Learning Objectives

By the finish of this section, girlfriend will have the ability to do the following:

Describe main point acids’ structure and define the two types of nucleic acidsExplain DNA’s structure and also roleExplain RNA’s structure and also roles

Nucleic acids room the most necessary macromolecules because that the continuous of life. They carry the cell’s genetic blueprint and carry instructions because that its functioning.

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The two main types of main point acids are deoxyribonucleic mountain (DNA) and also ribonucleic mountain (RNA). DNA is the genetic material in every living organisms, ranging from single-celled bacteria to multicell mammals. The is in the nucleus of eukaryotes and in the organelles, chloroplasts, and also mitochondria. In prokaryotes, the DNA is no enclosed in a membranous envelope.

The cell’s entire genetic content is the genome, and also the examine of genomes is genomics. In eukaryotic cells but not in prokaryotes, DNA forms a facility with histone protein to form chromatin, the substance of eukaryotic chromosomes. A chromosome may contain tens of countless genes. Many genes save the details to do protein products. Various other genes password for RNA products. DNA controls all of the cellular activities by turning the gene “on” or “off.”

The other kind of nucleic acid, RNA, is mostly associated in protein synthesis. The DNA molecules never leave the nucleus but instead usage an intermediary to connect with the remainder of the cell. This intermediary is the messenger RNA (mRNA). Other species of RNA—like rRNA, tRNA, and also microRNA—are affiliated in protein synthesis and its regulation.

DNA and also RNA are made up of monomers that scientists contact nucleotides. The nucleotides combine with each various other to form a polynucleotide, DNA or RNA. Three components make up each nucleotide: a nitrogenous base, a pentose (five-carbon) sugar, and a phosphate group ((Figure)). Each nitrogenous basic in a nucleotide is attached to a street molecule, i beg your pardon is attached to one or much more phosphate groups.

Three components comprise a nucleotide: a nitrogenous base, a pentose sugar, and one or much more phosphate groups. Carbon residual water in the pentose are numbered 1′ v 5′ (the element distinguishes this residues native those in the base, which are numbered without utilizing a prime notation). The base is attached come the ribose’s 1′ position, and also the phosphate is attached to the 5′ position. When a polynucleotide forms, the just arrived nucleotide’s 5′ phosphate attaches come the 3′ hydroxyl group at the finish of the farming chain. Two varieties of pentose space in nucleotides, deoxyribose (found in DNA) and ribose (found in RNA). Deoxyribose is comparable in structure to ribose, but it has actually an H instead of an oh at the 2′ position. We deserve to divide bases right into two categories: purines and pyrimidines. Purines have a twin ring structure, and also pyrimidines have actually a single ring.


Only certain types of base pairing room allowed. Because that example, a specific purine have the right to only pair v a specific pyrimidine. This means A have the right to pair through T, and also G have the right to pair through C, as (Figure) shows. This is the base complementary rule. In other words, the DNA strands are complementary to each other. If the succession of one strand is AATTGGCC, the security strand would have actually the sequence TTAACCGG. Throughout DNA replication, each strand duplicates itself, bring about a daughter DNA twin helix comprise one parental DNA strand and also a recently synthesized strand.

In a dual stranded DNA molecule, the 2 strands run antiparallel come one an additional so the one strand runs 5′ to 3′ and the other 3′ come 5′. The phosphate backbone is situated on the outside, and the bases room in the middle. Adenine forms hydrogen binding (or basic pairs) through thymine, and also guanine basic pairs through cytosine.


The mRNA is check out in sets of three bases known as codons. Each codon codes for a single amino acid. In this way, the mRNA is read and the protein product is made. Ribosomal RNA (rRNA) is a significant constituent of ribosom on i m sorry the mRNA binds. The rRNA guarantee the ideal alignment that the mRNA and the Ribosomes. The ribosome’s rRNA also has an enzymatic activity (peptidyl transferase) and also catalyzes peptide shortcut formation in between two set amino acids. Transport RNA (tRNA) is just one of the the smallest of the four species of RNA, typically 70–90 nucleotides long. That carries the correct amino mountain to the protein synthetic site. The is the base pairing in between the tRNA and mRNA that permits for the correct amino acid to insert chin in the polypeptide chain. MicroRNAs space the smallest RNA molecules and their function involves regulation gene expression through interfering with the expression of particular mRNA messages. (Figure) summarizes DNA and also RNA features.

DNA and also RNA FeaturesDNARNA
FunctionCarries hereditary informationInvolved in protein synthesis
LocationRemains in the nucleusLeaves the nucleus
StructureDouble helixUsually single-stranded
PyrimidinesCytosine, thymineCytosine, uracil
PurinesAdenine, guanineAdenine, guanine

Even despite the RNA is single stranded, most RNA species show considerable intramolecular basic pairing between complementary sequences, developing a predictable three-dimensional structure important for their function.

