问题 |
答案 |
Which base is found almost exclusively in RNA? 开始学习
|
|
Uracil is a nucleotide, which are the building blocks of DNA, except uracil replaces thymine in RNA. So uracil is the nucleotide that is found almost exclusively in RNA.
|
|
|
How many carbon atoms does Uracil comprise? paɪˈrɪmɪˌdiːn Some well-known pyrimidine compounds include cytosine, thymine, and uracil, present in nucleic acids; thiamine (vitamin B1); and sulfadiazine, sulfamerazine, and sulfamethazine, drugs used in therapy of bacterial and viral diseases. 开始学习
|
|
paɪˈrɪmɪˌdiːn Pyrimidine, any of a class of organic compounds of the heterocyclic series characterized by a ring structure composed of four carbon atoms and two nitrogen atoms. The simplest member of the family is pyrimidine itself, with molecular formula C4H4N2.
|
|
|
a polyhedron with 20 faces Zwanzigflächner The name comes from Ancient Greek εἴκοσι meaning "twenty" and from Ancient Greek ἕδρα meaning "seat". 开始学习
|
|
Ikosaeder [ikozaˈʔeːdɐ] «aɪˌkɒsəˈhiːdrən» In geometry, the great icosahedron is one of four Kepler–Poinsot polyhedra.
|
|
|
Which base is found exclusively in DNA? Also known as 5-methyluracil, it is a pyrimidine nucleobase, which pairs with adenine (A), a purine nucleobase. 开始学习
|
|
In thymine, the groups at C-4 and C-2 are hydrogen acceptors, and N-3 is a hydrogen donor. (Only two of these sites, C-4 and N–3, are used to form base pairs in DNA.)
|
|
|
Unlike uracil, at the 5' thymine has a 开始学习
|
|
Thymine has a methyl group at the 5’ position, distinguishing it from uracil, which has hydrogen at that position.
|
|
|
UV rays on DNA may trigger the formation of When exposed to ultraviolet radiation, covalent bonds are formed between adjacent thymine molecules on the same strand of DNA. 开始学习
|
|
In case of thymine adjacent to a cytosine, the resulting fusion is a thymine-cytosine dimer in which the thymine is linked via its carbon atom 6 to the carbon atom 4 of cytosine.
|
|
|
English doctor, the pioneer of smallpox vaccination and the father of immunology A satirical cartoon of 1802 showed people who had been vaccinated sprouting cow's heads. 开始学习
|
|
Jenner carried out research in a number of other areas of medicine and was also keen on fossil collecting and horticulture. He died on 26 January 1823.
|
|
|
What is «the motion of dispersed particles relative to a fluid under the influence of a spatially uniform electric field»? It is used in laboratories to separate macromolecules based on size. 开始学习
|
|
Isoenzymes are generally identified in the clinical laboratory by electrophoresis.
|
|
|
alternative forms of the same enzyme activity that exist in different proportions in different tissues. They are generally identified in the clinical laboratory by electrophoresis. 开始学习
|
|
Isoenzymes differ in amino acid composition and sequence and multimeric quaternary structure; mostly, but not always, they have similar (conserved) structures.
|
|
|
It is the simplest of all ketones This molecule is only transient, as the end products are carbon dioxide and water, but clever physicians may detect metabolic disorders by the distinctive, somewhat sweet smell of elevated concentrations on the breath of a patient. 开始学习
|
|
In 1916 the petrochemical industry was still in its infancy and a fairly inefficient method using calcium acetate as the staring material was used to make acetone.
|
|
|
Coordinate covalent bonds form when one atom provides Donator-Akzeptor-Bindung bilden sich, wenn ein Atom «ein freies Elektronenpaar» bereitstellt. 开始学习
|
|
a lone pair of electrons. It is not as if the two conventional bonds in the CO molecule are stronger or different in any other way than the coordinate covalent bond.
