Genetics & Molecular Biology
The cell membrane at first may seem a simple device, but it is in fact a very complex machine. The basic building block is the phospholipid, a set of molecules that have hydrophilic (water loving) heads on one side and a hydrophobic (water hating) tail on the other. Because of this relationship the water loving heads want to be near aqueous environments and the water hating tails like to be near other water hating tails, or fats. Since cells live in aqueous environments, and are filled with aqueous fluids the cell membrane forms two layers with the heads pointing out and the tails pointing towards each other.
Proteins are the workhorses of our existence. These "helmsmen of the cell" are composed of amino acids, whose sequence is already defined by the heritable information in every living being and transport substances, convey messages and carry out vital processes in their role as molecular machines.
The translation of this information during the production of proteins (protein synthesis) is determined by the genetic code and 20 amino acids form the standard set of which proteins are built.
Retinitis pigmentosa are a diverse group of hereditary diseases that lead to incurable blindness and affect two million people worldwide. Though the causes are diverse, the manifestation of the disease is similar: highly sensitive rod photoreceptors, which allow us to see at dusk, die first and the cones that operate during daylight and are responsible for high-resolution color vision follow.
This is what your next doctor's visit will sound like after you get your genome sequenced:
Scientists from the Institute of Biochemistry and Molecular Biology and Collaborative Research Center 746 of the University of Freiburg say they have discovered a new mechanism which plays an essential role in the assembly and growth of mitochondria, the 'power plants' of the cell.
These organelles make energy stored in food ready for use by the cell. The generators in the cellular power plants are biological membranes located inside the mitochondria. Even minute errors in the composition of the inner mitochondrial membrane can lead to severe metabolic derangements, which can have an especially negative impact on the energy-hungry muscle and nerve cells.
During pregnancy, many women experience remission of autoimmune diseases like multiple sclerosis and uveitis and scientists have described a biological mechanism they say is responsible for changes in the immune system that helps explain that remission.
The expression of an enzyme known as pyruvate kinase is reduced in immune cells in pregnant women compared to non-pregnant women, says biophysicist Howard R. Petty from the University of Michigan Kellogg Eye Center, and Roberto Romero, M.D., of the National Institutes for Health. Their study coming in the August issue of the American Journal of Reproductive Immunology also reports that expression of the enzyme is lower in pregnant women compared to those with pre-eclampsia, a condition with inflammatory components.
Regarding the recent Nature News article (Transcription: Enhancer makes non-coding RNA. Nature 465, 173-174; 2010) about the discovery of enhancer RNAs (eRNAs) and their apparent link with neuronal activity, an initial question that arises is whether these eRNAs are really a new class of small RNAs. The question stems from the striking similarities between eRNAs and microRNAs.
Researchers have come a long way from initially cracking the DNA code since the time of Watson and Crick, to now unveiling the complex layers of molecular codes that make up the cell’s molecular fingerprint.
These codes are no longer restricted to the 4 nucleotide codes of the DNA sequence, but rather a complex web of coding systems that regulate every stage of gene expression, including the epigenetic codes (transcriptional), microRNA codes (translational), as well as codes derived from alternative splicing of RNA transcripts (post-translational). While the existence of these codes are now dogma to most cell biologists, precisely how these codes dictate the identity of cells in a multicellular organism still remains elusive.
Hummingbirds require an enormous amount of energy to beat their wings fast enough to hover and maneuver. In many ways they appear to retain some of the flight patters of insects, but they have an enormous amount of mass in comparison. Many changes in cell structure must occur to allow this high metabolism rate, and most specifically in mitochondria to be able to provide such large quantities of energy.
Quite a few changes in cell morphology and physiology might be expected to help deal with these large metabolism rates. Greater oxygen and carbon dioxide diffusion rates in the lungs would speed the movement of these gasses, as well as increased cardiac output and increase in capillary density.
A new study published in Genome Research has identified intrinsic properties of DNA that influence mutation rate, shedding light on an area of biology that still needs to be investigated - the mechanisms involved in genome maintenance .
Some DNA mutations are subject to natural selection, either conferring a biological advantage that is selected for, or a negative effect that is selected against. Mutations not under selection are said to be neutral, and the rate at which neutral mutations accumulate is reflective of the true DNA mutation rate. Researchers can estimate this mutation rate by comparing neutrally evolving sequences in species that share a common ancestor.