What are 5' and 3' in DNA and RNA strands? Please clarify with some images and please use simple English.
The 5' and 3' mean "five prime" and "three prime", which indicate the carbon numbers in the DNA's sugar backbone. The 5' carbon has a phosphate group attached to it and the 3' carbon a hydroxyl (-OH) group. This asymmetry gives a DNA strand a "direction". For example, DNA polymerase works in a 5' -> 3' direction, that is, it adds nucleotides to the 3' end of the molecule (the -OH group is not shown in diagram), thus advancing to that direction (downwards).
The no 5 and 3 are the carbon no of the carbon skeleton ring of deoxyribose as similar as any other organic compound. In any nucleic acid, RNA or DNA 3' refers to the 3rd carbon of sugar ribose or deoxyribose which is linked to OH group and 5' linked to a triple phosphate group. So these 5' and 3' group provide a directional polarity to the DNA or RNA molecule. Now a good question would be y 3' and 5' not 3 and 5. It is simply to differentiate sugar carbons from that of the bases which are also having a carbon skeleton and thus nos for their carbon
protected by Chris♦ Oct 27 '14 at 18:10
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