Enzymes that manipulate DNA Flashcards
what are the enzymes that manipulate DNA
endonucleases, ligases and polymerases
what do endonucleases do
they cut DNA, the sugar phosphate bonds between nucleotides
how do endonucleases work
they target a specific recognition site, which is usualy a six base paladromic sequence, once it encounters this sequence it will bond to the dna sequence and cut into each of the two sygar-phosphate backbones of the douuble helix to create blunt or sticky ends
where are endonucleases found
bacteria, bacteria use them as a defence against bacteriophages
how does a bacterias dna not get cut
they dont have the same dna or recognition sooites and the virus’/bacteriophages
what does palandromic mean
a sequence of doble stranded dna that reads the same base sequence for both strands in a 5-3 direction
where can blunt ends be cut
only in the centre of the 6 base sequence
what do ligases do
enzymes that join fragments of dna or rna (dna ligase and rna ligase
how ligases work
they seal and form the stong covalent, phosphodiester bonds between the okzaki fragments
what do polymerases do
synthesise polymer chains from monomer building blocks
what are the two types of polymerases and what are they used for
rna polymerase - used primarily in transcription, dna polymerase 5-3 - used in the amplification and replication of dna 5-3
what is required for polymerase to finish amplifying dna
ligases and there are no sugar phosphate bonds between the fraggments, ligases must do this
what do polymerases require to start
primers attached to the start of a template starnd (short sequences of nucleotides complementary to the template strand.
