Related to this Question. In DNA and RNA, cytosine. How would you pronounce Thymidine?Definition Deoxyribonucleic acid (abbreviated DNA) is the molecule that carries genetic information for the development and functioning of an organism. Uracil: Definition & Structure. Sample translated sentence: 5-(e)-bromovinyl uracil analogues and related pyrimidine nucleosides as anti-viral agents and methods of use ↔ Analogues uracile 5-(e)- bromovinyl et nucleosides pyrimidines associes ayant la fonction d'agents anti-viraux et procedes. Also called: 5-methyl uracil. Name the four nitrogenous bases that are found in DNA. 4K . 00:00. Thus, it only has one ring. In RNA, thymine is replaced with uracil. Ultraviolet light may dimerize adjacent cytosine or thymine bases. U A pyrimidine base, C4H4N2O2, that is an. Propylthiouracil side effects. These abasic sites can be hydrolyzed by. There are three major types of RNA involved in this process: (1) messenger RNA (mRNA), (2) transfer RNA (tRNA), and (3) ribosomal RNA (rRNA). Background Detection of somatic mutations is a mandatory practice for therapeutic definition in precision oncology. Thus, adenine complementary base pairs with uracil in RNAs. Noun [ edit] uracilo m (plural uracilos) ( organic chemistry) uracil. Definition: Gene. Biochemistry a pyrimidine base, C 4 H 4 N 2 O 2, that is one of the fundamental components of RNA, in which it forms base pairs with adenine. It has a role as a metabolite, a human metabolite, an Escherichia coli metabolite and a mouse metabolite. It has a melting point of 316- 317 °C. Tegafur is converted to fluorouracil by the CYP isoenzymes, and uracil prevents further degradation by competitive inhibition of dihydropyrimidine dehydrogenase [2 R]. Which of the following is found in protein, but is not found in DNA? (a) Sulfur (b) Phosphorous (c) Carbon (d) Nitrogen (e) Oxygen. Learn the function of uracil, as well as its properties. Quotes. uracile, U are the top translations of "uracil" into French. The structures of polynucleotide strands of both DNA and RNA molecules can be understood in terms of sugar-phosphate backbones. Uracil is a pyrimidine base that is used in RNA in place of thymine. Uracil is a pyrimidine nucleobase with a chemical formula of C 4 H 4 N 2 O 2. Principal search tendencies and common uses of. 2. Both take part in nucleic acid synthesis and metabolism. from . Uracil, a colourless, crystalline organic compound of the pyrimidine family that occurs as a component of ribonucleic acid (RNA), a molecule involved in the transmission of hereditary characteristics. DNA and RNA base pairing is slightly different since DNA uses the bases adenine, thymine, cytosine, and guanine; RNA uses adenine, uracil, cytosine, and guanine. Discover if uracil is found in DNA. It has a chemical formula of C 4 H 4 N 2 O 2. Guanine, 1. CYTOSINE, GUANINE, URACIL Pronunciation Symbols. [2]uracil: [ u´rah-sil ] a pyrimidine base found in ribonucleic acid (RNA). before it is translated into protein. FIGURE 1. Uracil is planar and unsaturated and has the ability to absorb light. Like the UNG from E. 3. fluorouracil ( countable and uncountable, plural fluorouracils) ( pharmacology) A fluorine - substituted derivative of uracil C 4 H 3 FN 2 O 2 which inhibits DNA synthesis and is used as a chemotherapy drug in the treatment of cancer. A hydrogen atom is linked to the 5′-C of the uracil’s aromatic ring structure. In general, uracil occurs in RNA, not in DNA. Browse nearby or related words. Definition. 4K . Pick your prefered accent: Alex. Pyrimidines- Cytosine (C), Thymine (T; found only in DNA), Uracil (U; found only in RNA) Pentose sugar : There are two types of pentose sugars: Deoxyribose sugar (found only in DNA)Definition. When three continuous. The ribose sugar of RNA is a cyclical structure consisting of five. Rate the pronunciation struggling of Uracil. The guanine nucleoside is called guanosine . a. uracil - Meaning in English, what is the meaning of uracil in English dictionary, pronunciation, synonyms, usage examples and definitions of uracil in English and English. 