Salient Features of Double Helix Structure of DNA: Structure, Features
The silent features of the double helix of DNA explain how DNA looks and works. DNA is a double-stranded nucleic acid. The double helical structure of nucleic acid is formed as a result of its strands twisting. This DNA structure is key to inheritance and life. The silent features of the double helix of DNA were discovered with the help of Rosalind Franklin X- rays studies.
This Story also Contains
- What is DNA?
- What is DNA Double Helix Model?
- Salient Features of Double Helix Model of DNA
- Discovery of the Double Helix Model of DNA
- Structure of DNA in Double Helix Model
- Function of the Double Helix Model of DNA
- MCQs on Salient Features of Double Helix Structure of DNA
- Recommended Video On DNA Structure:
The double helix of DNA is made of nucleotides that pair together. In B-DNA, the most common double helical structure is found in nature. The helix is right-handed with about 10 bases per turn. It has a major groove and a minor groove. The Salient Features of the Double Helix Structure of DNA are studied in the chapter Molecular Basis of Inheritance in Biology.
What is DNA?
DNA( Deoxyribonucleic Acid) is a genetic material in all known living organisms and many viruses. It has instructions for the development, functioning, growth, and reproduction. The information is stored as a sequence of nucleotides.
The double helix model of DNA explains how the genetic code is stored and copied. In 1953, James Watson and Francis Crick described DNA as two strands coiled in a right‑handed helix. Each strand has nucleotides.
This double helix model of DNA shows how DNA replicates, stores, and transfers genetic information. The salient features of the double helix structure of DNA make it the foundation of molecular biology. The DNA structure is important for understanding types of mutations, repair, and advances in genetics and biotechnology.
What is DNA Double Helix Model?
The double helix structure of DNA consists of two strands twisted like a spiral. These strands run in opposite directions. This is called anti-parallel.
In the silent features of the double helix of DNA, the 5' end of one strand matches the 3' end of the second strand. It is the antiparallel orientation of the two long polymeric strands winding in a helical form. It is this antiparallel orientation in which the DNA gets replicated and functions. These two strands wind in together symphonically in a right-handed helix. When viewed along the axis Double Helix Model, it twists to the right.
DNA Double Helix Model of DNA Diagram
Given below is the structure of a DNA double helix model, showing its components
Salient Features of Double Helix Model of DNA
The double helix model of DNA explains how DNA stores genetic information. DNA has two strands twisted into a spiral. These strands are anti‑parallel and form a right‑handed helix. The salient features of double helix structure of DNA make it the foundation of molecular biology.
The salient features of double helix model of DNA:
DNA has two strands twisted into a helix.
Strands run in opposite directions (anti‑parallel).
Base pair specifically. A with T, C with G.
Purine pairs with pyrimidine, giving uniform width (2 nm).
One helix turn has about 10 base pairs.
Distance between bases is 0.34 nm.
Helix is right‑handed.
The major groove is wide, the minor groove is narrow.
Backbone is a sugar‑phosphate chain.
Structure allows replication, storage, and repair of the genetic code.
Discovery of the Double Helix Model of DNA
The discovery of the double helical structure of DNA marked one of the big breakthroughs in science, and with the discovery came the hard work of a few key scientists.
James Watson and Francis Crick:
James Watson was an American biologist, while Francis Crick was a British physicist. They are the ones behind the discovery of the double helix structure in 1953, and they proposed a model for the structure, resulting in a Nobel Prize in Physiology or Medicine in 1962, alongside Maurice Wilkins.
Contributions of Rosalind Franklin and Maurice Wilkins
Rosalind Franklin's contribution to the proceedings was in X-ray diffraction, which proved critical in showing DNA to be helical. Her famous photo 51 gives key evidence to help Watson and Crick build their model. Maurice Wilkins worked on X-ray diffraction as well as on DNA.
Structure of DNA in Double Helix Model
DNA is composed of nitrogenous bases, sugar groups, and a phosphate group. The DNA has a sugar-phosphate backbone. The basic structure of DNA has been described below:
Nucleotide Composition
DNA is composed of many nucleotides joined in a chain. Each nucleotide is a complex of three molecules:
Phosphate Group
The backbone of the DNA chain is made up of the phosphate group. The deoxyribose sugars of two nucleotides of a DNA chain are tied together by the boning of their phosphate groups to form a phosphodiester linkage.
Deoxyribose Sugar
Deoxyribose is a five-membered sugar that is a compound in DNA's backbone. A deoxyribose molecule is attached to a phosphate group and a nitrogenous base.
Nitrogenous Bases
The nitrogenous bases are adenine (A), thymine (T), cytosine (C), and guanine (G). These bases are very crucial in storing genetic information.
