What is DNA (Deoxyribonucleic Acid) & Structure of DNA
Are you wondering you and your siblings are similar to your parents? Who is responsible for transferring Genetic material? What is DNA? All your questions will be answered in our this article. Let’s start with understanding what is DNA;
WHAT IS DNA (Deoxyribonucleic Acid)?
DNA stands for Deoxyribonucleic Acid. DNA is an organic compound that is responsible for transmitting the hereditary materials or the genetic instructions from parents to offspring.
Now before moving to functions of DNA and its working, first lets discuss the Structure of DNA.
STRUCTURE OF DNA
The structure of DNA is a double – helix structure as proposed by Watson and Crick. DNA double helix is composed of two Right-handed helical polynucleotide chains coiled around the same central axis. The 2 polynucleotide chains comprise the sugar and phosphate group that form the backbone and the nitrogenous bases project inside the helix. Nitrogen bases on the opposite strands are connected through hydrogen bonds forming base pairs (bp). 2 hydrogen bonds are formed between A and T and 3 are formed between C and G.
The two polynucleotide chains have anti-parallel polarity i.e. one strand has 5′ → 3′ polarity, and the other has 3′ → 5′ polarity. The diameter of the DNA double helix is 2nm and it repeats at an interval of 3.4nm which corresponds to 10 base pairs. DNA coils up, forming chromosomes to transmit genetic material. Human Beings have around 23 pairs of chromosomes in the nucleus of cells and each chromosome contains a single molecule of DNA.
Nucleic acids and DNA specifically, are key macromolecules for the coherence of life. DNA bears the inherited data that is given from guardians to youngsters, giving guidelines to how (and when) to make the numerous proteins expected to assemble and keep up working cells, tissues, and living beings.
DNA and RNA are polymers (on account of DNA, regularly extremely long polymers), and are comprised of monomers known as nucleotides. At the point when these monomers join, the subsequent chain is known as a polynucleotide (poly-= “many”).
Every nucleotide is comprised of three sections: a nitrogen-containing ring structure called a nitrogenous base, a five-carbon sugar, and at any rate one phosphate gathering. The sugar particle has a focal situation in the nucleotide, with the base appended to one of its carbons and the phosphate gathering (or gatherings) joined to another. We should take a gander at each piece of a nucleotide thus.
The nitrogenous bases of nucleotides are natural (carbon-based) atoms comprised of nitrogen-containing ring structures.
DNA consists of 4 Nitrogen Bases –
- Adenine (A),
- Thymine (T),
- Cytosine (C), and
- Guanine (G)
Adenine and guanine are purines, implying that their structures contain two melded carbon-nitrogen rings. Cytosine and thymine, conversely, are pyrimidines and have a solitary carbon-nitrogen ring. As appeared in the figure over, each base has an interesting structure, with its own arrangement of utilitarian gatherings connected to the ring structure.
Notwithstanding having marginally various arrangements of bases, DNA and RNA nucleotides likewise have somewhat various sugars. The five-carbon sugar in DNA is called deoxyribose, while in RNA, the sugar is ribose. These two are fundamentally the same as in structure, with only one distinction: the second carbon of ribose bears a hydroxyl gathering, while the comparable carbon of deoxyribose has hydrogen. The carbon iotas of a nucleotide’s sugar atom are numbered as 1′, 2′, 3′, 4′, and 5′ (1′ is perused as “one prime”) as appeared in the figure above. In a nucleotide, the sugar possesses a focal situation, with the base appended to its 1′ carbon and the phosphate gathering (or gatherings) joined to its 5′ carbon.
Nucleotides may have a solitary phosphate gathering, or a chain of up to three phosphate gatherings, connected to the 5′ carbon of the sugar.
In a cell, a nucleotide going to be added to the furthest limit of a polynucleotide chain will bear a progression of three phosphate gatherings. At the point when the nucleotide joins the developing DNA or RNA chain, it loses two phosphate gatherings. In this way, in a chain of DNA or RNA, every nucleotide has only one phosphate gathering.