4K . Julia. Guanine is defined as one of the four main bases in nucleic acids. The base-pairing rules are rules that apply during the pairing between one purine and one pyrimidine via tight hydrogen bonds (H-bonds). Codon (image) Uracil (image) Anticodon (definition) group of three bases on a tRNA molecule that are complementary to an mRNA codon. A nucleotide is made up of three parts: a phosphate group, a 5-carbon sugar, and a nitrogenous base. ↔ En ARN, la timina es reemplazada por uracilo (U). Learn how to say Thymidine with EmmaSaying free pronunciation tutorials. What is uracil in Malayalam? Pronunciation, translation, synonyms, examples, rhymes, definitions of uracil in Malayalam. Why is uracil used in RNA? Uracil is energetically less expensive for the production of thymine. Uracil-DNA Glycosylase, heat-labile contains the equally named enzyme found in the marine bacterium BMTU 3346. Uracil glycosylase quickly cleaves the uracil residue from the DNA producing an apyrimidinic site. Nov 14, 2023. ChemSpider ID 1141. US English. cytosine: [noun] a pyrimidine base C4H5N3O that codes genetic information in the polynucleotide chain of DNA or RNA — compare adenine, guanine, thymine, uracil. Nucleotides can be further broken down to a. Tags for the entry "uracil" What uracil means in Tamil, uracil meaning in Tamil, uracil definition, explanation, pronunciations and examples of uracil in Tamil. Uracil is a pyrimidine base that is used in RNA in place of thymine. Learn the function of uracil, as well as its properties. Heterocyclic compounds are stable, ring-shaped compounds in which not. Another marked difference is the uracil of RNA in place of thymine in DNA. In the related molecule RNA, thymine is replaced by its close relative uracil, so the pairs are adenine-uracil and guanine-cytosine. Translation of "uracil" into French . Uracil has a melting point of 335 °C. 2. Translation of "uracil" into Serbian . It has a chemical formula of C 4 H 5 N 3 O. They were first described by Dr. US English. Instead of uracil, DNA has thymine that pairs. Its nucleoside contains a pyrimidine base, i. a pyrimidine base, C 4 H 4 N 2 O 2 , that is one of the fundamental components of RNA, in which it forms base pairs with adenine. The nucleotide bases are made up of purines (adenine and. Uracil is. Uracil is a demethylated form of thymine, and replaces thymine in RNA. Thymine Definition. Symbol. See examples of. amino acids are bounded together into a polypeptide chain in a sequence specified by base triplets in messenger RNA; Transfer RNA delivers amino acids one at a time to ribosomes an RNA component of ribosomes catalyzes the chain-building reaction. - A base containing nitrogen that is found in RNA (but not in DNA) and derived from pyrimidine. It is a planar, unsaturated compound that has the ability to absorb light. Refine your pronunciation of uracil with our free online dictionary. [1] It was patented in 1967 and approved for medical use in 1972. As aforementioned, uracil is a pyrimidine component of the RNA. Translation. Understand the definition and structure of the compound uracil. See full answer below. . e. Record yourself saying 'uracil' in full sentences, then watch yourself and listen. Define uracil. Hydrogen bonds form between adenine and uracil, guanine and cytosine, and also guanine and uracil. a base containing nitrogen that is found in RNA (but not in DNA) and derived from pyrimidine; pairs with adenine. URACIL definition: a pyrimidine present in all living cells , usually in a combined form, as in RNA. thymine c. : 250 The other diazines are pyrazine (nitrogen atoms at the. Uracil (U) is one of the four nucleotide bases in RNA, with the other three being adenine (A), cytosine (C) and guanine (G). a base containing nitrogen that is found in RNA (but not in DNA) and derived from pyrimidine; pairs with adenine Synonyms : U; SHABDKOSH Apps. Select Speaker Voice. On degradation, uracil produces substrates such as carbon dioxide. Games. (FAU, NCI Dictionary) It is a combination of tegafur and uracil. Pronunciation of Tegafur Uracil with 2 audio pronunciations and more for Tegafur Uracil. A nucleic acid base (or nucleobase) is a nitrogen heterocyclic compound, which serves as the informational monomer of ribonucleic acids (RNA) and deoxyribonucleic acids (DNA), the biopolymers responsible for the storage and transmission of genetic information. RNA (ribose nucleic acid) is a complex molecule that plays a big part in living cells. This base pairing is necessary for the stability and folding of RNA molecules, and recognition of RNA sequences. The UNG gene is located on chromosome 12q24. Scientific context: - "Uracil is a pyrimidine base that replaces thymine in RNA molecules. Why is uracil used in RNA? Uracil is energetically less expensive for the production of thymine. The methylation process is the expansion of a methyl bunch(CH 3) to a molecule. Ang uracil ay hindi karaniwang matatagpuan sa DNA na umiiral lamang bilang nasirang produkto ng cytosine. The response rate is improved by adding leucovorin [ 107R ]. OneDefinition. Pronunciation of uracil. Uracil is only found in RNA, while thymine is only found in DNA. Discover if uracil is found in DNA. In RNA, the nucleotide thymine is replaced with _____. Norton and Company, Inc. Uracil has a molar mass of 112. 