SAC 1? - enzymes that manipulate DNA Flashcards
(9 cards)
1
Q
role of restriction endonuclease in cutting DNA
A
- enzymes that cut DNA at particular DNA sequences called recognition sites.
- cleave the phosphodiester bond of the sugar-phosphate backbone holding DNA together
2
Q
what are recognition sites
A
- specific DNA sequences
- cut by the endonuclease, breaking the phosphodiester backbone on each strand
2
Q
sticky or blunt ends
A
- endonucleases leave fragments with overhanging/unbonded ends that have EXPOSED bases = STICKY
- Endonucleases that cut DNA in the middle of the recognition site to leave flat-ended fragments, with no overhanging nucleotides = BLUNT ENDS
2
Q
where are restriction endonuclease obtained
A
in BACTERIA
2
Q
function of RNA polymerase
A
- acts to build/assemble RNA molecules (copies DNA into RNA in TRANSCRIPTION)
- synthesises mRNA, rRNA and tRNA
- copies DNA template into mRNA
- no primer needed
- Builds a mRNA strand in a 5′ to 3’ direction (antiparallel to DNA template strand)
- adds RNA nucleotides until ‘stop’ sequence
- works slower than DNA polymerase
2
Q
function of DNA polymerase
A
- acts to REPLICATE/amplify DNA molecules (copies DNA into DNA in DNA replication)
- requires a primer to be made and attached to the template strand.
- makes double-stranded DNAs
2
Q
function of reverse transcriptase
A
- DNA polymerase that synthesises single-stranded DNA using single-stranded mRNA as a template
- REVERSE of usual transcription process (DNA -> RNA)
- makes DNA copy from RNA template
-> this DNA is called cDNA (complementary)
3
Q
function of Taq polymerase
A
- heat resistant DNA polymerase used in PCR
- comes from bacteria able to survive in high temperatures
- DOES NOT DENATURE
4
Q
function of DNA ligase
A
- permanently joins DNA fragments during LIGATION
- seals sugar-phosphate backbone
- forms phosphodiester bond between 2 fragments
- reverse of endonucleases
- (DNA ligase joins DNA fragments and RNA ligase joins RNA fragments)
