![]() Two types of pentose are found in nucleotides, deoxyribose (found in DNA) and ribose (found in RNA). When a polynucleotide is formed, the 5â² phosphate of the incoming nucleotide attaches to the 3â² hydroxyl group at the end of the growing chain. The base is attached to the 1â² position of the ribose, and the phosphate is attached to the 5â² position. Carbon residues in the pentose are numbered 1â² through 5â² (the prime distinguishes these residues from those in the base, which are numbered without using a prime notation). A nucleotide is made up of three components: a nitrogenous base, a pentose sugar, and one or more phosphate groups. Each nitrogenous base in a nucleotide is attached to a sugar molecule, which is attached to one or more phosphate groups. Each nucleotide is made up of three components: a nitrogenous base, a pentose (five-carbon) sugar, and a phosphate group ( Figure). The nucleotides combine with each other to form a polynucleotide, DNA or RNA. Other types of RNAâlike rRNA, tRNA, and microRNAâare involved in protein synthesis and its regulation.ĭNA and RNA are made up of monomers known as nucleotides. This intermediary is the messenger RNA (mRNA). ![]() The DNA molecules never leave the nucleus but instead use an intermediary to communicate with the rest of the cell. The other type of nucleic acid, RNA, is mostly involved in protein synthesis. DNA controls all of the cellular activities by turning the genes âonâ or âoff.â Many genes contain the information to make protein products other genes code for RNA products. A chromosome may contain tens of thousands of genes. In eukaryotic cells but not in prokaryotes, DNA forms a complex with histone proteins to form chromatin, the substance of eukaryotic chromosomes. The entire genetic content of a cell is known as its genome, and the study of genomes is genomics. In prokaryotes, the DNA is not enclosed in a membranous envelope. It is found in the nucleus of eukaryotes and in the organelles, chloroplasts, and mitochondria. DNA is the genetic material found in all living organisms, ranging from single-celled bacteria to multicellular mammals. The two main types of nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
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