What is DNA and how is it formed? 

The fundamental building block of chromosomes is deoxyribonucleic acid (DNA).

DNA is a double-stranded molecule that forms a helical structure, resembling a twisted ladder or double helix.

Composition of DNA

DNA is composed of four types of nucleotides, and each nucleotide consists of a sugar molecule, a phosphate group, and a nitrogenous base. The four nitrogenous bases are 

• Adenine (A)

• Thymine (T)

• Cytosine (C)

• Guanine (G). 

The arrangement of these bases along the DNA strand constitutes the genetic code, serving as instructions for the synthesis of proteins and the transmission of genetic information.

Nucleotides

Nucleotides are like tiny Lego pieces of our genetic code. They have a sugar, a phosphate, and a special letter (A, T, C, or G), and when they link together, they create instructions for building and maintaining living things.

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Histones

DNA is tightly wound around proteins called histones, forming structures known as nucleosomes.

Histones help in organising and compacting the long DNA strands, facilitating the packaging of genetic material within the cell nucleus.

Structure of DNA

• Double Helix: 

The DNA molecule consists of two long strands that coil around each other to form a double helix. The sides of the ladder are made up of alternating sugar (deoxyribose) and phosphate molecules.

• Base Pairs: 

The rungs of the ladder are made up of pairs of nitrogenous bases. There are four types of bases: adenine (A), thymine (T), cytosine (C), and guanine (G). Adenine pairs with thymine, and cytosine pairs with guanine, forming complementary base pairs.