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Welcome to The Visible Embryo, a comprehensive educational resource on human development from conception to birth.

The Visible Embryo provides visual references for changes in fetal development throughout pregnancy and can be navigated via fetal development or maternal changes.

The National Institutes of Child Health and Human Development awarded Phase I and Phase II Small Business Innovative Research Grants to develop The Visible Embryo. Initally designed to evaluate the internet as a teaching tool for first year medical students, The Visible Embryo is linked to over 600 educational institutions and is viewed by more than ' million visitors each month.


WHO International Clinical Trials Registry Platform
The World Health Organization (WHO) has created a new Web site to help researchers, doctors and patients obtain reliable information on high-quality clinical trials. Now you can go to one website and search all registers to identify clinical trial research underway around the world!



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Disclaimer: The Visible Embryo web site is provided for your general information only. The information contained on this site should not be treated as a substitute for medical, legal or other professional advice. Neither is The Visible Embryo responsible or liable for the contents of any websites of third parties which are listed on this site.
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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
Click weeks 0 - 40 and follow fetal growth
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May 20, 2011--------News Archive

New Complexity In Genetic Diversity Of RNA
It turns out
RNA proteins do not precisely match the genes that encode them.

Validating Preschool Programs For Autism
Scientists from the Universities of Miami, North Carolina and Colorado, developed measures to evaluate teaching programs for autistic preschool children.


May 19, 2011--------News Archive

New Technique To 'Lift The Hood’ On Autism
A new study provides compelling evidence that exome-sequencing is an effective way to discover which of the 20,000 and more genes in the human genome are responsible for autism spectrum disorders.

Maternal Smoking Causes Changes In Fetal DNA
Children whose mothers or grandmothers smoked during pregnancy are at increased risk of asthma in childhood. A new study indicates changes in DNA methylation occuring before birth may be the root cause.


May 18, 2011--------News Archive

New Antiepileptic Drugs Don't Increase Birth Defects
Use of newer-generation antiepileptic drugs prescribed for bipolar mood disorders and migraine headaches, during the first trimester of pregnancy, are not associated with an increased risk of major birth defects in the first year of life in Denmark.

Neglect And Deprevation Age a Child's Chromosomes
Study of institutionalized Romanian children finds prematurely shortened telomeres, a mark of cell aging.


May 17, 2011--------News Archive

Older Fathers Linked to Autism In Children
Researchers sequenced protein-coding sections of affected childrens' genomes and their findings support population studies showing that autism is more common among children of older parents, especially older fathers.

Gene Variation Linked to Infertility in Women
A variation in a gene involved in regulating cholesterol also appears to affect progesterone in women, making it a likely culprit in cases of infertility.


May 16, 2011--------News Archive

Genetic Clue to Common Birth Defects Found
Scientists at King’s College London have for the first time uncovered a gene responsible for Adams-Oliver Syndrome, giving valuable insight into the possible genetic causes of common birth defects found in the wider population.

'Master switch' For Obesity and Diabetes Discovered
A gene linked to type 2 diabetes and cholesterol levels is in fact a 'master regulator' gene, which controls other genes found within fat in the body.

Tiny Change in One Gene May Explain Human Brain
The deep fissures and convolutions that increase the surface area and allow for rational and abstract thoughts of the human brain may be due to the LAMC3 gene.

Gene Change Can Get You Cancer Or Normal Growth
The deep fissures and convolutions that increase the surface area and allow for rational and abstract thoughts of the human brain may be due to one gene.


WHO Child Growth Charts

A detailed comparison of DNA and RNA in human cells has uncovered a surprising number of cases where the corresponding sequences are not, as has long been assumed, identical.

The RNA-DNA differences generate proteins that do not precisely match the genes that encode them.

The finding, published May 19, 2011, in Science Express, suggests that unknown cellular processes are acting on RNA to generate a sequence that is not an exact replica of the DNA from which it is copied. Vivian Cheung, the Howard Hughes Medical Institute investigator who led the study, says the RNA-DNA differences, which were found in the 27 individuals whose genetic sequences were analyzed, are a previously unrecognized source of genetic diversity that should be taken into account in future studies.

