Who Discovered the Monomers of Nucleic Acids

Who Discovered the Monomers of Nucleic Acids

In this explainer, we will learn how to draw the structure of nucleotides and nucleic acids and outline their importance in living organisms.

Nucleic acids are a type of macromolecule adjusted to storing and transferring information. Nucleic acids got their proper noun considering they were initially discovered in the nucleus of the cell. There are two types of nucleic acids: Deoxyribonucleic acid, or deoxyribonucleic acrid, and RNA, or ribonucleic acid. Even though they were initially discovered in the nucleus of eukaryotic cells, nucleic acids exist in all living things including prokaryotes, which practice not possess a nucleus at all.

Central Term: Nucleic Acid

Dna and RNA are nucleic acids. They are polymers made up of nucleotide monomers. These macromolecules are adapted to storing and transmitting genetic information.

Nucleic acids are polymers. This means that they are large molecules that are fabricated up of several repeating molecular subunits, or monomers. The monomers of nucleic acids are chosen nucleotides. A nucleotide is fabricated of 3 parts: a phosphate group, a pentose saccharide, and a nitrogen-containing base. The basic construction of a nucleotide is shown in Figure 1.

Central Term: Nucleotide

A nucleotide is a monomer of a nucleic acrid polymer. Nucleotides consist of a pentose carbohydrate, a phosphate grouping, and a nitrogen-containing base.

Example 1: Identifying the Monomer Units in Nucleic Acid Polymers

Nucleic acids are polymers. What are the monomer units of nucleic acids?


A polymer is a big molecule made up of several smaller, similar molecules bonded together. Nucleic acids include Deoxyribonucleic acid and RNA, and while they have some differences, they are both big molecules formed from strands of smaller molecules chosen nucleotides. A nucleotide consists of a phosphate group, one nitrogenous base, and a pentose saccharide. The diagram provided shows a basic outline of the construction of DNA, with i of its nucleotides highlighted.

Using this information and the diagram, we can conclude that the monomer units of nucleic acids are nucleotides.

Pentose sugars are sugar molecules that possess v atoms of carbon (“pent-” is a prefix that ways “five”). There are ii types of pentose sugars found in nucleic acids: deoxyribose carbohydrate and ribose sugar. We can tell by the names that
deoxyribose sugar is in
DNA and
ribose sugar is in
RNA. A diagram of deoxyribose and ribose sugar is shown in Figure 2.

Key Term: Pentose Sugar

A pentose sugar is a sugar molecule that contains five atoms of carbon. The pentose sugar in DNA is deoxyribose carbohydrate, and the pentose sugar in RNA is ribose sugar.

There are 5 types of nitrogenous bases: adenine, thymine, cytosine, guanine, and uracil. These are often represented by their initials: A, T, C, G, and U. The base thymine is only found in nucleotides of Dna and the base uracil is only found in nucleotides of RNA.

In the bond that exists between a nitrogenous base and a pentose carbohydrate, either ribose sugar or deoxyribose sugar, the nitrogenous base of operations is bonded to carbon number 1. The phosphate group is bonded with carbon number five. A diagram of the 5 nitrogenous bases is shown in Effigy iii.

The polymerization of nucleotides joins them together into a nucleic acid. Side by side nucleotides bond in a chemical reaction called a condensation reaction, also referred to as a dehydration synthesis reaction. A covalent bond forms between the phosphate group of one nucleotide and the pentose carbohydrate of another, releasing a molecule of water in the process. The covalent bond that is formed betwixt a phosphate group and two sugars is called a phosphodiester bond. These potent bonds form a stable structural chain that is referred to every bit a sugar–phosphate backbone. A diagram illustrating this process is shown in Figure four.

Primal Term: Sugar–Phosphate Courage

The sugar phosphate backbone describes the strand of alternating, bonded pentose sugars and phosphate groups which give a nucleic acid its structural footing.

Definition: Phosphodiester Bail

A phosphodiester bond is the chemic bond that forms between a phosphate group and 2 sugar molecules.

Nucleic acids are responsible for storing and transferring genetic information. Since the sugar–phosphate courage of a nucleic acid is ever the same, the genetic information is in the sequence, or order, of the dissimilar nitrogen-containing bases.

DNA is specifically adapted to storing data and to passing information on to offspring cells or organisms. In fact, ane chromosome can carry almost
250 MB
of information. That may not seem similar very much, but the information in Deoxyribonucleic acid is what makes you who you are. This means that the data stored in Deoxyribonucleic acid has to exist stable, accurate, and easy to copy.