As you have actually learned, information flow in an biology takes ar from DNA to RNA to protein. DNA dictates the framework of mRNA in a procedure scientists call transcription, and RNA dictates the protein’s framework in a procedure scientists call translation. This is the central Dogma the Life, i beg your pardon holds true for all organisms; however, exceptions to the rule occur in connection with viral infections.

To learn more about DNA, explore the Howard Hughes medical Institute BioInteractive animations ~ above the object of DNA.

Section Summary

Nucleic acids space molecules consisted of of nucleotides that straight cellular activities such as cell division and protein synthesis. Pentose sugar, a nitrogenous base, and also a phosphate group make up each nucleotide. There room two types of main point acids: DNA and RNA. DNA dead the cell’s genetic blueprint and also passes it on from parental to offspring (in the kind of chromosomes). It has actually a double-helical structure with the two strands running in opposite directions, linked by hydrogen bonds, and complementary to every other. RNA is a single-stranded polymer created of attached nucleotides comprised of a pentose street (ribose), a nitrogenous base, and also a phosphate group. RNA is involved in protein synthesis and its regulation. Messenger RNA (mRNA) copies from the DNA, exports chin from the nucleus to the cytoplasm, and also contains details for creating proteins. Ribosom RNA (rRNA) is a part of the ribosomes at the site of protein synthesis; whereas, deliver RNA (tRNA) carries the amino acid to the site of protein synthesis. The microRNA regulates using mRNA because that protein synthesis.

(Figure) A mutation occurs, and cytosine is replaced with adenine. What influence do friend think this will have actually on the DNA structure?

(Figure) adenine is bigger than cytosine and also will not have the ability to base pair properly with the guanine top top the opposing strand. This will cause the DNA to bulge. DNA repair enzymes might recognize the bulge and replace the untrue nucleotide.

A nucleotide the DNA may contain ________.

ribose, uracil, and also a phosphate groupdeoxyribose, uracil, and also a phosphate groupdeoxyribose, thymine, and also a phosphate groupribose, thymine, and also a phosphate group


The structure blocks of main point acids space ________.

sugarsnitrogenous basespeptidesnucleotides


How go the double helix structure of DNA support its function in encoding the genome?

The sugar-phosphate backbone provides a template for DNA replication.tRNA pairing with the theme strand creates proteins encoded by the genome.Complementary base pairing creates a an extremely stable structure.Complementary basic pairing permits for easy modifying of both strands the DNA.


Critical thinking Questions

What room the structural differences in between RNA and also DNA?

DNA has actually a double-helix structure. The sugar and the phosphate space on the exterior of the helix and also the nitrogenous bases space in the interior. The monomers that DNA room nucleotides containing deoxyribose, one of the four nitrogenous bases (A, T, G and also C), and also a phosphate group. RNA is typically single-stranded and is do of ribonucleotides the are linked by phosphodiester linkages. A ribonucleotide includes ribose (the pentose sugar), among the four nitrogenous bases (A,U, G, and C), and also the phosphate group.

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The four varieties of RNA room messenger RNA, ribosom RNA, transfer RNA, and also microRNA. Messenger RNA carries the details from the DNA that controls every cellular activities. The mRNA binding to the ribosomes that are constructed of proteins and rRNA, and tRNA move the exactly amino acid to the website of protein synthesis. MicroRNA regulates the accessibility of mRNA because that translation.


deoxyribonucleic acid (DNA)double-helical molecule the carries the cell’s hereditary informationmessenger RNA (mRNA)RNA that carries info from DNA to ribosomes throughout protein synthesisnucleic acidbiological macromolecule the carries the cell’s hereditary blueprint and carries instructions for the cell’s functioningnucleotidemonomer of nucleic acids; contains a pentose sugar, one or an ext phosphate groups, and a nitrogenous basephosphodiesterlinkage covalent chemistry bond the holds together the polynucleotide chains v a phosphate group linking bordering nucleotides’ 2 pentose sugarspolynucleotidelong chain that nucleotidespurinetype the nitrogenous base in DNA and also RNA; adenine and guanine room purinespyrimidinetype that nitrogenous basic in DNA and also RNA; cytosine, thymine, and also uracil are pyrimidinesribonucleic acid (RNA)single-stranded, often internally basic paired, molecule the is affiliated in protein synthesisribosomal RNA (rRNA)RNA the ensures the ideal alignment that the mRNA and the ribosomes during protein synthesis and catalyzes creating the peptide linkagetranscriptionprocess with which messenger RNA develops on a layout of DNAtransfer RNA (tRNA)RNA the carries activated amino acids to the site of protein synthetic on the ribosometranslationprocess v which RNA directs the protein’s formation