Question

What is the basis for the difference in the synthesis of the leading and lagging strand of DNA molecules?

• A. Origins of replication occur only at the 5' end of the molecule
• B. DNA ligase works only in the $3^{\prime }\to 5^{\prime }$ direction
• C. DNA polymerase can add new nucleotides only to the 3' end of the growing strand
• D. Helicases and single-strand binding proteins work at the 5' end

Answer 1

Answer: (C)

DNA polymerase can add new nucleotides only to the 3' end of the growing strand

The new DNA strand that grows continuously in the 5' to 3' direction is called the leading strand. The basis of the difference between the leading and lagging strand is that DNA polymerase can join new nucleotides only to the 3' end of the growing strand. Okazaki fragments are formed on the lagging strand and they are joined by the activity of DNA ligase.

So, the correct option is 'DNA polymerase can join new nucleotides only to the 3' end of the growing strand'.