Dna is made of 2 strands of nucleotides bonded together at their nitrogen-containing bases. The bases are held together with hydrogen bonds. Because of the structure of the nucleotides, DNA forms a twisted ladder shape called a double helix. The sugar–phosphate backbones brand upwards the sides of the ladder, and two hydrogen-bonded bases make upward each rung. A diagram of the double helix structure is shown in Figure 5.

Definition: Deoxyribonucleic acid (Deoxyribonucleic Acid)

DNA is the molecule that carries the genetic instructions for life. It is composed of two strands of deoxyribonucleotides that coil effectually each other to form a double helix.

The sequence of bases is the genetic information that is stored in a molecule of Deoxyribonucleic acid. Since the sequence is and then important, it has to be maintained in the correct order. We read the bases forth a strand of DNA from the
(five prime) to the
(three prime) direction. This direction is determined past the location of the third and fifth carbon atoms in the pentose sugar inside each nucleotide, which y’all can run into in Figure 2 and Effigy 4. The complementary strand faces the contrary direction, from

v .
We telephone call this arrangement “antiparallel.” We can see the antiparallel strands of DNA in Figure 5 and Figure 6.

The bases follow certain rules when bonding with each other. In Dna, adenine just bonds with thymine, and cytosine but bonds with guanine. We call these the “base pairing rules.” If we look at Figure 5 and Figure half dozen, we tin see that, in the DNA molecule, A is always paired with T, and C is always paired with G. The ii strands of base of operations-paired nucleotides are called “complementary,” because they fit together like ii puzzle pieces.

Example ii: Recalling the Type of Bond That Forms between Complementary Base of operations Pairs in Deoxyribonucleic acid

What type of bond forms between complementary base pairs in DNA?


DNA is the genetic textile of humans and is incredibly of import in determining our characteristics. I molecule of DNA is made of two complementary strands that twist into a distinct shape called a double helix. The strands are formed by the polymerization of nucleotides. Nucleotide monomers join to form nucleic acid polymers through condensation reactions that form phosphodiester bonds between the phosphate groups and pentose sugars. This creates a stable structure we call a “sugar–phosphate backbone.” The two complementary strands are held together by chemical bonds betwixt the nitrogenous bases, and only certain pairs of bases are able to bond with each other. In DNA, the nitrogenous base of operations adenine bonds with thymine, and cytosine bonds with guanine—these are the “complementary base pairs.” The nitrogenous bases which are able to bond together form hydrogen bonds that concur the 2 strands together and allow them to twist into a double helix.

So, the blazon of bail that forms betwixt complementary base of operations pairs in DNA is the hydrogen bail.

Example 3: Composing a Complementary Sequence to a Strand of DNA

In a molecule of Deoxyribonucleic acid, adenine binds to thymine, whereas guanine binds to cytosine. If a unmarried strand of Deoxyribonucleic acid has the sequence

five three A T T A T T G C K C ,
on the complementary strand, what should the sequence of Deoxyribonucleic acid bases be?


The complementary strands of DNA are antiparallel, significant they face in opposite directions. So, if left to right is from
on ane strand, then left to right would be from
on the complementary strand. DNA sequences are based on the order of the nitrogenous bases in the strand of nucleotides. Each nitrogenous base only bonds with its complementary pair. In Deoxyribonucleic acid, adenine (A) but bonds with thymine (T), and cytosine (C) only bonds with guanine (G). So, for each “A” in the sequence given in the question, we should identify a “T” on the complementary strand. For each “C” we need to place a “G,” for each “T” an “A,” and for each “G” a “C.”

Therefore, using these base of operations pairing rules, nosotros tin make up one’s mind that the sequence of DNA on the complementary strand should be TAATAACGCG.

The hydrogen bonds between the two nucleotide strands are relatively easy to break, and the nucleotide bases will only bond with a complementary match. These traits of Deoxyribonucleic acid are what enable it to conduct big amounts of information and to be copied quickly and precisely. Dna is also an specially stable molecule. This is what makes Dna well adapted to its office of storing hereditary information.

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The base pairing rules we have described are oft chosen “Chargaff’s rules” subsequently the scientist who adult them. A pharmacist named Erwin Chargaff discovered in the 1940s that, in a sample of DNA from any species, the concentration of adenine bases will be equal to the concentration of thymine. Too, the concentration of cytosine volition be equal to the concentration of guanine. This discovery is what led to the base pairing rules nosotros have already described.

