Chargaff Rule Ratio Formula

  • In this chargaff rule ratio formula post we have briefly explained about structure of DNA, molecular structure, phosphodiester bond, deoxyribonucleic acid strand, and chargaff rule ratio formula.
  • Before the 1950s, the structure of Deoxyribonucleic Acid was a mystery. James Watson (American biologist) and Francis Crick (British physicist) established the double-helix model for DNA in the early 1950s after synthesizing existing physical and chemical evidence and basing their research on their findings.
  • Watson and Crick were aided in their discovery of the double helix structure of DNA by the work of Rosalind Franklin and Maurice Wilkins. Watson and Crick’s model of Deoxyribonucleic Acid was widely accepted and is now known as Watson and Crick’s model of Deoxyribonucleic Acid.
Deoxyribonucleic Acid

James Watson and Francis Crick, crackers of the DNA code. Image Source: theguardian

Structure of DNA

  • DNA is a molecule with two strands. It’s made up of two helical chains or strands spirally wrapped around a common axis to form a twisted ladder-like right-handed double helix.
  • Each strand has two ends: a phosphate group on the 5′ end and a hydroxyl group on the 3′ end. Because the DNA strands run in opposite orientations, the 5’ends of one chain and the 3’ends of another chain are on the same side, making them antiparallel. One strand is known as sense strand and goes from 5′ to 3′, whereas the opposing strand is known as antisense strand and runs from 3′ to 5′.
  • DNA has a consistent diameter of roughly 2 nanometers. The length of each spiral turn is 3.6 nm, while the distance between each turn is 3.6 nm (earlier 3.4 nm). 0.34 nm is the distance between base pairs or two succeeding rings.
Deoxyribonucleic Acid
  • There are 10.5 nucleotides per turn, or in one complete spiral turn or 360-degree rotation (earlier 10 nucleotides).
  • Between the two chains or strands, major and minor grooves are created by the spiral arrangement of chains. The major groove is wider than the minor groove, which is narrower. When the backbones are far apart, major grooves form, and when they are close, minor grooves form.
  • On the exterior of the double helix, the deoxyribose sugar and phosphate groups alternate. As a result, it forms the helix’s backbone.
  • Adenine (A), Cytosine (C), Guanosine (G), and Thymine (T) are the four bases that make up each DNA strand (T). The complimentary bases on one strand are bound or paired with those on the opposite strand.
  • Inside the double helix are the pyrimidine (Thymine and Cytosine) and purine (Adenine and Guanine) bases.
  • Through hydrogen bonding, a certain purine base bonds or forms a pair with a specific pyrimidine base. Adenine (A) is paired with Thymine (T), and Guanine (G) is paired with Cytosine (C).
  • Guanine and Cytosine are connected by three hydrogen bonds (G=C), whereas Adenine and Thymine are bonded by two hydrogen bonds (A=T). Hydrogen bonds produced between purine and pyrimidine bases stabilise the double helix structure.
  • Complementary base pairs are the base pairs that make up the stages of the DNA ladder. As a result, the two DNA strands are complimentary. The number of A bases is the same as the number of T bases, and the number of G bases is the same as the number of C bases. As a result, the number of purine bases and pyrimidine bases is always the same. A rule known as Chargaff’s rule also suggests this.
  • The strands or sides of the helix are made up of alternating sugar and phosphate nucleotide molecules connected by a 3′-5′ phosphodiester linkage. The ladder’s steps, on the other hand, are built up of nitrogen bases linked to sugars by glycosidic connections. If we think of the double helix structure as a ladder, the sugar and phosphate groups are the sides, while the bases are the steps or rungs.

