Molecular genetics Flashcards
Ankush Prashar (27 cards)
name 5 examples of modifying enzymes
methyltransferases, nucleases (DNases, RNases), DNA ligases, Polymerases (DNA/RNA polymerases), reverse transcriptases
what function do restriction endonucleases have?
cleave double stranded DNA at palindromic recognition sequences (e.g. GGATCC <-> CCTAGG) aka restriction sites
what are sticky ends?
complementary overhangs created by cleaving from restriction enzymes
- any two DNA molecules can form hydrogen bonds when they have complementary sticky ends
what is the difference between blunt and sticky ends?
blunt ends have an equal split (eg GT-AC/CA-TG)
sticky ends have and uneven split (eg G-AATTC/CTTAA-G)
what is the function of methyltransferases?
- catalysing the transfer of a methyl group to DNA bases
- used to block restriction sites
- also involved in epigenetics
what are deoxyribonucleases? name two types
nucleases that cleave single or double stranded DNA
- endonucleases: cut inside sequences
- exonucleases: cut from extremities
what are ribonucleases?
nucleases that cut RNA
what is the function of DNA ligases?
catalyse the formation of a covalent phospho-di-ester bond between the 5’ phosphate of one DNA fragment and the 3’ hydroxyl of another
name two types of DNA ligases
ATP-dependent DNA ligases
NAD-dependent DNA ligases
what is the function of DNA polymerase?
copy a DNA strand into another DNA strand
what is the “processivity” of DNA polymerase?
number of nucleotides added to the new strand per second
what is the “fidelity” of DNA polymerase?
rate of incorrect nucleases added -> errors
what is the function of RNA polymerase?
transcription of single stranded DNA into RNA
what are reverse trnscriptases?
RNA-dependent DNA polymerases
what is the function oof reverse transcriptases?
to transcribe single-stranded RNA into single stranded complimentary DNA (cDNA)
how are reverse transcriptases used in a lab?
to produce in vitro cDNA from RNA
what is a vector?
- small DNA molecule with regulatory and coding sequences
- foreign DNA can be inserted into the,
-> used as carriers of foreign DNA into host cells
what are the genetic markers of vectors?
selection of cells which have taken up the plasmid DNA
what is the multiple cloning site of a vector?
the site where DNA is inserted
what is the “origin of replication” of a vector?
replication of a vector tg w the foreign DNA fragment
what are plasmids (in molecular vector context)?
double stranded circular bacterial DNA used for molecular cloning to amplify or express the insert DNA into bacterial hosts
what are phagemids/phasemids?
- DNA cloning vectors derived from phage DNA and containing an origin of replication
- used to amplify insert DNA via bacteriophage replication into host cells
what are cosmids?
minimal phage vectors lacking the origin of replication
what are BACs?
bacterial artificial chromosomes
- large DNA vectors engineered from F plasmid
-> behaves like a chromosome
- used to carry large insert DNA up to 300Kb and create n store genomic libraries
-> useful in genome studies
