មូលដ្ឋានជីវវិទ្យានៃ DNA

Replication

• Process: DNA replication occurs in three stages: initiation, elongation, and termination.
• Initiation: The process begins with the unwinding of the double helix at a specific region called the origin of replication.
• Elongation: An enzyme called helicase unwinds the DNA, and another enzyme called primase adds short RNA primers to the template strands.
• Termination: The process is completed when the replication forks meet, and the new DNA molecules are formed.
• Semi-conservative: DNA replication is semi-conservative, meaning that each new DNA molecule contains one old strand (template) and one new strand synthesized during replication.

Structure

• Double Helix: DNA is a double-stranded molecule shaped like a double helix, where two complementary strands are twisted together.
• Nucleotides: DNA is composed of nucleotides, which are the building blocks of DNA. Each nucleotide consists of a sugar molecule, a phosphate group, and one of four nitrogenous bases: adenine (A), guanine (G), cytosine (C), and thymine (T).
• Base Pairing: The nitrogenous bases pair in a specific manner: A-T and G-C.
• Hydrogen Bonding: The base pairs are held together by hydrogen bonds, which are weak chemical bonds between the nitrogenous bases.

Transcription

• Process: Transcription is the process of creating a complementary RNA copy from a DNA template.
• Initiation: Transcription begins with the binding of an enzyme called RNA polymerase to the DNA template.
• Elongation: RNA polymerase reads the DNA template and matches the incoming nucleotides to the base pairing rules (A-T and G-C).
• Termination: Transcription is completed when the RNA polymerase reaches the termination sequence, and the RNA transcript is released.
• Types of RNA: There are three main types of RNA produced during transcription: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA).