The DNA Double Helix Structure was proposed by James Watson and Francis Crick in the year 1953 based on the X-rays diffraction pattern of Maurice Wilkins and Rosalind Franklin.
The DNA Double Helix is the structure of the DNA molecule as found in the living organisms. This consists of Nitrogenous Base, Deoxy-ribose Pentose sugar, and Phosphate group.
The double helix structure of DNA has two strands separated from each other. The distance between the two strands is just 2 nm.
The two strands wind around each other like a twisted ladder and is very useful in the super-coiling of DNA and make it more stable.
Each strand has the backbone composed of alternating groups of deoxy pentose sugar and phosphate groups. Attached to each sugar is one of four bases: adenine (A), cytosine (C), guanine (G), or thymine (T).
Let’s know about the advantages of the DNA Double Helix Structure…
- Here are the 6 Biological Advantages of the DNA Double Helix Structure:
Here are the 6 Biological Advantages of the DNA Double Helix Structure:
1. It allows the DNA to be tightly packed into chromosomes
One huge advantage of this Double Helix Structure of DNA is that it can wrap around itself to form supercoiled structures. This saves a lot of space for other biological activities to take place in the cell together with carrying a lot of genetic information as well.
DNA topoisomerases are universal enzymes found in all cell types from viruses to man. These enzymes act to regulate DNA supercoiling by catalyzing the winding and unwinding of DNA strands.
In each living human cell’s nucleus, there is DNA of 3 metre length. This allows the 7 billion base pairs of the DNA in each diploid cell to fit into space of just 6 microns across.
The DNA double helix in every cell is very tightly bound to an equal mass of histone proteins, which forms a repeating array of DNA-protein particles called nucleosomes. The nucleosomes are further packaged (coiled) to form a fiber of various nucleosomes.
This nucleosome fiber is further coiled to form a chromatid thread of a chromosome. In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46.
Thus, the double helix structure of the DNA can coil and super-coil of its own to fit within a size inside the living cell’s nucleus. This allows the DNA to be tightly packed inside the chromosome.
This packaging is done to compress and squeeze the 3 metre long DNA and fit it inside the nucleus.
DNA is so compressible that a DNA helix with a diameter of 2nm (2 x 10-9 m) can be supercoiled to become a chromatid of 700nm (700 x 10-9 m) diameter or so.
2. It facilitates proper self-replication
Another important advantage of the DNA double helix is that DNA can replicate itself because of its complementary base pairing between the two strands of polynucleotide chains. This ensures that when the DNA strands separate to replicate an exact copy is created.
Yes, the DNA is self-replicating as stated in the Central Dogma of Biology. The Double Helix DNA structure allows the DNA to replicate itself very smoothly.
And whenever there is a need for replication a part of the DNA get’s uncoiled and when replication has successfully taken place that DNA again supercoils itself with ease. The structure helps it to do so.
When self-replication takes place, the DNA uncoils and then the two strands of DNA separate and each strand behaves as a template for the synthesis of a new complementary strand. This is also called Semi Conservative DNA Replication Model.
It’s said that new complementary strand is produced. This means that the base pairing of the template strand with the newly synthesized strand is complementary in nature i.e. Adenine of the template strand is joined with Thymine of the new strand and that Guanine joins with Cytosine.
After the replication has taken place, that part of the DNA again supercoils and takes a compressed shape.
3. It facilitates proper transcription to mRNA
The double helix structure arranges DNA in such a way that it has a template (non-coding) strand and the non-template (coding) strand. The non-template (coding) strand acts to facilitate proper transcription to mRNA from the DNA. That’s another advantage.
A coding strand is a strand that contains the codons. On the contrary, the non-coding strand is the strand that contains the anti-codons.
The coding strand is the strand of DNA that has the same sequence as the mRNA transcript.
During transcription, mRNA is synthesized from the DNA coding strand by having complementary base pairing.
