nitrogenous base found in DNA but not in RNA
The nitrogenous base found in DNA but not in RNA is called thymine (T). To understand why thymine is present in DNA but not in RNA, we need to know the key differences between these two types of nucleic acids.
Both DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are made up of nucleotides, which are the basic building blocks of these molecules. A nucleotide consists of three components: a nitrogenous base, a sugar molecule, and a phosphate group.
In DNA, the nitrogenous bases are adenine (A), cytosine (C), guanine (G), and thymine (T). RNA, on the other hand, uses adenine (A), cytosine (C), guanine (G), but instead of thymine (T), it contains uracil (U).
The reason for this difference lies in the function of these nucleic acids. DNA stores genetic information and is primarily located in the cell nucleus. Thymine is structurally more stable than uracil and provides better protection to the genetic information. Therefore, thymine is used in DNA as a way to ensure stability of the genetic code.
On the other hand, RNA is involved in various processes within the cell such as protein synthesis. Uracil is structurally similar to thymine but lacks a methyl group, making it less stable. This instability is acceptable because RNA is a more transient molecule, constantly being synthesized and degraded as needed.
To summarize, the nitrogenous base thymine is found in DNA but not in RNA, as it provides greater stability to the genetic information stored in DNA. RNA, being more involved in dynamic cellular processes, uses uracil instead of thymine.