What makes nucleotides different

Figure 4: Double-stranded DNA consists of two polynucleotide chains whose nitrogenous bases are connected by hydrogen bonds. Within this arrangement, each strand mirrors the other as a result of the anti-parallel orientation of the sugar-phosphate backbones, as well as the complementary nature of the A-T and C-G base pairing.

Figure Detail. Figure 6: The double helix looks like a twisted ladder. How is DNA packaged inside cells? Figure 7: To better fit within the cell, long pieces of double-stranded DNA are tightly packed into structures called chromosomes. What does real chromatin look like? Compare the relative sizes of the double helix, histones, and chromosomes. Figure 8: In eukaryotic chromatin, double-stranded DNA gray is wrapped around histone proteins red. Figure 9: Supercoiled eukaryotic DNA. How do scientists visualize DNA?

Figure This karyotype depicts all 23 pairs of chromosomes in a human cell, including the sex-determining X and Y chromosomes that together make up the twenty-third set lower right. Watch this video for a closer look at the relationship between chromosomes and the DNA double helix.

What are karyotypes used for? Who is James Watson? What do we know about Francis Crick? Topic rooms within Genetics Close. No topic rooms are there. Browse Visually. Other Topic Rooms Genetics. Student Voices. Creature Cast. Simply Science. Green Screen. Green Science. Bio 2. The Success Code. Why Science Matters. The Beyond. Plant ChemCast. Postcards from the Universe. Brain Metrics. Mind Read. Eyes on Environment. There are several different forms of RNA, each playing a slightly different role in the cell.

They deliver their "messages" to the protein synthesizing machinery in the cytoplasm of the cell. There are several kinds of rRNA, some are found in the large ribosomal subunit and some in the small subunit. There are more than 20 types of tRNA.

They act as the link between the genetic code and the process of joining amino acids together to form polypeptides. Deoxyribose is the pentose sugar found in this type of polynucleotide, hence its name D eoxyribo n ucleic A cid, or DNA. The nitrogenous bases found in DNA are, adenine, guanine, cytosine and thymine. DNA molecules have two polynucleotide chains, held together in a ladderlike structure. The sugar phosphate backbones of the two chains run parallel to each other in opposite directions.

DNA and RNA are nucleic acids that carry out cellular processes, especially the regulation and expression of genes. DNA is the genetic material found in all living organisms, ranging from single-celled bacteria to multicellular mammals.

It is found in the nucleus of eukaryotes and in the chloroplasts and mitochondria. In prokaryotes, the DNA is not enclosed in a membranous envelope, but rather free-floating within the cytoplasm. The entire genetic content of a cell is known as its genome and the study of genomes is genomics. In eukaryotic cells, but not in prokaryotes, DNA forms a complex with histone proteins to form chromatin, the substance of eukaryotic chromosomes.

A chromosome may contain tens of thousands of genes. Many genes contain the information to make protein products; other genes code for RNA products. The other type of nucleic acid, RNA, is mostly involved in protein synthesis. In eukaryotes, the DNA molecules never leave the nucleus but instead use an intermediary to communicate with the rest of the cell. Each nucleotide is made up of three components:. Each nitrogenous base in a nucleotide is attached to a sugar molecule, which is attached to one or more phosphate groups.

DNA and RNA : A nucleotide is made up of three components: a nitrogenous base, a pentose sugar, and one or more phosphate groups. Bases can be divided into two categories: purines and pyrimidines. Purines have a double ring structure, and pyrimidines have a single ring.

The nitrogenous bases are organic molecules and are so named because they contain carbon and nitrogen. They are bases because they contain an amino group that has the potential of binding an extra hydrogen, and thus, decreasing the hydrogen ion concentration in its environment, making it more basic. Adenine and guanine are classified as purines. The primary structure of a purine consists of two carbon-nitrogen rings. Cytosine, thymine, and uracil are classified as pyrimidines which have a single carbon-nitrogen ring as their primary structure.

Each of these basic carbon-nitrogen rings has different functional groups attached to it. In molecular biology shorthand, the nitrogenous bases are simply known by their symbols A, T, G, C, and U. The difference between the sugars is the presence of the hydroxyl group on the second carbon of the ribose and hydrogen on the second carbon of the deoxyribose.

The phosphodiester linkage is not formed by simple dehydration reaction like the other linkages connecting monomers in macromolecules: its formation involves the removal of two phosphate groups. A polynucleotide may have thousands of such phosphodiester linkages. The DNA double helix looks like a twisted staircase, with the sugar and phosphate backbone surrounding complementary nitrogen bases.

DNA has a double-helix structure, with sugar and phosphate on the outside of the helix, forming the sugar-phosphate backbone of the DNA. The nitrogenous bases are stacked in the interior in pairs, like the steps of a staircase; the pairs are bound to each other by hydrogen bonds. The two strands of the helix run in opposite directions. This antiparallel orientation is important to DNA replication and in many nucleic acid interactions. The phosphate backbone indicated by the curvy lines is on the outside, and the bases are on the inside.

Each base from one strand interacts via hydrogen bonding with a base from the opposing strand.