Okazaki fragments are short pieces of DNA made on the lagging strand during DNA replication, because DNA can only be built in one direction. They are later joined together by DNA ligase to form a continuous strand.

Class 10 version

  • DNA replication happens on two strands.
  • One strand is made continuously, called the leading strand.
  • The other strand is made in small chunks, called Okazaki fragments.
  • These chunks are then linked together by DNA ligase.

Why they form

DNA polymerase can add new DNA only in the 5' to 3' direction. Because of this, the lagging strand cannot be copied smoothly, so it is copied piece by piece.

Easy line to remember

Okazaki fragments = small DNA pieces on the lagging strand.

Exam answer

Okazaki fragments are short DNA segments formed discontinuously on the lagging strand during DNA replication and joined by DNA ligase.