What is the difference between nucleotides and nitrogen bases

The DNA is wrapped tightly around the histone core. This nucleosome is linked to the next one by a short strand of DNA that is free of histones. This fiber is further coiled into a thicker and more compact structure. At the metaphase stage of mitosis, when the chromosomes are lined up in the center of the cell, the chromosomes are at their most compacted. They are approximately nm in width, and are found in association with scaffold proteins.

In interphase, the phase of the cell cycle between mitoses at which the chromosomes are decondensed, eukaryotic chromosomes have two distinct regions that can be distinguished by staining. There is a tightly packaged region that stains darkly, and a less dense region.

The darkly staining regions usually contain genes that are not active, and are found in the regions of the centromere and telomeres. The lightly staining regions usually contain genes that are active, with DNA packaged around nucleosomes but not further compacted. Concept in Action. Watch this animation of DNA packaging. The DNA molecule is a polymer of nucleotides. Each nucleotide is composed of a nitrogenous base, a five-carbon sugar deoxyribose , and a phosphate group. There are four nitrogenous bases in DNA, two purines adenine and guanine and two pyrimidines cytosine and thymine.

A DNA molecule is composed of two strands. Each strand is composed of nucleotides bonded together covalently between the phosphate group of one and the deoxyribose sugar of the next. From this backbone extend the bases. The bases of one strand bond to the bases of the second strand with hydrogen bonds. Adenine always bonds with thymine, and cytosine always bonds with guanine.

The bonding causes the two strands to spiral around each other in a shape called a double helix. Ribonucleic acid RNA is a second nucleic acid found in cells.

RNA is a single-stranded polymer of nucleotides. For now, when we discuss nucleic acids you should assume we are discussing DNA rather than RNA, unless otherwise specified. A nucleotide consists of three things: A nitrogenous base, which can be either adenine, guanine, cytosine, or thymine in the case of RNA, thymine is replaced by uracil.

A five-carbon sugar, called deoxyribose because it is lacking an oxygen group on one of its carbons. One or more phosphate groups.

The nitrogen bases are pyrimidine in structure and form a bond between their 1' nitrogen and the 1' -OH group of the deoxyribose. This type of bond is called a glycosidic bond. The phosphate group forms a bond with the deoxyribose sugar through an ester bond between one of its negatively charged oxygen groups and the 5' -OH of the sugar. Nucleotides join together through phosphodiester linkages between the 5' and 3' carbon atoms to form nucleic acids.

The 3' -OH of the sugar group forms a bond with one of the negatively charged oxygens of the phosphate group attached to the 5' carbon of another sugar. If one hydroxyl OH group has been removed from the ribose, the deoxy versions of the nucleoside and nucleotide form the building blocks of deoxyribonucleic acid or DNA Figure Each component of nucleosides and nucleotides is discussed below.

Basic Structure of Nucleosides and Nucleotides. Five major nucleoside bases are common in human biology, including the purines two-ring structure adenine and guanine top and the pyrimidines one-ring structure cytosine, uracil, and thymine middle. Nucleosides bottom are made of a nitrogenous base, usually either a purine or pyrimidine, and a five-carbon carbohydrate ribose. A nucleotide is simply a nucleoside with an additional phosphate group or groups blue ; polynucleotides containing the carbohydrate ribose are known as ribonucleotide or RNA.

Nitrogenous base—The nitrogenous base of a nucleoside or nucleotide named because of the nitrogen atoms found in its structure may be either a purine or a pyrimidine.

Purines , including inosine I , adenine A , and guanine G , are two-ring structures and pyrimidines , including uracil U , cytosine C , and thymine T , have only one ring Figure Both purine and pyrimidine nitrogenous bases are made, in part, from amino acids as shown in Figures and Your MyAccess profile is currently affiliated with '[InstitutionA]' and is in the process of switching affiliations to '[InstitutionB]'.

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