0) and 20 mM ammonium sulfate. A review of polyols – biotechnological production, food applications, regulation, labeling and health effects. Mark. Thymine is also known as 5-methyluracil, a pyrimidine nucleobase. guanine. A. 2: DNA Replication. Formula: C 4 H 4 N 2 O 2 Collins English Dictionary. A nucleotide is the basic building block of nucleic acids (RNA and DNA). How to say Thymine in English? Pronunciation of Thymine with 3 audio pronunciations, 2 synonyms, 12 translations and more for Thymine. Also called: 5-methyl uracil. Study with Quizlet and memorize flashcards containing terms like Match each vocabulary word with the letter corresponding to its correct definition. Copyright ©. You. looted b. see more. Within a double-stranded DNA molecule, thymine bases on one strand pair with adenine bases on the opposite strand. A uracil-based nucleotide is called uridine. Start Free Trial. A nucleotide is an organic molecule that is the building block of DNA and RNA. Chapter 11 / Lesson 9. Adenine and guanine are fused five - and six-membered purines, while cytosine and thymine are six-membered rings called uracil (U), replaces thymine in RNA. A pyrimidine is an organic compound known as an aromatic heterocyclic compound and has the molecular formula of C 4 H 4 N 2. The deoxyribonucleic acid (DNA) of a typical mammalian cell contains about 3 × 10 9 nucleotides. Subscribe for more videos!Here are 4 tips that should help you perfect your pronunciation of 'uracil': Break 'uracil' down into sounds : [YOOR] + [UH] + [SIL] - say it out loud and exaggerate the sounds. deviation, Use the word bank to answer the question. The consideration that cells must possess an ability to remove uracil from DNA, which arises either by misincorporation of deoxyuridine monophosphate (dUMP) during DNA replication or by hydrolytic deamination of cytosine, led to the discovery of an enzyme capable of. Powered by MaryTTS. However, there are three main differences between DNA and RNA: RNA uses the sugar ribose instead of deoxyribose. Have we pronounced this wrong? Teach everybody how you say it using the comments below!!Looking for help to learn English? Claim top deals on the best Englis. n. The chains of nucleotides in a nucleic acid are linked by 3′, 5′ phosphodiester linkages. Uracil is one of the nucleobases in the RNA, such as adenine, Guanine and cytosine where as in all living beings that contains DNA, lack uracil in its nucleotide base pairs. There are two types of nucleic acids in biology: DNA and RNA. Properties [edit | edit source]. from . The bases combine with the sugar to make the nucleotides adenosine, guanosine, cytidine, thymidine, and uridine. . It has a pyrimidine ring structure. RNA though carries the genetic information of just one gene. Properties of Uracil. 0:00 / 0:58 How to Pronounce "Uracil" 517 views May 13, 2019 0 Dislike Share Save Pronounce TV Have we pronounced this wrong? Teach everybody how you say it using. Nucleic acids. Chapter 11 / Lesson 9. Definition: A nucleic acid that contains the genetic instructions used in the development and functioning of all modern living organisms. Study with Quizlet and memorize flashcards containing terms like Definition of virulent, Definition of transformation, Definintion of bacteriophage and more. ; Methylation is completed by DNA methyltransferase. Average mass 112. Study with Quizlet and memorize flashcards containing terms like 1. The others are adenine (A), cytosine (C), and guanine (G). Definition. Translation. have an additional oxygen atom, and the base thymine. Video shows what uracil means. Translate. Discover if uracil is found in DNA. Learn the function of uracil, as well as its properties. See examples of HELICASE used in a sentence. How to properly pronounce uracil? uracil Pronunciation ˈyʊər ə sɪl uracil Here are all