While DNA is the “blueprint of life,” RNA performs the actual work of building the proteins that make up living things.
RNA stands for ribonucleic acid, the nucleic acid partly consisting of the sugar ribose. This sugar is one of the ways in which RNA differs from DNA, which contains deoxyribose instead. RNA has three of the same nitrogen-ring bases as DNA and one that is different, called uracil, in place of thymine. DNA is double stranded. RNA is usually thought of as being as being single stranded, although some kinds of RNA are partially double stranded or looped into different shapes. These differences between the two help to protect DNA from degrading or mutating, because DNA needs to last for a long time. Most kinds of RNA are used quickly and degrade rapidly.
Different kinds of RNA play different roles in the synthesis of proteins. Messenger RNA (mRNA) is formed using DNA in the cell’s chromosomes as a template, duplicating the DNA’s information in a process called transcription. It carries the information out of the cell’s nucleus into the endoplasmic reticulum, where proteins are made. The mRNA binds to bodies there called ribosomes, which are partly composed of another type of RNA, ribosomal RNA (rRNA). Transfer RNAs (tRNAs) are short pieces of RNA found in the fluid of the endoplasmic reticulum. These carry individual amino acids, the building blocks of protein. The tRNAs line up so that their own bases bond to complementary ones along the base sequence of the mRNA, placing the amino acids in the correct order before they are bonded together. This process of synthesizing protein along a strand of mRNA is called translation.
There are other kinds of RNA that are not directly involved in protein synthesis. Some of them help to regulate genes, turning them on or off or slowing them down so that they make less mRNA. Some have the job of modifying other strands of RNA or of protecting DNA from being altered. RNA’s ability to shut down or slow down genes is the basis for cutting edge research in the field of RNA interference (RNAi), which could someday lead to therapies for viral or genetic diseases.
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