DNA replication and recombination

• For transmission to occur, genetic material must be copied. 
• During this process, DNA replication, orignal DNA strands are used as templates for syntheis of new DNA strands

Structural overview of DNA replication 

• DNA is a double heloix composed of two DNA strands 

Existing DNA strands Act as Templates for synthesis of new strands 

• Durig the replication process, two complementary strands of DNA come apart and serve as a template strands, or parental strands for synthesis of two new strands of DNA. 

Bacterial chromosomes contain a single origin of replication 

• A replication fork is the site where the parental DNA strand have seperated and new daugher strands are being made. 

Replication is initiated at the origin of replication 

• Considerable research has focused on the origin of replication oin E.coli. The origin is named for origin of Chromosome replication. 

Synthesis of RNA primers bia primase 

• Leading strand, made in the same direction as the replication fork is moving in, a single primer is made at the origin of replication. 
• Lagging strand, made in short fragmebts in the opposite direction from the movement of the replication fork; multiple primer are made

Synthesis of DNA 

• An enzyme known as DNA polymerase is responsible for synthesing the DNA of the leading and lagging strands. 
• Enzyme catalyze the formation of covelent bonds between adjacent nucleotides, thereby making the new daughter strands. 

Syntehsis of the leading and lagging strands is diffrent 

• DNA polymaerase can attach nucleotides only in the 5 to 3 directions, not in the 3 to 5 direction.

Certain enzymes of DNA replication bind to each other to form a complex

• DNA helicase and primase are physically bound to each other to form a complex known as a primosome.

DNA polymerase is a processive enzyme that uses deoxyribonucleoside triphosphates 

• Nucleotide about to be attached to the growing strand is a dNTP containing three phosphate groups attached at at the 5 -carbon atom of deoxyribose. 
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