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Today, The Visible Embryo is linked to over 600 educational institutions and is viewed by more than 1 million visitors each month. The field of early embryology has grown to include the identification of the stem cell as not only critical to organogenesis in the embryo, but equally critical to organ function and repair in the adult human. The identification and understanding of genetic malfunction, inflammatory responses, and the progression in chronic disease, begins with a grounding in primary cellular and systemic functions manifested in the study of the early embryo.

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Pregnancy Timeline by SemestersFetal liver is producing blood cellsHead may position into pelvisBrain convolutions beginFull TermWhite fat begins to be madeWhite fat begins to be madeHead may position into pelvisImmune system beginningImmune system beginningPeriod of rapid brain growthBrain convolutions beginLungs begin to produce surfactantSensory brain waves begin to activateSensory brain waves begin to activateInner Ear Bones HardenBone marrow starts making blood cellsBone marrow starts making blood cellsBrown fat surrounds lymphatic systemFetal sexual organs visibleFinger and toe prints appearFinger and toe prints appearHeartbeat can be detectedHeartbeat can be detectedBasic Brain Structure in PlaceThe Appearance of SomitesFirst Detectable Brain WavesA Four Chambered HeartBeginning Cerebral HemispheresFemale Reproductive SystemEnd of Embryonic PeriodEnd of Embryonic PeriodFirst Thin Layer of Skin AppearsThird TrimesterSecond TrimesterFirst TrimesterFertilizationDevelopmental Timeline
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April 23, 2013--------News Archive

 
Drosophila melanogaster
Insect bodies are generally covered with a large number of microscopic hairs.
This is the case for the legs of many closely related species of the fruit fly genus
Drosophila, although the animals have a bald patch on the second pair of legs,
intriguingly known as the naked valley.





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Surprising new function for small RNAs in evolution

An international research team has discovered a completely new mechanism by which evolution can change the appearance of an organism.

The research team found that the number of hairs on flies’ legs varies according to the level of activity of a so-called microRNA. The results, published in the journal Current Biology, shed a completely new light on the molecular mechanisms of evolution.


It has long been known that certain proteins, known as transcription factors, directly control the way in which information is read from DNA. As a result, it is widely believed that changes in genes encoding such proteins underlie the mechanisms responsible for evolutionary adaptation.

The idea that small RNA molecules, so-called microRNAs, may play an important part in evolutionary changes to animals’ appearance is completely new.


An international team of researchers, including Christian Schlötterer and Alistair McGregor from the Institute of Population Genetics of the University of Veterinary Medicine, Vienna (Vetmeduni Vienna), has now published a study that describes such an evolutionary mechanism.

Small and large bald patches

Insect bodies are generally covered with a large number of microscopic hairs. This is the case for the legs of many closely related species of the fruit fly genus Drosophila, although the animals have a bald patch on the second pair of legs, intriguingly known as the naked valley.

Previous work had shown that the size of this patch is regulated by the gene ultrabithorax (Ubx) and that it differs between species. However, the work at the Vetmeduni Vienna showed that similar differences are shown by individuals from different populations of Drosophila melanogaster.

Their search for the genetic basis of the variation led the researchers to a segment of fruit fly DNA that contained four genes. Three of these genes were known to encode proteins with no role in the development of the hairs. The fourth gene, known as miR-92a, encodes a microRNA. Previous experiments had shown that an increase in activity of the miR-92a gene was associated with a loss of hairs from the animals’ wings. By overexpressing the gene in the legs of the fruit flies, the scientists were able to cause hair loss on the animals’ legs.


Schlötterer is naturally excited by the findings.

“This is the first experiment to show that natural variation in the expression of a microRNA can lead to a change in the appearance of an organism.

MicroRNAs can fine-tune the level at which genes are expressed, so evolutionary changes in the production of microRNA would be an elegant way to cause morphological changes.”


The article “Evolution of mir-92a Underlies Natural Morphological Variation in Drosophila melanogaster” by Saad Arif, Sophie Murat, Isabel Almudi, Maria D.S. Nunes, Diane Bortolamiol-Becet, Naomi S. McGregor, James M.S. Currie, Harri Hughes, Matthew Ronshaugen, Élio Sucena, Eric C. Lai, Christian Schlötterer and Alistair P. McGregor appeared in the journal “Current Biology” (23(6), pp.523-528).

The same issue of Current Biology (23(6) includes on pp. R247-R249 a commentary on the article by Artyom Kopp (Department of Ecology and Evolution, University of California Davis, USA) under the title “Evolutionary Genetics: Big Effect of a Small RNA”.

Original article: http://www.vetmeduni.ac.at/en/infoservice/current-issues/presseinformation/presseinfo2013/press-release-04-19-2013-a-surprising-new-function-for-small-rnas-in-evolution/