Which of the following base is usually not present in DNA?
Uracil is not usually present in DNA, instead thymine is present. However in DNA, spontaneous deamination of cytosine can produce uracil. But, this uracil is promptly recognized by Uracil DNA-glycosylase and replaced with cytosine. If uracil were present in DNA, DNA machinery could not differentiate the original uracil and the deaminated cytosine. Thus, presence of thymine/absence of uracil gives stability to DNA. Uracil is present in RNA in place of Thymine in DNA
Adenine
Guanine
Cytosine
Uracil
Basics of DNA