AP Biology class blog for discussing current research in Biology

Author: metabolizm

A New Kind of DNA

Scientists at the Garvan Institute of Medical Research in Australia have discovered a new form of DNA in our cells. They’ve found that this DNA does not look the same as the traditional double-helix we are all familiar with, but instead is in the shape of a four stranded “knot”. This new DNA is called i-motif. Scientists not only know the shape of this new type of DNA, they also know how it differs from helical DNA and where it is located. Unlike helical DNA in which the Cs and Gs bind, the Cs on the same strand in the i-motif bind together.


In order to locate the i-motifs in the cells, researchers developed a new tool than can recognize this type of DNA. This tool is a fragment of an antibody that attaches to the i-motif DNA molecule. They used fluorescence techniques to find exactly where in the nucleus of human cells the i-motif DNA was.

Scientists also have concluded that the i-motifs most likely form at the late G1 phase. They appear in the telomere and promoter regions.


CRISPR/Cas9 System undoing genetic disease? Maybe!

A recent study released from the Whitehead Institute for Biomedical Research discuss the pioneering way scientists are using CRISPR technology to help boys born with Fragile X syndrome.

Fragile X syndrome is a rare condition affecting 1 out of 3600 boys born. Symptoms of this genetic condition are delayed development, often impulsive actions and intellectual difficulties. There is no cure. The disease is caused by DNA methylation, which is caused by the random addition of a methyl (CH3) group to the DNA strand. CRISPR technology has made it possible for this methylation to be removed – essentially, the CRISPR/Cas9 system removes the extra CH3 group.


The mutation occurs in the FMR1 gene on the X chromosome, as the name suggests. The methylation prevents the expression of the FMR1 gene, and the CRISPR/Cas9 system removes the added CH3 group, allowing the gene to be expressed. The FMR1 gene is crucial in brain and cognitive development, so the CRISPR technology allows for this gene to function – virtually rescuing the person from the disease.

Due to the successful application of CRISPR technology to Fragile X syndrome and the FMR1 gene, this rare disease is better understood by scientists. This same technology, which removes the added CH3 group, thus removing the methylation, is hypothesized to be useful in lessening or eliminating symptoms from diseases such as muscular dystrophy.

Whole-Grain Bread: The Healthy Choice…or is it?

Contrary to popular belief, whole-grain bread might not be healthier for everyone. A new study has determined that whether white bread or whole-grain bread is healthier for you depends on the microbes in your gut. After studying 20 people for one week each, researchers found that some people’s blood sugar levels raised after eating standard white bread while others did not. Similarly, they found that some people’s blood sugar rose when eating standard whole grain bread. The researchers, Eran Elinav and Eran Segal, studied the mix of microbes in the stool samples as well as their genetic makeup.

This study is part of a growing group of studies that support personalized nutrition that is customized to your genetic makeup rather than a plan for everyone. The same group has also done other research in the nutrition field in Israel, where they studied how people respond to eating certain foods.

Questioning one of the most widely-held beliefs about the origins of life!

Two scientists, Dr. Charles Carter, of University of North Carolina at Chapel Hill, and Peter Wills, a physics professor at the University of Auckland, are challenging one of the most widely-held beliefs in the world of science.

A widely accepted hypothesis of the origin of life is called the “RNA-world” hypothesis, which states that life began from nucleic acids and only evolved later into proteins. However, in two recent studies, scientists Carter and Wills have found that this hypothesis is false, and have named their findings the “peptide-RNA” hypothesis. They believe their findings are much more probable and realistic. They argue that RNA could not be the source of biological life on earth because it lacks an important characteristic, called “reflexivity”. This means RNA lacks the ability to form the feedback loop that is necessary to lead to eventual life forms.


At the core of their “peptide-RNA” hypothesis is that the remnants of ancient enzymes are still found in all living organisms today. These ancient enzymes are called aminoacyl-tRNA-synthetases (aaRSs). These 20 aaRSs enzymes are broken into 2 structurally distinct families which each are exact opposites of each other. Being that these enzymes are so simple in structure, Cater and Wills believe they are the basis of biological life.

So, which theory do you believe, the “RNA-world” hypothesis or the “peptide-RNA” hypothesis?

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Worried about BPA in your water? Don’t be.

Life developed on Earth because of its rare abundance of water. While we do need water to survive, our water must also be clean and potable, without contaminants or other substances. Recently, the US Geological Survey (USGS) and the US Environmental Protection Agency (EPA) have conducted surveys on our drinking water. The USGS-EPA study has brought to light the disproportionate representation in the media of the toxicity of BPA in drinking water. BPA, or bisphenol A, is used to make epoxy resin and polycarbonate plastic, which is commonly used to make plastic water bottles. BPA in drinking water is commonly covered in the media, even though it was only found in less than 40% of the streams tested in the USGS-EPA study. Contrary to what most people believe, an adult would have to drink over 5,600 gallons of water in one day to reach the safe intake level for BPA set by the EPA. BPA is estrogenic, which means it contains estrone, a toxic estrogen that is naturally produced in the human body. Therefore, concerns of BPA’s toxicity in our drinking water are not nearly as imminent as many people believe.


So, what should we be worried about in our water? The USGS-EPA study found that all streams tested contained at least one toxin. The organizations tested 38 streams and searched for 719 substances. Some streams contained only one substance, yet others contained 162. 66-84% of the toxins found in the streams were results of human activity. Though the USGS and EPA found these toxins, the toxicity of these toxins must be taken into account. This new data sheds light on our drinking water, and takes the spotlight off of BPA.


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