Thursday, Day 4
In 1997, a baby sheep named Dolly introduced the world to reproductive cloning. She was a clone because she and her mother shared the same nuclear DNA; in other words, their cells carried the same genetic material. They were like identical twins reared generations apart.
Scientists at the Roslin Institute in Scotland created Dolly by a process called nuclear transfer. Taking the genetic material from an adult donor cell, they transferred it into an unfertilized egg whose genetic material had been removed. In Dolly's case, the donor cell came from the mammary gland of a six-year-old Finn Dorset ewe. The researchers then gave the egg an electric shock, and it began dividing into an embryo.
One of the reasons Dolly's creation was so astounding was that it proved to the scientific community that a cell taken from a specialized part of the body could be used to create a whole new organism. Before Dolly, almost all scientists believed that once a cell became specialized it could only produce other specialized cells: A heart cell could only make heart cells, and a liver cell could only make liver cells. But Dolly was made entirely from a cell extracted from her mother's mammary gland, proving that specialized cells could be completely reprogrammed.
In many ways, Dolly was not like her mother. For example, her telomeres were too short. Telomeres are thin strands of protein that cap off the ends of chromosomes, the structures that carry genes. Although no one is sure exactly what telomeres do, they seem to help protect and repair our cells. As we age, our telomeres get shorter and shorter. Dolly received her mother's six-year-old telomeres, so from birth, Dolly's telomeres were shorter than the average lamb her age. Although Dolly appeared to be mostly normal, she was put to sleep in 2004 at the age of six, after suffering from lung cancer and crippling arthritis. The average Finn Dorset sheep lives to age eleven or twelve.
Since 1997, cattle, mice, goats, and pigs have been successfully cloned using nuclear transfer.
The success rate for cloning is very low in all species. Published studies report that about 1 percent of reconstructed embryos survive birth. But since unsuccessful attempts largely go unreported, the actual number might be much lower.
Before she died, Dolly was the mother of six lambs, all bred the old-fashioned way.
A group of Korean researchers claimed to have cloned a human embryo in 1998, but their experiment was terminated at the 4-cell stage, so there was no evidence of their success.
Friday, Day 5
Music: The Basics
Music is organized sound that can be replicated through imitation or notation. Music is distinct from noise in that the sounds of a door creaking open or fingernails on a blackboard are irregular and disorganized. The sound waves that map these noises are complex and cannot be heard as identifiable pitches.
Some of the basic ways that we analyze musical sounds are:
Pitch: How high or how low a sound is to the ear. Pitch is measured technically by the frequency of a sound wave, or how often waves repeat themselves. In western music there are twelve unique pitches (C, C-sharp or D-flat, D, D-sharp or E-flat, E, F, F-sharp or G-flat, G, G-sharp or A-flat, A, A-sharp or B-flat, and B). The pitches followed by sharps or flats are called accidentals, and they are most easily described as the black keys on the piano keyboard. They are located musically, one half step between the two pitches on either side of them. For example, D-sharp and E-flat have the same pitch. When referring to pitches in the context of notated, or written music, they are called notes.
Scale: A stepwise arrangement of pitches (for example, C, D, E, F, G, A, B, C) that often serves as the basis for a melody. A piece, or a portion of a piece, will often use only notes found in a particular scale. Western music primarily uses the major scale or the minor scale, in one form or another. To most people, the major scale, because of its particular arrangement of pitches, has the quality of sounding "bright," "happy," or "positive." A minor scale, likewise, is usually described as "dark," "sad," or "pessimistic."
Key: An arrangement or system of pitches, usually based on one of the major or minor scales, that is meant to serve as a reference point and a guiding force of a melody. The tonic of a key is often the starting and ending point for a piece written in a particular key -- so if a piece is in E major, then the pitch E will serve as the piece's tonal center.
All of these basic elements can be notated on the staff, which is a repeating of five parallel horizontal lines. Often it is divided into measures to indicate metric divisions in the piece and marked at the beginning of each staff of the page with a clef to indicate reference points for identifying pitches.
When a piece strays from its basic key, this is called modulation. Keys are indicated in written music by a key signature at the beginning of each staff.
There are hundreds of scales used in the world's many different musical cultures. In India, music played on the sitar and other instruments chooses pitches from a collection of twenty-two possibilities, with the distances between scale steps sometimes larger and sometimes smaller than those used in Western music. This can make differences between pitches extremely subtle and demands a high virtuosity from Indian classical musicians.