25-08-2017, 09:32 PM
Genomic library and cDNA library
library $ molecular probe.ppt (Size: 3.87 MB / Downloads: 65)
What is a DNA Library
Genomic Library: Bank of DNA that represents the genome of
specific cell/organism/species
cDNA Library: Bank of cDNA representing mRNA of a specific cell.
Originally libraries made in vectors- allow replication in E.Coli
Later, linker libraries for PCR based cloning-
”Marathon Libraries”
Genomic Library:
ways to make a genomic library:
Complete digestion (at all relevant restriction sites)
Produces a large number of short DNA clones.
Genes containing two or more restriction sites may be cloned in two or more pieces.
Mechanical shearing
Produces longer DNA fragments.
Ends are not uniform, requires enzymatic modification before fragments can be inserted into a cloning vector.
Partial digestion
cDNA Library:
cDNA is derived from mature mRNA, does not include introns.
cDNA may contain less information than the coding region.
cDNA library reflects gene activity of a cell at the time mRNAs are isolated (varies from tissue to tissue and with time).
mRNA degrades quickly after cell death, and typically requires immediate isolation (cryoprotectants can increase yield if immediate freezing is postponed by field work).
Creating a cDNA library:
Isolate mRNA
Synthesize cDNA
Clone cDNA