Molecular Basis of Inheritance – Notes
Structure of DNA
Nucleic acids are made up of polynucleotide chains, which are formed by several nucleotides that make up the structure of the DNA when bonded together.
The length of DNA is defined by the number of nucleotides or pairs of nucleotides present in the DNA.
It was Friedrich Meischer who first identified the DNA as an acidic material present in the nucleus in 1869.
In 1953, James Watson and Francis Crick proposed the revolutionary simple double helix model for the structure of DNA.
Packaging of DNA Helix
In prokaryotes, the negatively charged DNA is arranged in large loops and is held together by a few positively-charged proteins in a region known as the nucleotide.
Eukaryotes contain a single molecule of negatively charged DNA packaged around a spool of positively charged, basic proteins known as histones.
Histones are arranged to form a unit of eight molecules known as the histone ocatmer.
Around the positively charged ocatmer, a negatively charged DNA molecule is wrapped to form a structure known as the nucleosome, which is held in place by the H1 histone.