Just like if Adenine is there in the coding strand of DNA then the newly synthesized mRNA strand will have Uracil in its base pairs. The same way, Guanine will have Cytosine, Cytosine will have Guanine, and Thymine will have Adenine.
This base-pairing is possible because of the structure of the non-template (coding) strand of the DNA double helix that facilitates transcription to occur simultaneously and properly.
For protein synthesis, messenger RNA must be made from one strand of DNA called the template strand. The other strand, called the coding strand, matches the messenger RNA in sequence except for its use of uracil in place of thymine.
4. It makes the DNA stable
The double helix structure of the DNA molecule arranges it in such a way that it is stabilized by various physical and chemical interactions within itself and its surroundings. That is another awesome advantage.
The Van-der-Waals force, hydrogen bonds between complementary organic bases, base-stacking interactions between adjacent bases, and hydrophobic interactions between the nitrogenous bases and the surrounding sheath of water stabilizes the DNA structure.
Also according to the 2nd law of Thermodynamics, it is seen that the double helix of DNA is stable because its formation leads to an increase in entropy which is indicated by the release of heat.
This also indicates why DNA is stable upto a temperature of about 76.2°C. Above 76.2°C breakup of DNA occurs leading to a decrease in entropy as indicated by absorption of heat.
Moreover, it is also to be noted that DNA cannot be that much stable outside the living cells. It’s because the pH (salt concentration) and temperature conditions found in cells are very suitable for the DNA to take the double helix structure resulting in a net increase of entropy.
5. It doesn’t allow the DNA structure to mutate rapidly
Yes, one of the biggest advantages of DNA double helix and its stable structure is that it simply doesn’t allow the DNA to mutate very rapidly. The DNA proofreading and repair mechanisms save it from being mutated as well if somehow mutation has occurred.
The mutation is a permanent alteration in the DNA base sequence, such that the sequence differs from what is found in most people or from its parents.
Mutations in the base sequence have resulted from errors that occur during DNA replication. Physical and chemical factors like UV rays, exposure to alkylating agents such as Ethylmethane sulfonate and N-methyl-N-nitrosourea can also result in mutation.
But the various forces like hydrogen bonds formed between the base pairs, Van-der-Waals force, hydrophobic and hydrophilic interactions, etc. make the DNA strand more stable causing the increase in entropy.
Thus, the various chemical and physical factors must-have factors responsible to provide enough heat to the DNA structure so that its interactions can break leading to a decrease in entropy. This happens very rarely as the DNA is very stable.
If anyhow, mutations in the base sequence of the DNA have occurred from various errors during DNA replication then, there is the DNA polymerase enzyme that will proof-read to detect any wrong nucleotide sequence.
If any wrong sequence is detected, it will remove and replace the nucleotide right away, before continuing with DNA synthesis.
6. It makes DNA water soluble in nature
Thermodynamically DNA is a hydrophilic molecule meaning that it can stay with close interaction with water. The majority content inside the cell is water so the DNA being water-soluble in nature is very essential. This is one of the advantage of DNA double helix structure.
We know that the double helix of the DNA arranges itself into forming a structure where the sugar-phosphate backbone remains outside and the center of the DNA consists of various nitrogenous bases.
The sugar-phosphate backbone of the structure makes DNA negatively charged. The negative charge of the backbone, along with the (OH) groups on the deoxyribose sugar, means that the backbone is Hydrophilic as water can form hydrogen bonds with it.
On the other hand, the center of the DNA molecule is hydrophobic due to the lack of charge in DNA bases. Such hydrophobic and hydrophilic interaction with water balances the structure of DNA inside the cells.
The hydrophilic outer and hydrophobic inner of the DNA molecule make that DNA soluble in water. That’s how the rule of life is.
Moreover, scientists have also discovered that water molecules surround DNA only in a specific way by avoiding the interactions with the center part of the DNA which is hydrophobic.
Scientists have also discovered that the texture of this hydration shell depends on the water content and, actually influences the structure of the genetic substance itself.