Molecular Structure

  • One of the major families of biological macromolecules is DNA, which is a nucleic acid. The DNA molecule is found in the nucleus of eukaryotic cells and has two strands that are firmly packed or coiled into a thread-like structure called chromosome. Its structure is stable because it is firmly coiled around histone proteins. Only when the cell is sinking is DNA visible under a microscope, as DNA becomes more tightly packed during cell division.
  • Nucleotides make up each strand of DNA, which contains two ends: a 5′ end and a 3′ end. The two DNA strands are antiparallel and hence run in opposite directions since DNA has an antiparallel structure.
  • So, just as a protein is made up of amino acids, DNA is made up of nucleotides. It is a collection of nucleotides that are linked together to form spirally coiled DNA strands, also known as chromosomes. DNA is made up of four distinct nucleotides. Adenine, Cytosine, Thymine, and Guanine are the nucleotides involved (A, C, T and G). A 5-carbon sugar, a phosphate group, and a nitrogenous base are the three simple molecular constituents of each nucleotide.
  • A nucleotide is formed when a phosphate group and a nitrogenous base are bound to a sugar molecule. Deoxyribose sugar, which is a cyclical molecule made up of one oxygen and four carbons organised in a ring form, is the sugar of all four nucleotides. This ring, however, has a fifth carbon atom linked to the fourth carbon. Because all nitrogenous bases tend to have numerous nitrogen atoms, they are referred to as nitrogenous bases.
  • A phosphorus atom is linked to or connected with four oxygen atoms to form the phosphate group. This phosphorus atom has a tendency to connect with other oxygen atoms, such as the oxygen atom of another nucleotide’s deoxyribose sugar.
  • The nitrogenous bases of the four nucleotides in a DNA molecule differ from one another. Because each nucleotide has a different nitrogenous base connected to its deoxyribose sugar, it is termed as follows:
  • Adenine nucleotide contains adenine
  • Thymine nucleotide contains thymine
  • Guanine nucleotide contains guanine
  • Cytosine nucleotide contains cytosine.

Phosphodiester bond

  • In a Deoxyribonucleic Acid molecule, the phosphodiester link connects the nucleotide monomers. The 3′ carbon of one nucleotide is constantly connected to the 5′ carbon of the next nucleotide by this link.

  • A covalent connection is established between the oxygen at a nucleotide’s 3′ carbon and the phosphorus atom in the phosphate group connected at the 5′ carbon of the other nucleotide in this interaction. As a result, it’s known as the 3′-5′ phosphodiester bond. Dehydration synthesis is the process of releasing a water molecule when a nucleotide meets another nucleotide. When polymers are created, this process normally occurs.

Deoxyribonucleic Acid strand

  • Non-covalent hydrogen bonds between two strands connect Deoxyribonucleic Acid strands. These bonds are generated between specific hydrogen atoms on one base (hydrogen bond donors) and specified oxygen or nitrogen atoms on the other base (hydrogen bond acceptors) on the opposite strand.
  • There is one donor and one acceptor for both adenine and thymine nucleotides. Guanine has one acceptor and two donors, while cytosine has one acceptor and two donors.
  • H bonds are always used to connect A nucleotides to T nucleotides. Cytosine nucleotides, on the other hand, are always linked to guanine nucleotides by H bonds. Complementary base pairing is a sort of selective bonding that offers stability to the nucleotide sequence of two DNA strands. The arrows point to hydrogen (h) bonds; there are two hydrogen ties between Thymine and Adenine and three hydrogen bonds between Cytosine and Guanine.

Chargaff Rule Ratio Formula

  • In the 1950s, Erwin Chargaff observed that the nitrogenous bases of nucleotides (A, T, C, and G) were not equal. It was discovered, however, that the quantity of A was equal to the quantity of T, and the quantity of C was always equal to the quantity of G. This discovery was crucial in gaining a better understanding of the Deoxyribonucleic Acid double helix model and base bonding.
  • Until now, we’ve assumed that the double helix structure is formed by two long DNA strands spiralling together. Furthermore, DNA can be broken down into tiny parts known as genes. A gene is a Deoxyribonucleic Acid segment or small portion. The DNA molecule is a double-stranded molecule that contains the bases A, T, G, and C in a certain order. As a result, we can define a gene as a certain base sequence or chargaff rule ratio formula.

Genes and Codons

  • Codons are three-nucleotide sub-segments that can be found in each gene. As a result, we can define a codon as a three-nucleotide-long or three-nucleotide-long segment or piece of DNA Strand. A gene is made up of a series of codons.
  • Because there are four nucleotides in DNA, the four nucleotides can be organised in 64 different ways. DNA’s instructions or genetic code are determined by the order or sequence of nucleotides. Apart from that, DNA strands or molecules are extremely lengthy. Without the proper packing, they will not fit within the cells. As a result, they create chromosomes by coiling firmly with histone proteins.

Further Readings

Reference