What are the 3 major components of DNA?

Question

What are the 3 major components of DNA?

Answer 1

SUGAR

The sugar in DNA is deoxyribose. The sugar in RNA is r ibose. The deoxy- prefix indicates that this form of the sugar contains one less oxygen atom. The 2-carbon of the pentose sugar has two hydrogens attached to it instead of an hydrogen and hydroxyl (-OH).

This is shown in the diagram below, and in the structural images which can be loaded into the frame on the left using the button above. Remember that the rotatable images in the frame on the left do not show the hydrogen atoms.

NITROGENOUS BASES

There are three pyrimidine bases, and each consists of a 6-member ring containing both nitrigen and carbon atoms. Two pyrimidines, Thymine

and Cytosine , are found in DNA. RNA also contains two pyrimidine

PURINES

Again, the purines are made from two heterocyclic rings of carbon and nitrogen. This time, a 6-member and a 5-member ring have fused. There are two purines, Adenine

and Guanine , and both are found in DNA and RNA.

The purines are joined by their N9 atom to the 1' carbon of deoxyribose. The nucleosides formed are deoxyadenosine

and deoxyguanosine. The bases are known as A and

Answer 2

A DNA contains linked nucleotide bases, and these nucleotide bases each have 3 components: a 5-carbon sugar, a nitrogenous base and a phosphoric acid (the phosphate group).

The 5 carbon sugar in DNA is deoxyribose.

The nitrogenous bases exist in 4 different forms in DNA, namely Adenine (A), Guanine (G), Cytosine (C), Thymine (T).

The phosphate group - which gives the nucleotide its acidic character, has the chemical formula H3PO4.

These 3 components (sugar + phosphoric acid + nitrogenous base) link up to form a nucleotide. Combining nucleotides would result in a strand of DNA (polynucleotide). This strand then "pairs up" with another strand via complementary base-pairing - Adenine to Thymine, Cytosine to Guanine.

And hence the result is a DNA double helix.

Hope the explanation works for you!

Answer 3

well if you dont wish to read a giant copy paste, the three major components would simply be a sugar, a phosphate and a base. more information is in the second paragraph of the previous post.

Answer 4

To the poster above me: Learn how to write your own answer, rather than copying and pasting.

The three major components of DNA are Nitrogenous Bases, Deoxyribose (A sugar), and a phosphate group.

Answer 5

Image a twisted ladder (that's the shape of DNA)

The groups are

1. Phosphate

2. Deoxyribose sugar

3. Nitrogen base

The phosphates and deoxyribose sugars make up the sides of the "ladder" (alternating one after the other) and nitrogen bases are the "rungs" of the ladder.

Answer 6

sugar, base, and phosphate. I can still see the page in my biology book!

Answer 7

Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. The main role of DNA molecules is the long-term storage of information. DNA is often compared to a set of blueprints or a recipe, since it contains the instructions needed to construct other components of cells, such as proteins and RNA molecules. The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information.

Chemically, DNA consists of two long polymers of simple units called nucleotides, with backbones made of sugars and phosphate groups joined by ester bonds. These two strands run in opposite directions to each other and are therefore anti-parallel. Attached to each sugar is one of four types of molecules called bases. It is the sequence of these four bases along the backbone that encodes information. This information is read using the genetic code, which specifies the sequence of the amino acids within proteins. The code is read by copying stretches of DNA into the related nucleic acid RNA, in a process called transcription.

Within cells, DNA is organized into structures called chromosomes. These chromosomes are duplicated before cells divide, in a process called DNA replication. Eukaryotic organisms (animals, plants, and fungi) store their DNA inside the cell nucleus, while in prokaryotes (bacteria and archae) it is found in the cell's cytoplasm. Within the chromosomes, chromatin proteins such as histones compact and organize DNA. These compact structures guide the interactions between DNA and other proteins, helping control which parts of the DNA are transcribed.

Physical and chemical properties

The chemical structure of DNA. Hydrogen bonds are shown as dotted lines.

The chemical structure of DNA. Hydrogen bonds are shown as dotted lines.

DNA is a long polymer made from repeating units called nucleotides.[1][2] The DNA chain is 22 to 26 Ångströms wide (2.2 to 2.6 nanometres), and one nucleotide unit is 3.3 Å (0.33 nm) long.[3] Although each individual repeating unit is very small, DNA polymers can be enormous molecules containing millions of nucleotides. For instance, the largest human chromosome, chromosome number 1, is approximately 220 million base pairs long.[4]

In living organisms, DNA does not usually exist as a single molecule, but instead as a tightly-associated pair of molecules.[5][6] These two long strands entwine like vines, in the shape of a double helix. The nucleotide repeats contain both the segment of the backbone of the molecule, which holds the chain together, and a base, which interacts with the other DNA strand in the helix. In general, a base linked to a sugar is called a nucleoside and a base linked to a sugar and one or more phosphate groups is called a nucleotide. If multiple nucleotides are linked together, as in DNA, this polymer is called a polynucleotide.[7]

The backbone of the DNA strand is made from alternating phosphate and sugar residues.[8] The sugar in DNA is 2-deoxyribose, which is a pentose (five-carbon) sugar. The sugars are joined together by phosphate groups that form phosphodiester bonds between the third and fifth carbon atoms of adjacent sugar rings. These asymmetric bonds mean a strand of DNA has a direction. In a double helix the direction of the nucleotides in one strand is opposite to their direction in the other strand. This arrangement of DNA strands is called antiparallel. The asymmetric ends of DNA strands are referred to as the 5′ (five prime) and 3′ (three prime) ends, with the 5' end being that with a terminal phosphate group and the 3' end that with a terminal hydroxyl group. One of the major differences between DNA and RNA is the sugar, with 2-deoxyribose being replaced by the alternative pentose sugar ribose in RNA.[6]

The DNA double helix is stabilized by hydrogen bonds between the bases attached to the two strands. The four bases found in DNA are adenine (abbreviated A), cytosine (C), guanine (G) and thymine (T). These four bases are attached to the sugar/phosphate to form the complete nucleotide, as shown for adenosine monophosphate.

