Okazaki Fragment
Definition
A short segment of DNA (100 to 200 nucleotides in eukaryotes) synthesised on the lagging template strand in the 5-prime to 3-prime direction away from the replication fork. Fragments are joined by DNA ligase after their RNA primers are replaced.
- Length in eukaryotes
- 100 to 200 nucleotides
- Strand synthesized
- Lagging template strand
- Synthesis direction
- 5' to 3', away from the replication fork
- Joined by
- DNA ligase, after RNA primer removal
Common questions
Why does lagging-strand synthesis need Okazaki fragments at all?+
DNA polymerase only extends in the 5' to 3' direction, so it cannot synthesize continuously toward the fork on that strand and instead builds short fragments backward that are later stitched together.
Why is this concept relevant to forensic DNA work rather than pure molecular biology?+
Understanding replication fidelity and repair around fragment junctions helps explain sources of mutation and degradation patterns that forensic scientists account for when interpreting DNA profiles from aged or damaged samples.
Related terms
- DNA Polymerase
- The enzyme that synthesises new DNA by adding deoxyribonucleoside triphosphates complementary to the template strand. In humans, polymerase delta copies the lagging...
- Frameshift Mutation
- A change in the reading frame of a coding sequence caused by an insertion or deletion of a number of nucleotides that...
- Point Mutation
- A change in a single nucleotide in the DNA sequence. A transition substitutes one purine for another or one pyrimidine for another...
- Semi-Conservative Replication
- The mode of DNA copying in which each daughter double helix retains one parental strand and acquires one newly synthesised strand, confirmed...
- Short Tandem Repeat (STR) Slippage
- Replication slippage at a repetitive locus where the template and nascent strands temporarily misalign. If the nascent strand slips forward, one repeat...