Muskrats are rodents that live in freshwater and saltwater marshes, lakes, ponds, and streams. Muskrats often build dome-shaped houses in marshes. These houses, made of plants, protect the muskrat from predators, since the only entrance is underwater. Some muskrats live in burrows on the water banks. Muskrats are excellent swimmers but are slow on land.
Muskrats are native to North America, but have been brought to Europe and Asia, where they now live in the wild. Muskrats got their name because they have musk glands that produce a strong scent.
Griffith's experiment
Griffith's Experiment was an experiment done in 1928 by Frederick Griffith. It was one of the first experiments showing that bacteria can get DNA through a process called transformation.
Griffith used two strains of "Streptococcus pneumoniae". He then uses the bacteria to infect the mice, which have many similar characteristics to humans. He used a type III-S (smooth) and type II-R (rough) strain. The III-S strain covers itself with a polysaccharide capsule that protects it from the host's immune system. This means that the host will die. The II-R strain does not have that protective shield around it and is killed by the host's immune system.
In this experiment, bacteria from the III-S strain were killed by heat, and their remains were added to II-R strain bacteria. While neither harmed the mice on their own, the blend of the two was able to kill mice.
Griffith was also able to get both live II-R and live III-S strains of "S. pneumoniae" from the blood of these dead mice. He concluded that the type II-R had been "transformed" into the lethal III-S strain by a "transforming principle" that was somehow part of the dead III-S strain bacteria.
Today, we know that the "transforming principle" Griffith saw was the DNA of the III-S strain bacteria. While the bacteria had been killed, the DNA had survived the heating process and was taken up by the II-R strain bacteria. The III-S strain DNA contains the genes that form the shielding polysaccharide part from attack. Armed with this gene, the former II-R strain bacteria were now protected from the host's immune system and could kill the host.
The exact nature of the transforming principle was confirmed in the experiments done by Avery, McLeod and McCarty, as well as Hershey and Chase.
Frederick Griffith
Frederick Griffith (1879 - 1941) was a English medical officer and geneticist. In 1928, during an experiment, he discovered what he called a "transforming principle", but today we call DNA.
He was born in Hale, Lancashire and attended Liverpool University where he studied genetics. In his younger days he worked at the Liverpool Royal Infirmary, the Thompson Yates Laboratory, and the Royal Commission on Tuberculosis.
The experiment began when Griffith was trying to make a vaccine to prevent pneumonia infections in the "Spanish flu" influenza pandemic after World War I, by using two strains of the "Streptococcus pneumoniae" bacterium.
Griffith was killed at work in his laboratory in 1941, along with longtime friend and bacteriologist William M. Scott in London during an air raid in the London blitz. Years later Griffith's "transforming principle" was identified as DNA by Oswald Avery, along with coworkers Colin MacLeod and Maclyn McCarty, in 1944. The Avery–MacLeod–McCarty experiment.
Streptococcus pneumoniae
Streptococcus pneumoniae, or pneumococcus, is a gram-positive, alpha-hemolytic diplococcus aerotolerant anaerobe and a member of the genus "Streptococcus". An important human pathogen, "S. pneumoniae" was recognized as a major cause of pneumonia in the late 19th century and is the subject of many humoral immunity studies.
Strain (biology)
In biology, a strain is a low-level taxonomic rank below the rank of species. This is seen in microbiology where strains are got from a single cell colony, and are quarantined by being in a Petri dish. Strains are also commonly referred to in virology, in horticulture, and with rodents used in experimental studies.
A strain is a genetic variant or subtype of a microorganism, that is to say a virus or bacterium or fungus. For example, a "flu strain" is a certain biological form of the influenza or "flu" virus. Properly speaking, bacteria, archaea and viruses do not have species, because they do not have eukaryote-type sexual reproduction. Bacteria do exchange DNA, but they may exchange it between different kinds of bacteria, which shows their difference from eukaryotes. Strains are therefore an essential part of bacterial identification.
In botany, the term is not used to rank plants. It is sometimes used to refer to all the descendants produced from a common ancestor that share a uniform morphological or physiological character. A strain is a designated group of offspring that have descended from a modified plant, produced ether by conventional breeding or by biotechnological means or result from genetic mutation.
For example, some rice strains are made by inserting new genetic material into a rice plant, all the descendants of the genetically modified rice plant are a strain with a unique genetic code that is passed on to later generations. The strain designation, a number or a formal name, covers all the plants that descend from the originally modified plant. The rice plants in the strain can be breed to other rice strains or cultivars, and if desirable plants are produced, these are further breed to stabilize the desirable traits; the stabilized plants that can be propagated and come true, are given a cultivar name and released into production to be used by farmers.
A mouse or a rat strain is a group of animals that is genetically uniform. Strains are used in laboratory experiments. Mouse strains can be inbred or genetically engineered, while rat strains are usually produced by inbreeding.
Hannes Schäfer
Dr. Johannes Schäfer, born 2nd October 1965 in Göttingen, Germany, was the bass player of the German rock band Fury in the Slaughterhouse from the beginning (1987) until 1996. Today (2008) he is a doctor.
Schäfer's first band was 1982 the punk band "Defekt" in Hanover, Germany, where he was singer and bass player. From 1985 until 1987 he played in the jazz rock band "CIT.", together with Mousse T. and at the same time he worked as a studio musician at the "Stakkato Studio" in Hannover.
In 1987 Schäfer founded the rock band Fury in the Slaughterhouse together with Kai and Christian Wingenfelder, Rainer Schumann and Christoph Stein-Schneider. He played the bass in this band until 1996, when he was followed by Christian Decker. Together with his band Schäfer was awarded golden recording sales certifications for the Fury albums "Fury in the Slaughterhouse" (1988), "Mono" (1992), and "the Hearing and the Sense of Balance" (1995). Fury in the Slaughterhouse sold about three million recordings of albums made in their time with Hannes Schäfer (1987-1996).
After leaving Fury in the Slaughterouse Schäfer studied medicine and today (2008) he works as a doctor in the hospital "Vinzenzkrankenhaus" in Hanover.
The Prestige
The Prestige is a 2006 period movie directed by Christopher Nolan. The story follows Robert Angier and Alfred Borden, enemy stage magicians in fin de siècle London. Obsessed with creating the best stage Magic, they take part in a competition with tragic results.
Javon Ringer
Javon Ringer (born February 2, 1987, Dayton, Ohio) is an American football running back for the Tennessee Titans of the National Football League (NFL). He played college football at Michigan State University. He attended Chaminade Julienne High School, where he set many running records.
Running back
A running back (RB) is the position of a player on an American football team. They are the players who carry the ball the most. They receive handoffs, catch passes, and block for other runners.
Heisman Trophy