This information can also exist used to calculate the percent composition of the different bases of a sample of Deoxyribonucleic acid. When provided with the full number of nucleotides in a sample and the quantity of just i type of base, we can use Chargaff’south rules to make up one’s mind the composition of all 4 unlike varieties of nitrogenous bases.

How To: Calculating Percent Limerick of Nitrogenous Bases Using Chargaff’s Rules (Base Pairing Rules)

The base pairing rules for Dna land that, between the two complementary strands, adenine always pairs with thymine and cytosine always pairs with guanine. This is illustrated in the diagram below.

Relatedly, we can infer that, in any sample of DNA, the number of adenine bases will be equal to the number of thymine bases, and the number of cytosine bases will be equal to the number of guanine bases.

This information can be used to calculate the number of the bases and the percent composition of each type of base in a sample of Dna with very lilliputian initial data.

Let’s telephone call the full number of bases

B t o t a l .

We will call the number of bases for each type of nucleotide

B A ,

B T ,

B C ,
for the number of bases of adenine, thymine, cytosine, and guanine respectively.

Using Chargaff’southward rule, we know that
B B A T = ,
and also
B B C G = ,
and finally that
B B B B B t o t a l A T C G = + + + .

Let’s employ this knowledge to an example.

In the diagram above, the expanded segment possesses 12 base pairs.

Since there are 12 pairs, at that place are 24 full bases:
B t o t a 50 = two 4 .

Let’south say that nosotros are told that 4 of these bases are cytosine:
B C = 4 .


B B C One thousand = ,

B Chiliad = 4 .

Side by side, we can figure out the number of bases remaining after we accept excluded those that are cytosine and guanine:
B B B B B t o t a l A T C G = + + +
2 four = + + four + iv 2 4 = + + 8 2 4 8 = + + viii 8 1 six = + . B B B B B B B B A T A T A T A T

This prepare of calculations tells u.s.a. that the number of bases remaining after we have excluded those that are cytosine and guanine is 16.

Since, according to Chargaff’s rule,
B B A T = ,
nosotros tin can conclude that one-half of the remaining 16 bases are adenine and half are thymine:
i 6 = + = + = 2 i 6 = 2 1 6 2 = two 2 8 = . B B B B B B B B A T A A A A A A

And, since

B B A T = ,

B T = 8 .

Nosotros can bank check these values past comparison them to what nosotros see in the diagram. Nosotros count the number of A, T, C, and G to check our work.

Now, nosotros know the number of each type of base of operations nowadays in our sample of 24 total bases; allow’southward calculate the percent limerick of each.

To summate the percent, we volition separate the number of a detail base by the total number of bases and multiply that value past

one % .

For case,
% = × 1 % . B B B A A T O T A 50

If nosotros complete this calculation for each of the bases, nosotros go the information in the table below.

Base Number Percentage
Adenine viii 3 3 . 3 %
Thymine 8 three 3 . iii %
Cytosine four 1 6 . 7 %
Guanine 4 1 6 . 7 %

If we start with the total number of nucleotides and the number of only one blazon of base of operations, we can summate the number and the percent composition of each of the four bases in a sample of Deoxyribonucleic acid.

Case 4: Calculating Pct Limerick of Nucleotide Bases in Deoxyribonucleic acid

A DNA molecule contains 180 bases. 18 of these bases are adenine.

  1. What percentage of the bases are thymine?
  2. What percentage of the bases are guanine?


Function 1

This question presents us with some information about a section of a Deoxyribonucleic acid molecule. Nosotros are starting time told that the molecule contains 180 bases. Nosotros are also informed that of those 180 bases, 18 are adenine.

A molecule of DNA consists of two complementary strands. Complementary ways that the 2 strands fit together according to a pattern. In this instance, that pattern is what is known every bit the “base pairing rules.” The base pairing rules land that where a strand of DNA possesses the base adenine, the complementary strand volition have the base thymine. Too, where at that place is a guanine base on one strand, the complementary strand will have cytosine. The illustration of Deoxyribonucleic acid shown below provides an case of these base pairing rules in activity.

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Knowing this, we can conclude that if there are eighteen adenine bases in a section of Deoxyribonucleic acid, there will also be 18 thymine bases, since every adenine would be paired with a thymine. The question asks about the percentage of the thymine bases.

