1 What is meant by the sentence Nucleic acids have polarity

1. What is meant by the sentence: “Nucleic acids have ‘polarity’”? Explain the difference between the 5’ and 3’ ends of a single-stranded nucleic acid and describe the ‘antiparallel’ nature of double-stranded DNA.

Solution

The back bone of nucleic acid is connected with sugar and phosphate arranged as a chain by phosphodiester bonds. One end carries the sugar and it is the 5\' end and the other end carries phosphate and it is 3\' end. DNA has two complementary strands, one is in 5\' to 3\' direction and other is in 3\' to 5\' direction. The 5\' end has a hydroxyl group and 3\' has a phosphate group. Nucleic acids are synthesised from 5\' to 3\' direction. A new nucleotide is added to the 3\' phosphate group by the polmerase enzyme.

DNA has double strand s of nucleotides. One strand is in 5\' to 3\' direction( serve as template strand) and other one is in 3\' to 5\' direction. so it is in opposite direction and is complimentary to each other. So they are antiparellel to each other.