DNA replication process (Vietnamese explanation)

DNA Replication Process
📌 DNA is a double-stranded molecule composed of template and complementary strands running in opposite directions ($3'\rightarrow 5'$ and $5'\rightarrow 3'$ respectively).
🔗 The strands are held together by hydrogen bonds: Adenine (A) pairs with Thymine (T) via 2 H-bonds, and Guanine (G) pairs with Cytosine (C) via 3 H-bonds.
🧬 Replication follows three main steps: unwinding, synthesis of new strands, and formation of two daughter DNA molecules.

Step 1: Unwinding (Tháo xoắn)
🌀 The unwinding process is facilitated by the helicase enzyme, which separates the double helix into two single strands, resulting in a structure resembling a 'Y' shape.

Step 2: Synthesis of New DNA Strands (Tổng hợp mạch mới)
⛓️ The enzyme DNA polymerase synthesizes new strands strictly in the $5'\rightarrow 3'$ direction.
🏃 On the template strand oriented $3'\rightarrow 5'$, synthesis is continuous from right to left (following the unwinding progression).
🐢 On the complementary template strand oriented $5'\rightarrow 3'$, synthesis must occur in short segments, known as Okazaki fragments, as it proceeds from left to right, waiting for the DNA to unwind.
🔗 After synthesis, the enzyme ligase joins these short Okazaki fragments together to form a complete polynucleotide chain.

Step 3: Formation of Daughter DNA Molecules
✨ One round of DNA replication results in two identical daughter DNA molecules from the single parent molecule.
🔄 Each new DNA molecule consists of one old template strand and one newly synthesized strand, illustrating the semi-conservative principle (bán bảo tồn).

Key Points & Insights
➡️ The initial unwinding of the DNA double helix is performed by the helicase enzyme.
➡️ Synthesis on the $3'\rightarrow 5'$ template strand is continuous, while synthesis on the $5'\rightarrow 3'$ template strand occurs discontinuously via Okazaki fragments.
➡️ The fundamental principle of DNA replication is semi-conservative, meaning each new DNA molecule retains one original strand and one new strand.

📸 Video summarized with SummaryTube.com on Jan 22, 2026, 07:10 UTC