DNA is the single most important molecule found within cells. It is a stable polynucleotide, which contains coded information for inherited characteristics. It is contained in chromosomes in the nucleus of an eukaryot cell. The essential features of the Watson-Crick model are summarised below.
1. The two helical polynucleotide chains are coiled around a common axis. The two chains have opposite polarity i.e. they are antiparrallel.
2. The regular repeating sugar phosphate backbone of each strand lies on the outside of the helix. The purine and pyrimidine bases project inwards at 900 to the axis of the helix.
3. The two strands are held together by hydrogen bonding between pairs of bases such that guanine always pairs with cytosine and adenine always pairs with thymine; this is called complementary base pairing
3. The diameter of the helix is 2.0 nm and adjacent bases are separated by 0.34 nm and inclined at 360 relative to each other. This means that each complete turn of the double helix contains about 10 base pairs.
4. The amount of guanine is usually equal to that of cytosine.
The monomers of RNA and DNA are called nucleotides. Each nucleotide has three parts:
A Five Carbon or Pentose Sugar
The sugar will be one of two very similar pentose rings. Ribonucleic acids contain the sugar ribose. Deoxyribonucleic acids contain the sugar deoxyribose. The only difference between these two sugars is that deoxyribose contains one oxygen atom less than ribose. Pentose sugars are essential because they are involved in linking different nucleotides together by condensation reactions.
The Nitrogen-Containing Bases
There are two types of bases found in nucleic acids. The purine bases have two nitrogen containing rings, while the pyrimidines have only one. In DNA the purines are adenine (A) and guanine (G) and the pyrimidines are cytosine (C) and thymine (T). In RNA the purine bases are the same as in DNA, but the pyrimidines are cytosine and uracil (U). These rings have the chemical property of being bases because of the nitrogen atoms they contain.
Adenine always forms 2 hydrogen bonds with thymine.
Cytosine always forms 3 hydrogen bonds with guanine.
Miller, Kenneth R. and Joseph S. Levine. “Chapter 12: DNA and RNA.” Biology. Upper Saddle River: Pearson Education, Inc., 2002. Print.
DNA is the genetic material found in cells of all living organisms. Human beings contain approximately one trillion cells (Aronson 9). DNA is a long strand in the shape of a double helix made up of small building blocks (Riley). The repeat segments are cut out of the DNA strand by a restrictive enzyme that acts like scissors and the resulting fragments are sorted out by electrophoresis (Saferstein 391).
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The study of nucleic acids has now become a fruitful and dynamic scientific enterprise. Nucleic acids are of unique importance in biological systems. Genes are made up of deoxyribonucleic acid or DNA, and each gene is a linear segment, or polymer, of a long DNA molecule. A DNA polymer, or DNA oligonucleotide, contains a linear arrangement of subunits called nucleotides. There are four types of nucleotides. Each nucleotide has three components; a phosphate group, a sugar and a base that contains nitrogen within its structure. The sugar moiety in DNA oligonucleotides is always dexoyribose, and there are four alternative bases: adenine (A), thymine (T), guanine (G), and cytosine (C). The phosphate groups and the deoxyribose sugars form the backbone of each DNA stand. The bases are joined to the deoxyribose sugar and stick out to the side. Both oligomers, DNA and RNA, consist of 5’->3’ phosphodiester-linked nucleotide units that are composed of a 2’-deoxy-D-ribose (DNA) or D-ribose (RNA) in their furanose forms and a heteroaromatic nucleobase (A, T, G, and C; A, U, G, C), and the resulting oligonucleotide chain is composed of a polar, negatively charged sugar-phosphate backbone and an array of hydrophobic nucleobases. The amphiphilic nature of these polymers dictates the assembly and maintenance of secondary and tertiary structures the oligonucleotides can form. In the DNA duplex structure, genetic information is stored as a linear nucleotide code. This code can be accessed and replicated. RNA, or ribonucleic acid, is another structurally related essential biopolymer. RNA differs from DNA in having the sugar ribose in place of the deoxyribos...
In April of 1953, James Watson and Francis Crick published a game changing paper. It would blow the mind of the scientific community and reshape the entire landscape of science. DNA, fully knows as Deoxyribonucleic Acid is the molecule that all genes are made of. Though it is a relatively new term with regard to the age of science, the story of DNA and the path to its discovery covers a much broader timeframe and had many more contributors than James Watson and Francis Crick. After reading the paper the audience should have a better understanding of what DNA is, the most important experiments that contributed to its ultimate discovery and the names and contributions of the lesser-known scientists that helped Watson and Crick turn their idea
An example of pentoses is ribsomes and deoxyribsome. These sugars are found in the nucleic acid of DNA and RNA. Examples of hexoses are glucose and fructose. It is an important source of energy in respiration found in many sweet tasting fruits. There are four different types of hexose sugars.
Deoxyribo Nucleic Acid (DNA) is a chromosome found in the nucleus of a cell, which is a double-stranded helix (similar to a twisted ladder). DNA is made up of four bases called adenine (A), thymine (T), guanine (G), and cytosine (C), that is always based in pairs of A with T and G with C. The four bases of A, C, G, and T were discovered by Phoebus Levene in 1929, which linked it to the string of nucleotide units through phosphate-sugar-base (groups). As mention in Ananya Mandal research paper, Levene thought the chain connection with the bases is repeated in a fix order that make up the DNA molecu...
... the codon for the amino acid methionine is added the head of each chain.
strands which make up the letters of a genetic code. In certain regions of a DNA strand
DNA is a double-stranded helix, with the two strands connected by hydrogen bonds. A base are always paired with Ts, and Cs are always paired with Gs, which is consistent with and accounts for ...
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