Question

Chains of nucleic acids have directionality and are read in a certain way just like languages are read from "left to right" or "right to left."

DNA is always read in the_______direction, 3' to 5' or 5' to 3'
whereas RNA is read in the_______direction, 3' to 5' or 5' to 3'

Answer 1

Ans.

During DNA replication, DNA polymerase synthesizes new daughter strand in 5' to 3' direction as it can add new nucleotide molecules at 3'-OH group of growing strand only. During transcription, RNA polymerase also synthesizes RNA molecules in 5' to 3' direction. Thus, the template DNA is always read by DNA polymerase or RNA polymerase in 3' to 5' direction.

During translation, a long polypeptide chain is made by reading information from mRNA molecule. The RNA molecule during protein synthesis is always read in 5' to 3' direction, from start codon to stop codon.

Thus, the correct answer to fill in first blank is 3' to 5' and in second blank is 5' to 3'.

Answer 2

When DNA is replicated it is read by the DNA polymerase in the 3’ to 5’ direction, but it is built in the 5’ to 3’ direction.

When mRNA is made from DNA, the RNA polymerase reads the DNA in the 3’ to 5’ direction. But it too is built in the 5’ to 3’ direction.

The mRNA is read by the ribosome in the 5’ to 3’ direction.

So I would answer:
DNA 3’-5’
RNA 5’-3’