Why is Thymine Present in DNA?

1. Thymine has a high resistance to photochemical mutation.
2. It makes genetic code more durable. 
3. It has great resistance.

Due to the high resistance of thymine, it is present in the DNA because DNA is transferred from generation to generation any  mismatching leads to mutation which nigh be lethal

DNA is a micromolecule that consists of many subunits it’s connected together. Those subunits knew as nucleotides. The DNA provides replication and information storage. DNA is described as deoxyribonucleic acid generally it is a polymer of deoxyribonucleotides it’s found in chromosomes, mitochondria chloroplast. It has a double-stranded structure and it acts as genetic material in most organisms they carry the genetic information from one generation to another generation. In 1953, James Watson and Francis crick described as DNA a double helix structure.