biology / Genetics & Information / free

DNA Replication

Unzip a strand and follow the rules that copy its information.

Follow the mechanism1 / 3

A template strand is exposed. Opening a local fork reveals bases whose sequence carries the information for a new strand.

replication forkcomplementary pairing

Focus the idea

copied2 / 5

next pairG–C

ruleA–T / G–C

checkmatched

Move replication fork 2 / 5

The fork has copied 2 of 5 positions. The next template base G constrains the new base to C, added to the growing 3' end.

Each original strand acts as a template. DNA polymerase adds nucleotides only to a 3' end, so synthesis runs 5'→3': the leading strand grows continuously toward the fork, while the lagging strand is made in short Okazaki fragments away from it and joined by ligase. Proofreading catches some copying errors instead of assuming every first pass is perfect. Five bases stand in for a whole chromosome.

Guided journey

Walk through the process.

Step 1 of 4: 01 / Open a local fork

The double helix separates in a small region, exposing two template strands.

What changes next: The sequence can be read without unzipping the entire molecule.

04 / PRACTICE

Make the biology yours.

0 / 3 checked

Answer from the model, then use the explanation to connect the visual mechanism to the biological rule.

CHECK 1 / 3