of egg and sperm cells—is a highly choreographed process that creates genetic diversity in all plants and animals, including humans, to make each of us unique. This kaleidoscopic image shows cells from a worm exchanging DNA during meiosis.
You can see a protein-based polymer tether (green) from what’s called the synaptonemal complex. The complex holds together partner chromosomes (magenta) to facilitate DNA exchange in nuclei (white). Moving from left to right are views of the molecular assembly that progressively zoom in on the DNA, revealing in exquisite detail (far right) the two paired partner chromosomes perfectly aligned. This is not just the familiar DNA double helix. This is a double helix made up of two double helices!
The image, one of the winners of the Biophysical Society’s 2018 Art of Science Image Contest, comes from the NIH-supported lab of Abby Dernburg at the University of California, Berkeley. To capture this award winner, Simone Köhler, then a postdoc in the lab, used two super-resolution imaging techniques: photo-activated localization microscopy (PALM) and stochastic optical reconstruction microscopy (STORM).
These breakthrough approaches create a very high-resolution image that records the position of individual proteins within a cell. Working in collaboration with the lab of Ke Xu, also at UC Berkeley, Köhler combined both methods to map out the molecular architecture of the synaptonemal complex, as well as to see how it changes during the process of DNA exchange [1].
All photographic beauty aside, this work and other projects in the Dernburg Lab have led to a surprising result: the synaptonemal complex behaves as a liquid crystal, an intermediate phase of matter in which molecules have a regular organization but can move freely [2]. This unique material assembles between paired chromosomes as they interact and holds them at a fixed distance. More amazingly, the results suggest that the synaptonemal complex acts as a “highway” for biochemical signals to travel rapidly along chromosomes. Thus, this information flow controls both the spacing and the number of DNA exchanges between paired chromosomes.
This work on the dynamics of chromosome-chromosome interactions is a great example of the value of basic research. Errors in meiosis are the leading known cause of miscarriage and a frequent cause of developmental disabilities. But seeing meiosis at this super resolution also conveys a sense of awe at how this life-giving process contributes to making us all unique.
References:
[1] Superresolution microscopy reveals the three-dimensional organization of meiotic chromosome axes in intactCaenorhabditis elegans tissue. Köhler S, Wojcik M, Xu K, Dernburg AF.. Proc Natl Acad Sci U S A. 2017 Jun 13;114(24):E4734-E4743.
[2] The synaptonemal complex has liquid crystalline properties and spatially regulates meiotic recombination factors. Rog O, Köhler S, Dernburg AF. Elife. 2017 Jan 3;6. pii: e21455.
Carol graduated from Riverside White Cross School of Nursing in Columbus, Ohio and received her diploma as a registered nurse. She attended Bowling Green State University where she received a Bachelor of Arts Degree in History and Literature. She attended the University of Toledo, College of Nursing, and received a Master’s of Nursing Science Degree as an Educator.
She has traveled extensively, is a photographer, and writes on medical issues. Carol has three children RJ, Katherine, and Stephen – one daughter-in-law; Katie – two granddaughters; Isabella Marianna and Zoe Olivia – and one grandson, Alexander Paul. She also shares her life with her husband Gordon Duff, many cats, and two rescues.
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