Bio D1.1 - DNA Replication

DNA replication

production of new DNA with base sequences identical to existing strands, used for reproduction and growth/tissue replacement

Semi-conservative process

One strand is original, the other is synthesized

mRNA

a temporary copy of genes

replication fork

site where a parent DNA molecule is separated into 2 single strands by breaking the hydrogen bonds

helicase

unwinds double helix and separates 2 strands by breaking hydrogen bonds

primase

creates short RNA primers and provides a 3’ OH group for bonding to nucleotides

DNA Polymerase III

adds nucleotides from the 5’ to 3’ direction in a complementary pattern

DNA Polymerase I

removes RNA primers and replaces with DNA nucleotides in 5’ to 3’ direction

Leading strand

runs from 5’ to 3’ towards replication fork, continuously synthesized

lagging strand

runs 3’ to 5’ towards replication fork, synthesized in sections

okazaki fragments

sections of DNA formed during discontinuous synthesis on the lagging strand

Ligase

forms phosphodiester bonds between DNA nucleotides and joins okazaki fragments

polymerase chain reaction

used for copying DNA artificially, occurs in a thermocycler

Stage 1 in PCR

denaturation at ~90 degrees C, DNA unwinds into single strands

Stage 2 in PCR

Annealing at ~55 degrees C, allowing primers to bind to DNA sample to designate desired sequence

Stage 3 in PCR

Elongation at ~75 degrees C, Taq DNA polymerase replicates both strands starting at the primer, produces 2 copies of DNA

Gel electrophoresis

used to separate and isolate DNA based on mass and size

Process of gel electrophoresis

sample is placed in gel & electric current is applied causing DNA to move through gel