DNA Replication DNA replication is the process by which a DNA molecule is copied to create two identical copies. This process is essential for maintaining t...
DNA Replication
DNA replication is the process by which a DNA molecule is copied to create two identical copies. This process is essential for maintaining the genetic integrity of an organism. DNA replication occurs in four steps: initiation, elongation, termination, and proofreading.
Initiation: DNA replication begins at specific regions called origins of replication. These origins are typically found near the ends of chromosomes, where the DNA is highly repetitive. RNA primers are used as templates to synthesize complementary DNA strands in the 5' to 3' direction.
Elongation: Once DNA replication has initiated, DNA polymerase enzymes extend the DNA strands in a 5' to 3' direction. DNA polymerase can add nucleotides to the growing DNA strand, matching the template strand. Complementary base pairs (A with T and C with G) are added to form a new DNA strand.
Termination: DNA replication is terminated when DNA polymerase reaches a stop codon, which is a specific sequence of nucleotides. DNA polymerase ceases to add nucleotides, and the DNA strands are cleaved apart, releasing the two newly formed DNA molecules.
Transcription
Transcription is the process by which an RNA molecule is synthesized from a DNA template. Transcription occurs in three steps: initiation, elongation, and termination.
Initiation: RNA polymerase binds to a specific region of DNA called the promoter, which is a region of DNA that is complementary to the mRNA template. The promoter is recognized by the polymerase as it forms a groove that allows the polymerase to access the DNA template.
Elongation: Once the RNA polymerase has bound to the promoter, it starts to synthesize an RNA molecule in the 5' to 3' direction. The RNA strand is complementary to the DNA template strand, except that thymine (T) is replaced by uracil (U) in RNA. The RNA polymerase adds nucleotides to the growing RNA strand, matching the DNA template strand.
Termination: Transcription is terminated when the RNA polymerase reaches a stop codon, which is a specific sequence of nucleotides. The RNA polymerase ceases to add nucleotides, and the DNA template is cleaved apart, releasing the mRNA molecule.
Translation
Translation is the process by which an mRNA molecule is used as a template to synthesize a protein. Translation occurs in three steps: initiation, elongation, and termination.
Initiation: tRNA molecules bring amino acids to the ribosome in the correct order, according to the mRNA sequence. A start codon on the mRNA is recognized by the ribosome, and the polypeptide chain begins to grow.
Elongation: Once the ribosome has started translating the mRNA, it moves along the mRNA in a 5' to 3' direction. Each codon on the mRNA corresponds to a specific amino acid, and the ribosome reads the mRNA sequence to assemble the amino acids in the correct order.
Termination: Translation is terminated when the ribosome reaches a stop codon, which is a specific sequence of nucleotides. The stop codon causes the ribosome to release the protein molecule and return to its initial position