An outcome of the structure of nucleotides is that a polynucleotide chain has directionality – that is, it has two closures that are not quite the same as one another. At the 5′ end or start, of the chain, the 5′ phosphate gathering of the main nucleotide in the chain stands out. At the opposite end, called the 3′ end, the 3′ hydroxyl of the last nucleotide added to the chain is uncovered. DNA successions are typically written in the 5′ to 3′ heading, implying that the nucleotide at the 5′ end starts things out and the nucleotide at the 3′ end comes last.
As new nucleotides are added to a strand of DNA or RNA, the strand develops at its 3′ end, with the 5′ phosphate of an approaching nucleotide connecting to the hydroxyl bunch at the 3′ finish of the chain. This makes a chain with each sugar joined to its neighbors by a lot of bonds called a phosphodiester linkage.
FUNCTIONS OF DNA
Nucleic acids, macromolecules made out of units called nucleotides, come in two normally happening assortments: deoxyribonucleic corrosive (DNA) and ribonucleic corrosive (RNA). DNA is the hereditary material found in living beings, right from single-celled microorganisms to multicellular warm-blooded creatures like you and me. Some infections use RNA, not DNA, as their hereditary material, however isn’t viewed as alive (since they can’t imitate without assistance from a host).
In eukaryotes, for example, plants and animals, DNA is found in the core, a specific, film bound vault in the cell, just as in certain different kinds of organelles, (for example, mitochondria and the chloroplasts of plants). In prokaryotes, for example, microscopic organisms, the DNA isn’t encased in a membranous envelope, in spite of the fact that it’s situated in a particular cell district called the nucleotide.
In eukaryotes, DNA is normally separated into various long, direct pieces called chromosomes, while in prokaryotes, for example, microbes, chromosomes are a lot littler and regularly roundabout (ring-formed). A chromosome may contain a huge number of qualities, each giving guidelines on the best way to make a specific item required by the cell.
Now, as you get to know about the Structure of DNA and Functions of DNA, now let’s understand the Properties of DNA;
PROPERTIES OF DNA
Deoxyribonucleic corrosive, or DNA, chains are normally found in a twofold helix, a structure where two coordinating (reciprocal) chains are remained together, as appeared in the chart at left. The sugars and phosphates lie outwardly of the helix, shaping the foundation of the DNA; this segment of the atom is some of the time called the sugar-phosphate spine. The nitrogenous bases stretch out into the inside, similar to the means of a flight of stairs, two by two; the bases of a couple are bound to one another by hydrogen bonds.
The two strands of the helix run in inverse ways, implying that the 5′ end of one strand is combined up with the 3′ end of its coordinating strand. (This is alluded to as antiparallel direction and is significant for the duplicating of DNA.)
Things being what they are, can any two bases choose to get together and structure a couple in the twofold helix? The appropriate response is a clear no. As a result of the sizes and practical gatherings of the bases, base matching is exceptionally explicit: A can just combine with T, and G can just combine with C, as demonstrated as follows. This implies the two strands of a DNA twofold helix have an entirely unsurprising relationship to one another.
For example, in the event that you realize that the succession of one strand is 5′- AATTGGCC-3′, the reciprocal strand must have the arrangement 3′- TTAACCGG-5′. This permits each base to coordinate with its accomplice:
These two strands are corresponding, with each base in one adhering to its accomplice on the other. The A-T sets are associated with two hydrogen bonds, while the G-C sets are associated with three hydrogen bonds.
5′- AATTGGCC-3′ 3′- TTAACCGG-5′
These two strands are integral, with each base in one adhering to its accomplice on the other. The A-T sets are associated with two hydrogen bonds, while the G-C sets are associated with three hydrogen bonds.
At the point when two DNA arrangements coordinate along these lines, with the end goal that they can adhere to one another in an antiparallel manner and structure a helix, they are supposed to be integral.
Hydrogen holding between integral bases holds DNA strands together in a twofold helix of antiparallel strands. Thymine structures two hydrogen bonds with adenine, and guanine structures three hydrogen bonds with cytosine.
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