I read in some place that tRNA has a part which is double-stranded. I wanted to know if that part is similar to DNA (double-helix). (And I know that tRNA won't contain Thymine)
closed as off-topic by anongoodnurse, AliceD♦, kmm, March Ho, James Jul 14 '16 at 5:58
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It is right that RNA has small areas of complementary base pairing. You asked whether these parts are double helical.
DNA has various types of double-helical conformations. Most popular among them is the B-form, A-form and Z-form. The Watson Crick model is similar to the B-form of DNA. It is right-handed double-helical structure. A-form and Z-form are different from this, e.g,. Z-form has left handed rotation and the number of base-pairs in each helical turn is 12; whereas in B-form it is 11. So, there isn't a single structure of DNA that you can specify by saying the term double helical.
t-RNA has multiple segments that are double stranded, separated by loops (called hairpin loops) and bulges. These molecules have a complex structure (are not symmetrical like the Watson-Crick model). This confirmation helps in its function. As a general rule, when two complementary base sequences (that may be DNA or RNA) come in close proximity, they tend to pair.
Nascent RNA molecule (single stranded) try to assume a right handed helical conformation, but note that it is very different from double-helix. When two strands of RNA, perfectly complementary to each other come in close vicinity they pair into a right handed double helix(A-form); however these molecules are very uncommon in nature.
Other examples of double strand formation in m-RNA are terminal signal of the transcription process in E. coli.
For further knowledge you may read
- Biochemistry by Stryer
- Lehninger principles of Biochemistry.