the possible pronunciations of the word uracil. It is possible the name you are searching has less than five occurrences per year. Related to this Question. DNA is less reactive because of C-H bonds and RNA is more reactive beacause of C-OH bonds. The two main types of nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). uracil: ChEBI ID CHEBI:17568: Definition A common and naturally occurring pyrimidine nucleobase in which the pyrimidine ring is substituted with two oxo groups at positions 2 and 4. The ribose sugar of RNA is a cyclical structure consisting of five carbons and one oxygen. Chapter 11 / Lesson 9. RNA polymerase (RNApol) is a multi-unit enzyme that is responsible for creating a complimentary strand of nucleic acid, called RNA, from a single stranded DNA template through the incorporation of adenosine, cytosine, guanine and uracil nucleotides. URACIL definition: a pyrimidine present in all living cells , usually in a combined form, as in RNA. It has a pyrimidine ring structure. Chapter 11 / Lesson 9. Functionality – Uracil is important in the formation and function of RNA, where it creates complementary base pairs with adenine. Its nucleoside contains a pyrimidine base, i. Thymine Definition. Because the phosphate groups on a ribonucleic acid molecule carry negative charges, RNA is also electrically charged. Thymine is an organic aromatic. Definition and meaning were removed to avoid copyright violation, but you can find them h. Purines. How to say uracils in English? Pronunciation of uracils with 1 audio pronunciation, 1 meaning, 2 translations and more for uracils. a base containing nitrogen that is found in RNA (but not in DNA) and derived from pyrimidine; pairs with adenine. The other nucleotide that can bond with adenine is thymine. Unlike the determination of uracil and DHU levels and the derived DHU:U ratio, which have been described in previous work, the determination of thymine and DHT levels and the derived DHT:T ratio is a relatively unexplored parameter. US English. Originally discovered in 1900, it was isolated by hydrolysis of yeast nuclein that was found in bovine thymus and spleen, herring sperm, and wheat germ. Discover if uracil is found in DNA. Origin and meaning of name Adenine. It is referred to as a pyrimidine, along with cytosine and thymine. RNA is produced as needed in response to the dynamic cellular environment and the. Here are 4 tips that should help you perfect your pronunciation of 'uracil': Break 'uracil' down into sounds : [YOOR] + [UH] + [SIL] - say it out loud and exaggerate the sounds until you can consistently produce them. Etymology: The term “thymine” is derived from the Greek word “thumos,” meaning “spirit” or “soul,” due to its association with thymus glands. Learn the function of uracil, as well as its properties. Chapter 11 / Lesson 9. 1. Thymine: Structure & Definition Quiz; Uracil: Definition & Structure Quiz; What is Deoxyribonucleic Acid? - Definition & Structure Quiz; Go to Nucleic Acids - DNA and RNA: Tutoring SolutionAdenine (not adenosine) 2. Activity is measured by release of [ 3 H]-uracil in a 50 µl reaction containing 0. B. The genetic code is the sequence of nucleotide bases in nucleic acids ( DNA and RNA) that code for amino acid chains in proteins. US English. It pairs with adenine and is symbolised by U. uracil. Each nucleotide that makes up a nucleic acid is comprised of phosphoric acid, sugar (5-carbon), and nucleobase. Guanine ( / ˈɡwɑːnɪn / ⓘ) ( symbol G or Gua) is one of the four main nucleobases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine ( uracil in RNA). a single-stranded nucleic acid that encodes genetic information. As a result, cytosine is available across both DNA and RNA, together with adenine and guanine, in DNA while only thymine is present whereas uracil is generally present instead of thymine in RNA. Structure. General Structure of Pyrimidine Class. Chapter 11 / Lesson 9. Genomic patterns of uracil enrichment upon the effect of two TS inhibitory drugs indicated a strong correlation with replication timing and, to a lesser extent, with the more actively transcribed euchromatin. DNA consists of the four nucleotide bases: adenine (A), guanine (G), cytosine (C) and thymine (T). In DNA, adenine pairs with thymine. The nucleotide sequence of RNA, which is complementary to the DNA sequence, allows RNA to encode genetic information. Francis Crick and Dr. Uracil