These bases are classified into two types; adenine and guanine are fused five- and six-membered heterocyclic compounds called purines, while cytosine and thymine are six-membered rings called pyrimidines.[6] A fifth pyrimidine base, called uracil (U), usually takes the place of thymine in RNA and differs from thymine by lacking a methyl group on its ring. Uracil is not usually found in DNA, occurring only as a breakdown product of cytosine.

Major and minor grooves

Animation of the structure of a section of DNA. The bases lie horizontally between the two spiraling strands. Large version

Animation of the structure of a section of DNA. The bases lie horizontally between the two spiraling strands. Large version[9]

The double helix is a right-handed spiral. As the DNA strands wind around each other, they leave gaps between each set of phosphate backbones, revealing the sides of the bases inside (see animation). There are two of these grooves twisting around the surface of the double helix: one groove, the major groove, is 22 Å wide and the other, the minor groove, is 12 Å wide.[10] The narrowness of the minor groove means that the edges of the bases are more accessible in the major groove. As a result, proteins like transcription factors that can bind to specific sequences in double-stranded DNA usually make contacts to the sides of the bases exposed in the major groove.[11]

Base pairing

    Further information: Base pair

Each type of base on one strand forms a bond with just one type of base on the other strand. This is called complementary base pairing. Here, purines form hydrogen bonds to pyrimidines, with A bonding only to T, and C bonding only to G. This arrangement of two nucleotides binding together across the double helix is called a base pair. The double helix is also stabilized by the hydrophobic effect and pi stacking, which are not influenced by the sequence of the DNA.[12] As hydrogen bonds are not covalent, they can be broken and rejoined relatively easily. The two strands of DNA in a double helix can therefore be pulled apart like a zipper, either by a mechanical force or high temperature.[13] As a result of this complementarity, all the information in the double-stranded sequence of a DNA helix is duplicated on each strand, which is vital in DNA replication. Indeed, this reversible and specific interaction between complementary base pairs is critical for all the functions of DNA in living organisms.[1]

Top, a GC base pair with three hydrogen bonds. Bottom, an AT base pair with two hydrogen bonds. Non-covalent hydrogen bonds between the pairs are shown as dashed lines.

The two types of base pairs form different numbers of hydrogen bonds, AT forming two hydrogen bonds, and GC forming three hydrogen bonds (see figures, left). The GC base pair is therefore stronger than the AT base pair. As a result, it is both the percentage of GC base pairs and the overall length of a DNA double helix that determine the strength of the association between the two strands of DNA. Long DNA helices with a high GC content have stronger-interacting strands, while short helices with high AT content have weaker-interacting strands.[14] In biology, parts of the DNA double helix that need to separate easily, such as the TATAAT Pribnow box in some promoters, tend to have a high AT content, making the strands easier to pull apart.[15] In the laboratory, the strength of this interaction can be measured by finding the temperature required to break the hydrogen bonds, their melting temperature (also called Tm value). When all the base pairs in a DNA double helix melt, the strands separate and exist in solution as two entirely independent molecules. These single-stranded DNA molecules have no single common shape, but some conformations are more stable than others.[16]

Sense and antisense

    Further information: Sense (molecular biology)

A DNA sequence is called "sense" if its sequence is the same as that of a messenger RNA copy that is translated into protein.[17] The sequence on the opposite strand is called the "antisense" sequence. Both sense and antisense sequences can exist on different parts of the same strand of DNA (i.e. both strands contain both sense and antisense sequences). In both prokaryotes and eukaryotes, antisense RNA sequences are produced, but the functions of these RNAs are not entirely clear.[18] One proposal is that antisense RNAs are involved in regulating gene expression through RNA-RNA base pairing.[19]

A few DNA sequences in prokaryotes and eukaryotes, and more in plasmids and viruses, blur the distinction between sense and antisense strands by having overlapping genes.[20] In these cases, some DNA sequences do double duty, encoding one protein when read along one strand, and a second protein when read in the opposite direction along the other strand. In bacteria, this overlap may be involved in the regulation of gene transcription,[21] while in viruses, overlapping genes increase the amount of information that can be encoded within the small viral genome.[22]

Supercoiling

    Further information: DNA supercoil

DNA can be twisted like a rope in a process called DNA supercoiling. With DNA in its "relaxed" state, a strand usually circles the axis of the double helix once every 10.4 base pairs, but if the DNA is twisted the strands become more tightly or more loosely wound.[23] If the DNA is twisted in the direction of the helix, this is positive supercoiling, and the bases are held more tightly together. If they are twisted in the opposite direction, this is negative supercoiling, and the bases come apart