In molecular biology, two nucleotides on opposite complementary DNA strands that are connected by hydrogen bonds are called a base pair (often abbreviated bp).
In DNA pairing, adenine (A) forms a base pair with thymine (T),
to form an A/T base pair.
Guanine (G) pairs with cytosine (C) in DNA, to form a G/C base pair.
Complementarity (molecular biology)
In molecular biology, complementarity is a property (something that it can do) of nucleic acids such as DNA and RNA. Each nucleotide has a nitrogenous base, and each nitrogenous base can pair up with the nitrogenous base from another different nucleotide. One can say that the nitrogenous base is complementary to the other in that the base pairs between them are non-covalently bonded by hydrogen bonds.
Since there is only one complementary base for any of the bases found in DNA and in RNA, enzymes can make a complementary strand from any single strand. This is needed for DNA replication.
The bases which are complementary are
For example, the complementary strand of the DNA sequence
is
Glissando
In music a glissando is a slide up or down the notes of a scale. The plural is “glissandi”. In written music the instruction to the player is often shortened to “gliss”. The word comes from the French “glisser” = “to slide”.
With the singing voice, or with an instrument such as the trombone or a string instrument a glissando is a smooth slide in which the pitch gradually changes, becoming higher and higher. The trombonist can make a glissando by blowing whilst pushing out or pulling in the slide. The violinist can make a glissando by sliding a finger up or down the fingerboard.
With instruments such as the piano, xylophone or harp a glissando is a quick slide in which we hear one note after another because the pitches between the notes cannot be played. On the piano there are two ways to play a glissando: either on the white notes or on the black notes. At the end of the piano piece called "Ondine" from "Gaspard de la Nuit" by Maurice Ravel both these types of glissando can be heard. The pianist has to play a glissando with tips of the fingers or the finger nails. It can be quite painful to practise them a lot. Harpists are very fond of playing glissandi. By changing the position of the harp pedals a harpist can change the scale which will sound when the glissando is played.
Many modern timpani have pedals which tighten or slacken the drum head. These can be used to make a glissando. The Hungarian composer Béla Bartók often used this effect.
Some jazz clarinettists manage to play a glissando on the clarinet. They do this by gradually changing the way they blow whilst at the same time gradually lifting all the fingers off the keys. George Gershwin's "Rhapsody in Blue" starts with a glissando on the solo clarinet.
When composers write a glissando they write the first and the last note, and then put a long, straight line between the notes, and write the word “glissando” or “gliss”.
Almudena Cathedral
The Almudena Cathedral (Spanish: Catedral de la Almudena) is a Catholic cathedral in Madrid, Spain. It is one of the newest landmarks in Madrid. It is on a hilltop, next to the Royal Palace.
It was designed as long ago as 1879, but then the plans were changed to make it look like a 13th-century cathedral like the one in Rheims. Building started in 1882, but during the Spanish Civil War no more work was done do it, and the building was not finished until the 1980s. The architects who finished it, Fernando Chueca Goitia and Carlos Sidro, made some of the building look neo classical style. It was consecrated in 1993 by Pope John Paul II.
From the front of the cathedral, visitors can see parts of the old city wall which was built in the 9th century.
In May 2004 Prince Felipe, the heir to the throne, married Doña Letitia Ortiz Rocasolano in the cathedral. She was a newsreader on Spanish television.
KIO Towers
The Puerta de Europa towers (Gate of Europe or Europe's Gate or just Torres KIO) are two office buildings in Madrid. They were built in 1996 by the Kuwait Investments Office (KIO) now owned by Caja Madrid and Realia Business. Each building is 115m tall and leans 15º. They are located near Plaza de Castilla.
Portamento
In music, portamento is a gradual slide from one note to another. It is very similar to a glissando, but a glissando is deliberately written in the music by the composer and may be a long slide between two or three octaves or more. A portamento is a much shorter slide, usually between two notes which are quite close. Opera singers often used to slide from one note of a tune to another instead of singing each note separately and clearly. The habit of putting in portamento between notes spread to other instruments as well. When listening to recordings of violin playing from the early 20th century we can hear that the players used a lot of portamento.
Over the last half century portamento has gone out of fashion and singers and instrumentalists are taught not to slide from one note to another. However, there are some places, especially in opera, where it can be effective so long as it is not done all the time. It is a matter of taste.
Hydrogen bond
A hydrogen bond is a type of chemical bond that weakly attaches a molecule to another molecule. It is based on the attraction between opposite electric charges. The negative charge on an electronegative atom of one molecule is attracted to a positive charge on a hydrogen atom of another molecule. The hydrogen atom carries a positive charge because it is bonded to an second electronegative atom, which shifts electrons away from the hydrogen. This type of bond always involves a hydrogen atom, and two electronegative atoms. The electronegative atoms are often oxygen or nitrogen. Hydrogen bonds are important in polar solvents such as water and alcohol, in biomolecules, and in many other materials.
Hydrogen bonds can occur between molecules ("intermolecular" bonds), or between different parts of a single molecule ("intramolecular" bonds). The typical hydrogen bond is stronger than van der Waals forces, but weaker than covalent, ionic and metallic bonds.
Intermolecular hydrogen bonding is responsible for the high boiling point of water (100 °C). Most molecules with hydrogen bonding have high boiling points and melting points. Because hydrogen bonds are what make water stick together so well, they also help other molecules that can make hydrogen bonds dissolve in water. This is because the molecules form bonds with the hydrogen in the water, too, helping them dissolve.
Hydrogen bonds are important in many living organisms. They allow bonds between biomolecules that can be created and broken with control to allow life to proceed. For example, DNA that codes our genes contains two strands that are connected by many hydrogen bonds, like a zipper closing. Because the hydrogen bonds are not very strong, the two strands can later be "unzipped" and separated in order to read or copy the DNA. In protein molecules, intramolecular hydrogen bonds hold the protein molecule together in the shape that is needed. Intermolecular hydrogen bonds help connect protein molecules to each other to make many structures important for life, such as ribosomes that create new proteins.
Thalidomide
Thalidomide is a drug. It was used as a sedative. It also had uses for other illnesses.
It was mainly prescribed to pregnant women in the 1950s and 1960s, to help with sleep, until it was found to be a teratogen (that is: birth deformity causing substance). The drug can cause birth defects in rats, primates and humans. Before the drug was released, not enough tests were done.