ka hindi mein matalab, arth aur prayog. | Meaning, pronunciation, translations and examples in American English Uracil definition: A colorless, crystalline, pyrimidine base, C 4 H 4 N 2 O 2 , that occurs as a constituent of RNA. 21 views 22 hours ago. altruistic, Use the word bank to answer the question. A pyrimidine is an organic ring consisting of six atoms: 4 carbon atoms and 2 nitrogen atoms. RNA is generally single-stranded instead of double-stranded. A purine, on the other hand, has two rings of. Molecular Formula CHNO. U. A tablet formulation containing 5-ethynyluracil (GW776), an ethynyl derivative of uracil and the antineoplastic agent 5-Fluorouracil (5-FU) in a 10:1 ratio. The five nucleosides are commonly. The upp knockout mutants are unable to grow photoautotrophically, and knockdown mutants exhibit a variegated phenotype, with leaves that have chlorotic pale. Uracil . Molecular Formula. 3. Become a Study. Each strand has a backbone made of alternating sugar. a base containing nitrogen that is found in RNA (but not in DNA) and derived from pyrimidine; pairs with adenine. Each nucleotide subunit is composed of a pentose sugar (deoxyribose), a nitrogenous base, and a phosphate group. Its nucleoside contains a pyrimidine base, i. The others are adenine (A), cytosine (C), and guanine (G). Vocabulary. The meaning of URACIL is a pyrimidine base C4H4N2O2 that is one of the four bases coding genetic information in the polynucleotide chain of RNA. , USA pronunciation n. It pairs with adenine and is symbolised by U. A duplicated chromosome contains _____. One of the three diazines (six-membered heterocyclics with two nitrogen atoms in the ring), it has nitrogen atoms at positions 1 and 3 in the ring. Discover if uracil is found in DNA. Thus, it only has one ring. With the help of enzyme uracil glycosylase such defects in DNA can be. 2023-11-04. In a nucleic acid chain, a subunit that consists of a sugar, a phosphate, and a nitrogenous base. uracil noun. The sequence of the four nucleotide bases encodes DNA’s information. Uridine is a nucleoside, whereas uracil is a standalone nucleobase. Here are 4 tips that should help you perfect your pronunciation of 'uracil': Break 'uracil' down into sounds : [YOOR] + [UH] + [SIL] - say it out loud and exaggerate the sounds until you can consistently produce them. The RNA code contains a U instead of a T – uracil instead of thymine. As a nitrogenous base, cytosine is full of nitrogen atoms (it has three). This means that it has a ribose as its sugar constituent with three phosphate groups attached. The replication of DNA occurs during the synthesis phase, or S phase, of the cell cycle, before the cell enters mitosis or meiosis. Related Products. Understand the definition and structure of the compound uracil. It under normal conditions is not seen in DNA but is present in RNA replacing thymine. Subscribe for more videos!Figure 10. Understand the definition and structure of the compound uracil. Victoria. Definition and meaning can be found here:How to pronounce oropharynx and what is oropharynx. A pyrimidine is an organic compound known as an aromatic heterocyclic compound and has the molecular formula of C 4 H 4 N 2. Chapter 11 / Lesson 9. Definitions of uracil. Having been provided to the early Earth as a component in such asteroidal materials, these molecules might have played a role. These two processes are essential for life. A Dictionary of Nursing. Cytosine ( / ˈsaɪtəˌsiːn, - ˌziːn, - ˌsɪn / [2] [3]) ( symbol C or Cyt) is one of the four nucleobases found in DNA and RNA, along with adenine, guanine, and thymine ( uracil in RNA). RNA contains the nucleotides adenine, guanine, cytosine and uracil (U). A nitrogenous base that is found in RNA, replacing the thymine of DNA. 2020 Dec 12;12(12):2969. uracil - Meaning in English, what is the meaning of uracil in English dictionary, pronunciation, synonyms, usage examples and definitions of uracil in English and English. It is found in the nucleus of eukaryotes and in the organelles, chloroplasts, and mitochondria. Nucleotide Definition. Vous pouvez néanmoins effectuer une recherche ou consulter nos meilleurs articles de la semaine. Guanine (G) is one of the four nucleotide bases in DNA, with the other three being adenine (A), cytosine (C) and thymine (T). Uracil like other pyrimidines is an aromatic heterocyclic compound with a pyrimidine ring that comprises