Function of the Double Helix Model of DNA
The double helix structure of DNA has various functions, including replication, transcription, and encoding the genetic material of the organism. Some functions are described below-
DNA Replication: The double helix structure is very functional in the accurate replication of DNA.
Semi-Conservative Replication Model: During DNA replication, the two strands that make up the double helix unwind from each other. This unwinding opens the two DNA strands and allows them to act as templates for creating new strands; thus, two new double-stranded DNA molecules are created where each molecule consists of one strand that is an original strand of DNA and one strand that is newly synthesised. This was shown experimentally by Messelson and Stahl, therefore is also known as the Meselson and Stahl experiment.
Genetic Information Storage and Transmission: It is the string of nitrogenous bases along the DNA string that carries genetic code. Such code is used to synthesise proteins that carry out several functions in a cell.
Mutation and Repair Mechanisms: Errors in the DNA sequence, or mutations, may result from both replication errors and environmental factors. The double helical structure provides the base for the identification and repair of different types of mutations through several DNA repair mechanisms, thereby maintaining the integrity of the genetic information.
MCQs on Salient Features of Double Helix Structure of DNA
Q1. The fact that a purine base is always paired through hydrogen bonds with a pyrimidine base leads to, in the DNA double helix
Option 1: the antiparallel nature
Option 2: the semi-conservative nature
Option 3: uniform width throughout DNA
Option 4: uniform length in all DNA
Correct answer: 3)uniform width throughout DNA.
Explanation:
The salient feature of the Double helix structure -
The bases in two strands are paired through hydrogen bonds (H-bonds) forming base pairs (bp). Adenine forms two hydrogen bonds with thymine from opposite strands and vice versa. This generates approximately uniform distance between the two strands of the helix.
Since specific and different nitrogen bases occur on the two DNA chains, the latter are complementary. It is because of a specific base pairing with a purine lying opposite to a pyrimidine. This makes the two chains 2 nm thick. A larger-sized purine lies opposite to the smaller-sized pyrimidine, A opposite to T and C opposite to G. This gives the uniform width throughout DNA.
Hence, the correct answer is option 3)uniform width throughout DNA.
Q2. Select the incorrect option for B-DNA.
Option 1: Two chains of DNA are coiled in right handed fashion always.
Option 2: Pitch of helix is 3.4 nm.
Option 3: 9 bp in each turn.
Option 4: Distance between two base-pair in helix is approximately 0.34 nm .
Correct answer: 3) 9 bp in each turn.
Explanation:
B-DNA is the most common and biologically significant form of DNA found in living cells. Two chains are coiled in a right-handed fashion. The pitch of the helix is 3.4 nm (nm=10-9 m) and there are roughly 10 bp in each turn. Consequently, the distance between a bp in a helix is approximately equal to 0.34 nm.
Hence, the correct answer is option 3) 9 bp in each turn.
Q3. In a DNA strand, the nucleotides are linked together by:
Option 1: Glycosidic bonds
Option 2: Phosphodiester bonds
Option 3: Peptide bonds
Option 4: Hydrogen bonds
Correct answer: 2) Phosphodiester bonds.
Explanation:
In a DNA molecule, nucleotides are joined through phosphodiester bonds, which are crucial covalent connections between the 3'-hydroxyl group of sugar in one nucleotide and the 5'-phosphate group of the sugar in the next.
This bonding pattern generates the DNA's sugar-phosphate backbone, ensuring a clear directionality from 5' to 3' ends. The significance of these bonds lies in their contribution to DNA's structural integrity and facilitation of nucleotide chain elongation.
Hence, the correct answer is option 2) Phosphodiester bonds.
Recommended Video On DNA Structure:
Frequently Asked Questions (FAQs)
The double helix structure of DNA is formed by two long chains of nucleotides coiling around each other in a spiral to form a shape. Watson and Crick proposed this structure at the beginning of 1953, after which it provided part of the basis of the genetic information during the heredity and cell function.
They explain how DNA stores genetic code, replicates accurately, and repairs mutations. This makes inheritance possible.
The double helical structure allows each strand to serve as a template for the production of a new complementary strand. In replication, the strands separate, to enable the semi-conservative process of replication wherein each DNA molecule comprises one new and one old strand.
The anti‑parallel strands separate. Each strand acts as a template. This ensures accurate copying of genetic information.
The major and minor grooves in the double-strand structure of DNA are the particular regions at which diverse proteins and molecules bind to direct replication, transcription, and repair. This allows specific interactions to act as regulators of genetic activities and maintainers of cellular functions.