To convert the number to the percentage, nosotros must take the number of a particular base, divide it by the full number of bases, and then multiply that value by

1 % :

ane 8 1 8 × 1 % = 1 % . t h y thou i n e t o t a l b a south east s

Part 2

Now we have the total number of bases, the number of adenine bases, and the number of thymine bases. Using these numbers, we can summate the number of guanine and cytosine bases:
1 8 ( 1 8 + 1 eight ) = 1 four 4 . t o t a fifty b a southward e south a d eastward north i due north east t h y m i due north e c y t o south i northward e a n d chiliad u a north i n e

The same rules apply to the bases cytosine and guanine every bit the ones nosotros have used for adenine and thymine. Of the 144 remaining bases, since cytosine and guanine are complementary pairs, exactly half will be cytosine and one-half will be guanine:
1 four iv ii = 7 2 . c y t o s i north e a northward d g u a due north i n e c y t o s i n e o r g u a north i n east

Using the to a higher place calculations, nosotros can make up one’s mind that 72 bases volition be cytosine and 72 will exist guanine.

Once again, the question asks nearly the percentage of guanine, non its number. To obtain this value, we must split up the number of guanine bases past the total number of bases, then multiply the resulting value by

i % :

7 ii 1 8 × 1 % = iv % . g u a n i northward e t o t a l b a s due east s

Deoxyribonucleic acid and RNA molecules serve dissimilar functions in living cells. Deoxyribonucleic acid stores genetic information and RNA copies that information to carry it from identify to place. RNA specifically carries the genetic code from the Deoxyribonucleic acid in the nucleus to the parts of the cell responsible for protein synthesis.

In order for this to happen, the ii strands of Dna dissever and RNA nucleotides pair with the exposed Dna bases, forming a single strand of data that tin exist transferred elsewhere. This is shown in Figure vii.

When RNA copies information from Deoxyribonucleic acid, it follows a similar set of base pairing rules. Cytosine and guanine pair as usual. Wherever DNA has thymine, information technology volition pair with the RNA base adenine, but where DNA has adenine, information technology will pair with the RNA base of operations uracil instead of thymine. This is illustrated in Figure 8 and Tabular array 1.

Fundamental Term: RNA (Ribonucleic Acid)

RNA is a single-stranded polynucleotide that is specifically adapted for the transmission of genetic information from place to place.

Tabular array 1: The base pairing rules for Dna and for RNA.

DNA Base of operations (Template) Complementary DNA Base Complementary RNA Base
Adenine Thymine Uracil
Thymine Adenine Adenine
Cytosine Guanine Guanine
Guanine Cytosine Cytosine

Case v: Contrasting the Types of Nitrogenous Bases in Deoxyribonucleic acid and RNA

What nitrogenous base of operations in Dna is replaced by uracil in RNA?


Both DNA and RNA are nucleic acids. Nucleic acids are polymers fabricated up of nucleotide monomers. A nucleotide is a molecule made of a phosphate group, a pentose carbohydrate, and a nitrogen-containing base. There are 5 kinds of nitrogenous bases: adenine, thymine, cytosine, guanine, and uracil. Both Dna and RNA nucleotides possess adenine, cytosine, or guanine bases. Only DNA possesses the base thymine, and only RNA possesses the base uracil. This means that, during base pairing, an adenine base would have the complementary pair thymine in a molecule of Dna but would pair with uracil in RNA.

Therefore, nosotros can determine that the nitrogenous base in DNA that is replaced by uracil in RNA is thymine.

Nucleic acids are the molecules that tell cells what they are, what cellular machinery to build, and how to build it. The adaptations of nucleic acids brand them especially suited to their role in information storage and transfer.

Let’s summarize what nosotros accept learned in this explainer.

Key Points

  • Nucleic acids are biological macromolecules adjusted to storing and transferring information.
  • Nucleic acids are polymers made up of monomers called nucleotides.
  • A nucleotide is a molecule that consists of a phosphate group, a pentose sugar, and 1 of five nitrogenous bases.
  • The nitrogenous bases present in DNA are adenine, thymine, cytosine, and guanine, while RNA has the base uracil instead of thymine.
  • Deoxyribonucleic acid is adapted to storing information, is a double-stranded molecule, and possesses deoxyribose sugar.
  • RNA is adjusted to transferring information, is a single-stranded molecule, and possesses ribose carbohydrate.

Who Discovered the Monomers of Nucleic Acids

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