alternating nitrogen and carbon atoms. uracil noun. This can account for its utilization in RNA. U A pyrimidine base, C4H4N2O2, that is an essential constituent of RNA. In DNA, guanine is paired with cytosine. The correct answer is False. Tags for the word Uracil: Hindi meaning of Uracil, What Uracil means in hindi, Uracil meaning in hindi, hindi mein Uracil. * UK and possibly other pronunciations UK and possibly other pronunciations. In RNA it is abbreviated with a U. Biochemistry a pyrimidine base, C 4 H 4 N 2 O 2 , that is one of the fundamental components of RNA, in which it forms base pairs with. It has a deoxyribose and phosphate backbone having four distinct bases: thymine, adenine, cytosine and guanine. However, 5-bromouracil frequently pairs with thymine. A cytosine is deaminated into uracil. Contaminating Activity Assays: UNG is free of detectable exo- and endonuclease, and RNase activities. Pyrimidine bases are weakly basic. Nucleic acids, macromolecules made out of units called nucleotides, come in two naturally occurring varieties: deoxyribonucleic acid ( DNA) and ribonucleic acid ( RNA ). Definition. Uracil biosynthetic process Definition: The chemical reactions and pathways resulting in the formation of uracil, 2,4-dioxopyrimidine, one of the pyrimidine bases occurring in RNA, but not in DNA. You'll be able to mark your mistakes quite easily. Chapter 11 / Lesson 9. DNA and RNA. Uracil is similar to thymine in terms of structure except for the methyl group at position 5 in the heterocyclic aromatic ring present in thymine. Understand the definition and structure of the compound uracil. . updated: November 18, 2023 Definition 00:00 00:29 Uracil (U) is one of the four nucleotide bases in RNA, with the other three being adenine (A), cytosine (C) and guanine (G). The basic property derives from the lone electron pair on the nitrogen atom. The region of opened-up DNA is called a transcription bubble. Thymine is one of the five bases used to build nucleic acids. Pyrimidine is a heterocyclic aromatic organic compound with a single ring (called a pyrimidine ring) with alternating carbon and nitrogen atoms. Related to this Question. Hence, compared to DNA, RNA molecules are relatively small. Uracil is among the five nucleobases: adenine, guanine, cytosine, and thymine,but is only found in RNA. Transcription has three stages: initiation, elongation, and termination. The nitrogenous base (guanine in this example) is linked to the 1′ carbon of the deoxyribose and the phosphate groups are linked to the 5′ carbon. 4K . The analog is one of the five standard nucleosides which make up nucleic acids, the others being adenosine, thymidine, cytidine and guanosine. Definition of a nucleotide. It is found in the nucleus of eukaryotes and in the organelles, chloroplasts, and mitochondria. ID: GO:0046107 Synonyms: Articles referencing this term. For instance, uracil auxotroph, which is a yeast mutant, has inactivated its uracil synthesis pathway. Cytosine base bonds with guanine via 3 hydrogen bonds in nuclei acids. Base pairs refer to the sets of hydrogen-linked nucleobases that make up nucleic acids DNA and RNA. The map shown above gives the frequency of use of the term «uracil» in the different countries. DeoxyUridine (dU) can be substituted for dT in DNA oligonucleotides. Forum discussions with the word(s) "uracil" in the title:Of note, in DNA, the “Uracil” base is a slightly different base called “Thymine. . It should have Uracil replacing the Thymine as the base bonding with adenine in RNA. Adenine. 1: (a) Ribonucleotides contain the pentose sugar ribose instead of the deoxyribose found in deoxyribonucleotides. (GW776/5-Fluorouracil Combination Tablet, NCI Thesaurus) It is a type of uracil analog. Its nucleoside contains a pyrimidine base, i. Uracil and thymine have very similar structures; uracil is an unmethylated form of thymine. colorless. Video shows what uracil means. The two main types of nucleic acids are deoxyribonucleic acid (DNA)ribonucleic acid (RNA). 4 /5. • One Lindahl unit is defined as the amount of enzyme necessary to release 1 µmol uracil at +37°C in 1 minute. noun. It is generally accepted that negative discrimination against uracil in DNA is caused by the chemical instability of cytosine. A rock sample that a Japanese space probe collected from an asteroid suggests a possible source of compounds that enabled the development of life on Earth.