Wednesday, January 26, 2011


Why do some things float and others sink? The first thing that comes to mind for many people is that it depends on how heavy an object is. While an object's weight, or more properly its mass* does play a role, it is not the only factor. If it were, we could not explain how a giant ocean liner floats while a small pebble sinks. Mass matters, but there is more to it.
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Saturday, January 22, 2011

Serial Dilutions

***UPDATE- View the updated illustration at

Many modern biology and chemistry laboratory procedures require compounds to be mixed or dissolved in a liquid such as water.  These mixtures are called solutions.  Solutions have two components: a solute and a solvent.  Solutes are the suspended or dissolved material and the liquid is the solvent.  The amount of solute present in a particular volume of water or other solvent is called its concentration. For chemicals, common concentration units include weight/volume percent, weight percent, molarity and normality.  For biologically active compounds such as antibodies or enzymes, concentrations are often described using activity units/ml.  Concentration of bacterial and cell cultures are often reported in cells / ml or CFU (colony forming units)/ml.

Thursday, January 13, 2011

Alleles, genotype and phenotype

Genetics is the study of the organization, expression and transfer of heritable information. The ability for information to pass from generation to generation requires a mechanism. Living organisms use DNA. DNA is a chain, or polymer, of nucleic acids. Individual polymers of DNA can contain hundreds of millions of individual nucleic acids molecules. These long DNA strands are called chromosomes. Information is contained in the order of the individual nucleic acids that make up the DNA polymer. The use of DNA as the information molecule is a universal property of all life on Earth. Genetic information is read by our cellular machinery and allows our bodies to synthesize the many enzymes and proteins required for life

Friday, January 7, 2011

Types of waves

Every sound we hear, every photon of light that hits our eyes, the movement of grass blown by the wind and the regular beat of the tides are all examples of waves. They are all around us.  Visible, physical waves such as those we see when a rock is thrown into water are what many people think about when they first began to think about waves. These waves have distinct properties specific to their type but also exhibit characteristics in common with more abstract waves such as sound waves and light (electromagnetic) waves.