|
|
|
the Finnish 19-letter word saippuakivikauppias, is the world's longest 5’ – G A A T T C – 3’ 3’ – C T T A A G – 5’ 开始学习
|
|
Recently a research genome sequencing project discovered that many of the bases on the Y-chromosome are arranged as palindromes
|
|
|
ancient egypt: the host of god itself heilige Stier 开始学习
|
|
According to one myth, the Apis was the living embodiment of Ptah while he lived and Osiris when he died.
|
|
|
ancient egypt: protective goddess The ancient Egyptians placed great value on cats as they protected the crops and slowed the spread of disease by killing vermin. 开始学习
|
|
Bubastis was the capital of ancient Egypt for a time during the Late Period, and a number of pharaohs included the goddess in their throne names.
|
|
|
Catabolic pathways releasing energy are not thermodynamically spontaneous a chemical reaction in which the Gibbs free energy (G) of the products is greater than the Gibbs free energy of the reactants 开始学习
|
|
/ˌek.səˈɡɒn.ɪk/ An exothermic reaction is an exergonic reaction in which energy is released in the form of heat.
|
|
|
Anabolic pathways absorbing energy are thermodynamically spontaneous a chemical reaction in which the Gibbs free energy (G) of the products is smaller than the Gibbs free energy of the reactants 开始学习
|
|
/ˌen.dəˈɡɒn.ɪk/ The term anabolism refers to those endergonic metabolic pathways involved in biosynthesis, converting simple molecular building blocks into more complex molecules, and fueled by the use of cellular energy.
|
|
|
Who invented the PCR technology? 开始学习
|
|
In 1985, Kary Mullis invented the process known as polymerase chain reaction (PCR), in which a small amount of DNA can be copied in large quantities over a short period of time.
|
|
|
The conquest of Constantinople was led by Sultan His swan song victory came in 1480, when he triumphed in Otranto, Italy, and was next planning moves to draw closer to Rome. 开始学习
|
|
On May 29 1453, Constantinople finally fell, earning Mehmed II the well-deserved title of "conqueror."
|
|
|
How many times is the average size of bacteria larger than that of viruses? 开始学习
|
|
An average virus is about eight times bigger than a ribosome, whereas the average bacteria is about 30 times bigger than your average virus.
|
|
|
Along with adenine and cytosine, it is present in both DNA and RNA it provides a pearly iridescent effect. It is also used in metallic paints and simulated pearls and plastics. 开始学习
|
|
With the formula C5H5N5O, guanine is a derivative of purine, consisting of a fused pyrimidine-imidazole ring system with conjugated double bonds.
|
|
|
It binds to cytosine through three hydrogen bonds. it provides a pearly iridescent effect. It is also used in metallic paints and simulated pearls and plastics. 开始学习
|
|
In guanine, the group at C-6 is a hydrogen acceptor, and N-1 and the amino group at C-2 are hydrogen donors.
|
|
|
In Watson-Crick base pairing, it forms three hydrogen bonds with guanine. (an amine group at position 4 and a keto group at position 2) 开始学习
|
|
The amino groups of adenine and cytosine are hydrogen donors, and the ring nitrogen atoms (N-1 in adenine and N-3 in cytosine) are hydrogen acceptors. Cytosine also has a hydrogen acceptor group at C-2
|
|
|
the causative organism for tuberculosis The bacterium is also known as "Koch's bacillus". The rising number of drug-resistant TB cases warrants novel strategies urgently to eliminate Mtb. 开始学习
|
|
Mycobacterium tuberculosis First discovered in 1882 by Robert Koch, M. tuberculosis has an unusual, waxy coating on its cell surface primarily due to the presence of mycolic acid.
|
|
|
the causative agent for lockjaw a rod-shaped, Gram-positive bacterium, typically up to 0.5 μm wide and 2.5 μm long If inoculated into a wound, the spindle can grow and produce a potent toxin, tetanospasmin, which interferes with motor neurons. 开始学习
|
|
In World War I, injection of tetanus antiserum from horses was widely used as a prophylaxis against tetanus in wounded soldiers, leading to a dramatic decrease in tetanus cases over the course of the war.
|
|
|