DNA replication, RNA transcription and translation

	Initiation	Elongation	Termination
DNA Replication	DNA Helicase unwinds the double helix by breaking the hydrogen bonds holding together the complementary nitrogenous base pairs. Single-stranded binding proteins bond with the base pairs to prevent the bonding of hydrogen. Gyrase relieves the tension by cutting the DNA strand into shorter strands. Primase signals the synthesis of RNA primers in order to initiate the elongation.	DNA Polymerase III elongates the new strand in the 5’ to 3’ direction, and uses the 3’ to 5’ direction of the template strand. Leading strand synthesizes continuously towards the replication fork.  Lagging strand synthesizes discontinuously away from the fork in segments called Okazaki fragments	DNA Polymerase 1 proofreads the newly formed strand and replaces the RNA primers with the appropriate nucleotides. DNA DNA Ligase glues the Okazaki fragments by forming phosphodiester bonds.
RNA transcription	Similar to DNA, Helicase unwinds the double helix and RNA polymerase binds at the promoter region. The TATA box promotes  various transcription factors to come together to initiate elongation RNA transcription does not require a primer to initiate elongation.	Like DNA replication, mRNA is synthesized in the direction of 5’ to 3’ by RNA polymerase and uses 3’ to 5’ direction of the template strand. RNA sequence is complementary to this template strand, and is similar to that of the coding strand. Uracil replaces thymine in RNA sequences.	The terminator sequence – AAUAAA signals the end of transcription. The synthesized mRNA floats away from the DNA template and prepares to be further synthesized before leaving the nucleus.
RNA translation	Ribosome binds to the 5’cap of the mRNA.  tRNA transfers the correct amino acids to a ribosome. The anticodon carried by the tRNA matches with the complementary mRNA codon In triplets, tRNAs deposit amino acids in the prescribed order. Ribosome joins them into a polypeptide chain. The codon AUG is the start codon generally.	The initial amino acid, codon AUG enters the peptide site, with the next amino acid entering the accepter site. The first amino acid bonds with the second amino acid. As the ribosome shift over one codon, the third amino acid enters A site with the second codon in the P site attached to the first codon. This process repeats until a stop codon is detected.	The stop codons, UGA, UAG, UAA signal termination of protein synthesis. A protein known as a release factor helps relase the polypeptide chain from the ribosome.