Genes have long been considered the genetic blueprints for all of the proteins in a cell. To produce a protein, a gene's DNA sequence is copied, or transcribed, into RNA. That RNA copy specifies which amino acids will be strung together to build the corresponding protein.

"The idea that RNA and protein sequences are nearly identical to the corresponding DNA sequences is strongly held and has not been questioned in the past," says Cheung, whose lab is at the University of Pennsylvania School of Medicine.

With recent advances in sequencing technology, however, it has become possible to perform the kind of analysis necessary to test that assumption. In their study, Cheung and her colleagues compared the sequences of DNA and RNA in B cells (a type of white blood cell) from 27 individuals. The DNA sequences they analyzed came from large, ongoing genomics projects, the International HapMap Project and the 1000 Genomes Project. They used high-throughput sequencing technology to sequence the RNA of B cells from the same individuals.

Within the sequences' protein-coding segments, they found 10,210 sites where RNA sequences were not the same as the corresponding DNA. They call these sites RNA-DNA differences, or RDDs.

They found at least one RDD site in about 40 percent of genes, and many of these RDDs cause the cell to produce different protein sequences than would be expected based on the DNA. In the cells they studied, the sequences of thousands of proteins may be different from their corresponding DNA, the scientists say.

"It is important to note that since these RDDs were found with just 27 individuals, they are common," Cheung points out.

To test whether the phenomenon was specific to B cells, the team also searched for RDDs in DNA and RNA sequences in human skin and brain cells. They found that most of the RDD sites occurred in at least some samples of all three cell types and were present in cells from both infants and adults, indicating that the RNA-DNA differences are not due to aging or specific to certain developmental stages.

Cheung says the particular RNA-DNA discrepancies they found appear systematic. There are four bases, or letters, that make up the DNA code: A, T, G, and C. The RNA equivalents are A, U, G, and C. In individuals who had RNA-DNA differences at a specific site in the genome, the mismatched bases were always the same.

In other words, if the team found a C in the RNA sequence where they expected an A, all individuals who had an RDD at this point also had a C in their RNA sequence—never a G or a U.

"Such uniformity makes us believe that there is a 'code' or 'guide' that mediates the RDDs and they are not random events," Cheung explains.

In the 1980s, scientists found the first examples of RNA sequences that did not match the corresponding DNA. Today, many genes in humans and other organisms are now known to be targets of RNA editing. The known examples of such editing are mediated by enzymes called deaminases, which chemically modify specific As and Cs in the RNA sequence, converting the As to Gs and the Cs to Us.

Cheung says abnormal RNA editing of glutamate and serotonin receptors has been associated with psychiatric disorders and resistance to certain drugs–evidence that traditional RNA editing is critical for maintaining normal cellular function.

Nearly half of the RDDs uncovered in the new study cannot be explained by the activity of deaminase enzymes, however, indicating that unknown processes must be modifying the RNA sequence, either during or after transcription.

Cheung says there are several possibilities. For example, the DNA might be chemically or structurally modified so that certain bases look different to the enzyme that copies DNA to RNA, causing it to insert a mismatched RNA base during transcription.

Alternatively, newly synthesized RNAs might be folded in such a way to signal enzymes to convert certain bases to other ones. The biological significance of these modifications remains to be determined, but since they are widespread among individuals and cell types, Cheung and her colleagues expect they have some function.

Although all of the individuals analyzed in the study had a large number of RDDs, there was a great deal of variability in the specific RDDs found in each person's genetic material. This variability likely contributes to differences in disease susceptibility, Cheung says. Scientists have generally searched for DNA sequence differences to explain why some people are more prone to certain diseases, whereas studies of RNA and proteins have considered levels of expression, but not sequences.

But major genetic contributors for many diseases remain unknown, and Cheung says it will be valuable to begin to include RNA sequences in disease-association studies.

Cheung notes that her team's analysis would not have been possible without the large-scale genomics projects, which until now have focused on DNA.

"Without these large-scale genome projects, we would not have the volume of DNA sequences for comparisons and would not have the technologies that enabled us to sequence our RNA samples," she says.

"Our study provides support for why large-scale data are important. Previously the focus was on DNA, now our results suggest that RNA sequences also need to be examined. Exploration of these data, when founded on fundamental biology, will lead to fruitful scientific discoveries."