Egg Cells from Skin Cells?

     In this article, scientists are working to create a human egg from an adult cell. They used a technique that combines cloning with fertilization, along with a small amount of chemical coaxing. Researchers had succeeded in producing egg cells of many other types of animals, so the hunt to produce egg and sperm of humans has been on.

    An attempt was made when the nucleus from a human egg cell was taken out and replaced with the nucleus of a skin cell, which is called somatic cell nuclear transfer. In this case, the researchers weren't trying to clone a human, but wanted to make an egg cell, which is half of the DNA of a skin cell. When done on mice, once the cloned egg was fertilized, it removed half of its chromosomes in order to take in the chromosomes of the sperm. In human eggs, this did not happen, so the researchers added roscovitine to persuade the egg to allow the chromosomes to be removed. This led to no viable eggs, since many would kick out the wrong half of chromosomes or end up with an incorrect number of chromosomes. It is theorized that it's due to the chromosomes pairing up randomly instead of with their specific other half, like in normal meiosis.

    This is still being tested in Japan, and hopefully, these trials are getting us a step closer to creating viable eggs. I think this is such an interesting idea that can help many people who would like biological children, but have reasons they wouldn't be able to. The fact that similar tests have been proven possible in other animals makes me optimistic about the probability of this becoming an option in the future.

Charlotte the Stingray to have a "virgin birth."

 Charlotte, who is a round stingray living at an aquarium in Hendersonville, North Carolina, went viral when it was learned that she was pregnant.  This was huge news because she's been living without a male tankmate for nearly 8 years at this point.  A rumor had gone around suggesting Charlotte had mated with one of the male sharks in the tank, but the aquarium dismissed this.  What has happened is that Charlotte has undergone parthenogenesis, a process that can occur in a few select animal species.  Parthenogenesis is a form of asexual reproduction, where offspring are produced without a male providing sperm.  In the article , one of the aquarium workers states that the offspring won't be identical clones to the mother.  The egg will have fused into a polar body that develops into an embryo.  As of today, no articles have come out confirming Charlotte has given birth to her pups.

This story is very interesting, because it brought attention to something that a lot of people don't know about it, which is parthenogenesis.  Many of my family and friends found it absolutely wild that a stingray could be pregnant without a male mate.  I was shocked reading that Charlotte's parthenogenesis was not her cloning herself, because I've been told that's exactly what parthenogenesis is.  There are apparently two forms of the process, one where the egg fuses into a polar body and develops into the embryo like in this case.  And the other case is where the gametocyte skips meiosis and undergoes mitosis, producing a genetically identical embryo to the mother.  I hope to hear about Charlotte's pregnancy going well because this may be the first recorded case of parthenogenesis in the round ray species.

Article Link: https://apnews.com/article/stingray-pregnant-charlotte-north-carolina-1da7d7ab06bf22169ef2c8e589db9cb4?utm_source=copy&utm_medium=share

Parthenogenesis article: https://www.sciencedirect.com/topics/veterinary-science-and-veterinary-medicine/parthenogenesis

Chromosomal Gene Analysis of Cephalopods Give Scientists a Sneak Peek Into the Their Evolution

 

A Cephalopods nervous system is about as weird as the creatures’ external features. The evolutionary pathway that led to this infinitely complex nervous system has long been cloudy and less understood than other aquatic species. Recently, chromosomal assemblies of three cephalopod species – two squids  know as Doryteuthis pealeii and Euprymna scolopes along with an octopus species known as Octopus bimaculoides – have allowed scientists to better recognize which specific genes are present and in what order. This newfound knowledge can allow geneticists to further study components within the genome that are driving the expression of these genes (Nature).

Cephalopod genomes are notably different than those found in humans. Genomes within the two species of squid were found to be about 1.5 times larger than that of humans. While the Octopus’ genes more closely resemble a humans at about 90% size. Furthermore, it is found that while humans evolved through meiosis, a process in which two rounds of genome duplication occurs, a cephalopods evolution does not involve whole genome duplication, but instead undergoes “immense genome rearrangements” according to a Science Daily article. Which makes sense given that cephalopods started evolving 300 million years before humans existed. Discovery of this difference in duplication is a foot forward in finding out how these complex and highly intelligent creatures have evolved and thrived.

Plants Show Inverse of Meiotic Phases

Gabriela Cabral and Peter Schlögelhofer at the Max F. Perutz Laboratories (MFPL) of the University of Vienna and the Medical University of Vienna have studied the process of meiosis in specific plant species, and found evidence that some of them carry out the inverse of the usual sequence of meiotic phases. They provide the first in-depth analysis of their meiotic behavior.

This was discovered to happen in Rhynchospora pubera (pictured above) and R. tenuis, plants native to Brazil, which were initially what Cabral studied, but then moved on to study C. elegans, a nematode worm.  She found that all three organisms have something in common:  they all have the same chromosome type present in them. Their holocentric chromosomes have the property of, during somatic cell divisions, attaching spindle microtubules along their entire length, unlike in humans where the microtubules attach to a specific site known as the kinetochore.

This property means that holocentric chromosomes have problems during meiosis that monocentric chromosomes do not face, so in order to distribute the chromosomes correctly they have inversed the usual meiotic sequence. The sister chromatids are separated during the first meiotic division. Prior to the second meiotic division, the homologous non-sister chromatids are associated with thin chromatin threads, and this allows for proper orientation and disjunction during the second division.

I think that it is very interesting how some species of plants have completely changed the steps of meiosis I and II, but yet come out with the same result, if not better. I wonder if these plants have only recently developed this process of inverse meiosis, or if this is a process much older than what we think is “normal” meiosis.

Link to article: http://www.sciencedaily.com/releases/2014/10/141029124555.htm