AP Biology class blog for discussing current research in Biology

Author: paxian

i-motif: A new form of DNA discovered

Australian researchers have discovered a new structure of DNA called i-motif. This form of DNA is in the shape of a twisted knot, vastly different from the conventional double helix model. i-motif basically looks like a four-stranded knot of DNA. In the i-motif form, the C bases on the same strand of DNA bind to each other instead of their complementary pairs.


(Photo: Wikimedia Commons)

How did scientists discover i-motif?

i-motif previously haven’t been seen before, apart from in in-vitro (which means under laboratory conditions and not in the natural world) To detect i-motif, scientists used a tool made up of a fragment of an antibody molecule. This antibody could recognize and attach to i-motifs. Researchers showed that the i-motif structures mostly formed at the G1 phase -when mRNA is synthesized- in a cells life cycle. The i-motifs show up in promoter regions and in telomeres in the chromosome.

While scientists aren’t really sure the actual reason for their existence, some researchers suggest that they are there to help switch genes on and off and affect whether or not a gene is actively read.

Whatever the reason for their existence, they have potential to play an important role in how and when DNA is read. Prof Marcel Dinger at the Garvan Institute for Medical Research says, “It’s exciting to uncover a whole new form of DNA in cells — and these findings will set the stage for a whole new push to understand what this new DNA shape is really for, and whether it will impact on health and disease.”

Closer to Reality: Gene Editing Technology

In August of 2017, scientists in the United States were successful in genetically modifying human embryos, becoming the first to use CRISPR-cas9 to fix a disease causing DNA replication error in early stage human embryos. This latest test was the largest scale to take place and proved that scientists were able to correct a mutation that caused a genetic heart condition called hypertrophic cardiomyopathy.

CRISPR-cas9 is a genome editing tool that is faster and more economical than othe r DNA editing techniques. CRISPR-cas9 consists of two molecules, an enzyme called cas9 cuts strands of DNA so pieces of DNA can be inserted in specific areas. RNA called gRNA or guide RNA guide the cas9 enzyme to the locations where impacted regions will be edited.

(Source: Wikipedia Commons)


Further tests following the first large-scale embryo trial will attempt to solidify CRISPR’s track record and bring it closer to clinical trials. During the clinical trials, scientists would use humans- implanting the modified embryos in volunteers and tracking births and progress of the children.

Gene editing has not emerged without controversy. While many argue that this technology can be used to engineer the human race to create genetically enhanced future generations, it cannot be overlooked that CRISPR technology is fundamentally for helping to repair genetic defects before birth. While genetic discrimination and homogeneity are possible risks, the rewards from the eradication of many genetic disorders are too important to dismiss gene editing technology from existing.


Bacteria may be more complex than we think

Photo by Wikimedia Commons

A common public misconception is that bacteria live alone and act as solitary organisms. This misconception, however, is far from reality.

Bacteria always live in very dense communities. Most bacteria prefer to live in a biofilm, a name for a group of organisms that stick together on a surface in an aqueous environment. The cells that stick together form an extracellular matrix which provides structural and biochemical support to the surrounding cells. In these biofilms, bacteria increase efficiency by dividing labor. The exterior cells in the biofilm defend the group from threats while the interior cells produce food for the rest.

While it has long been known that bacteria can communicate through the group with chemical signals, also known as quorum sensing, new studies show that bacteria can also communicate with one another electrically. Ned Wingreen, a biophysicist at Princeton describes the significance of the discovery; “I think these are arguably the most important developments in microbiology in the last couple years, We’re learning about an entirely new mode of communication.”

An entirely new mode of communication it is! Heres how it works:

Ion channels in a bacteria cell’s outer membrane allow electrically charged molecules to pass in and out, just like a neuron or nerve cell. Neurons pump out Sodium ions and let in Potassium ions until the threshold is reached and depolarization occurs. This is known as an action potential. Gurol Suel, a biophysicist at UCSD emphasizes that while the bacteria’s electrical impulse is similar to a neuron’s, it is much slower, a few millimeters per hour compared to a neuron’s 100 meters per second.

Photo by Chris 73 Wikimedia Commons

So what does this research mean?

Scientists agree that this revelation could open new doors to discovery. Suel says that electrical signaling has been shown to be stronger than traditional chemical signaling. In his research, Suel found that potassium signals could travel at constant strength for 1000 times the width of a bacteria cell, much longer and stronger than any chemical signal. Electrical signaling could also mean more communication between different bacteria. Traditional chemical signaling relies on receptors to receive messages, while bacteria, plant cells, and animal neurons all use potassium to send and receive signals. If these findings are correct, there’s potential in the future for the development of new antibiotics.

Learning about electrical signaling in bacteria has complicated our understanding of these previously thought to be simple organisms. El Naggar, another biophysicist at USC says, “Now we’re thinking of [bacteria] as masters of manipulating electrons and ions in their environment. It’s a very, very far cry from the way we thought of them as very simplistic organisms.”



A Cure for Zika? Scientists successfully test a DNA-based Zika Vaccine

The Zika virus, widely known for its 2015 Latin and North America outbreak, is a mosquito-borne and transmitted virus that develops neurological complications and birth-defects in those infected. The Zika virus is able to be transmitted from a pregnant woman to her fetus, causing microcephaly– abnormal development of the brain. Currently, there exists no vaccine that would fully treat the virus, however, a solution may be in the works.

(Photo from Wikipedia Commons)

David B. Weiner, Ph.D., an executive vice president of The Wistar Institute and a developer of the Zika vaccine notes that, “Synthetic DNA vaccines are an ideal approach for emerging infectious diseases like Zika”. Synthetic DNA vaccines are vaccines with genetically engineered DNA. They work in the same way as regular vaccines, inciting cells to produce specific antigens for immunological responses. Synthetic DNA vaccines can also have potential benefits over traditional vaccines, including a higher predictability, stability, and ability to be manufactured and distributed safely and rapidly.

The current Zika vaccine in development, GLS-5700, houses multiple strains of genes with DNA instructions that tell a hosts’ cells how to react and fight off a Zika virus antigen. In late 2016, researchers tested the vaccine on 40 participants. Two groups of 20 received different does of the vaccine at zero, four, and twelve week intervals. At the end of the experiment, researchers found that all participants had developed Zika-specific antibodies and 80 percent of the participants developed neutralizing antibodies against the Zika virus.

Zika 2015-2016 Outbreak (Photo from Wikipedia Commons)

Although rare in the United States, Zika continues to threaten millions living in South and Central America. Despite being in its last stages of development, GLS-5700 and other Synthetic DNA vaccines are still prohibited from being used in the United States- although this may change with the introduction of the Zika vaccine. The future of Synthetic DNA vaccines and viral disease prevention lies in the success of the GLS-5700.





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