enzymes that manipulate DNA

types of enzymes that manipulate DNA (3)

recognition enzymes

ligase

polymerase

what is a restriction enzyme

An enzyme that cuts DNA at a specific sequence of nucleotides

where does a restriction enzyme cut

at the recognition site

what does a restriction enzyme cut

sugar-phosphate back bone

property of recognition sites

palindromic (same both ways on each strand)

why do prokaryotes have restriction enzymes

they don't have an immune system so the endonucleases prevent injected viral DNA from hijacking the system by cutting it

other name for restriction enzymes

endonuclease

types of cuts made by a restriction enzyme (2)

sticky

blunt

sticky end

cuts double strand at different spots, leaving one side overhanging (longer than the other)

property of sticky end

is specific - can only be joined to other segments cut by the same endonuclease

blunt end

cuts double strand straight down, leaving a flat end to the DNA fragment

property of a blunt end

non specific - can be joined to any other blunt end

what is a ligase

an enzyme that joins fragments of DNA / RNA together

how does a ligase work

reforms the phosphodiester bonds (covalent) in the DNA bonding

what is ligation

the process of joining two or more segments of DNA together

what happens in ligation

two pieces of DNA are cut using the same restriction enzyme

two different DNA fragments are attached to each other by weak hydrogen bonds

ligase reforms phosphodiester bonds

what is recombinant DNA

any DNA made from multiple sources

what is annealing

when two matching 'sticky ends' come together, they join by complementary base pairing

* attached from base pairing only

when does annealing occur

before ligation

what is a polymerase

a type of enzyme that amplifies / multiplies sections of DNA / RNA

DNA synthesis

making DNA strands from DNA

RNA synthesis

making RNA strands from DNA

reverse transcriptase

making complementary DNA from a mRNA strand

types of polymerase (4)

DNA polymerase

taq polmerase

RNA polymerase

reverse transcriptase

what is reverse transcriptase

type of enzyme that can generate a DNA strand from an RNA template, it is commonly used to isolate genes after te introns have been spliced

which way does the restriction enzyme read

5'-3'

what is the function of the restriction enzyme in the bacteria

acts as an immune defence mechanism against bacteriophages by allowing the bacteria to digest the nucleic acid

what does DNA polymerase catalyse

condensation polymerisation

what direction does the DNA polymerase build the complementary strand

5' - 3'

what is DNA polymerase not able to do

cannot unwind the DNA molecules double helix to expose the template strands