1. S E R I A L A N A L Y S I S O F
G E N E E X P R E S S I O N
( S A G E )
PRESENTED BY:
A SHWINI.R
B.SC+M.SC -BIOTECH
A MITY INSTITUTE OF
BIOTECHNOLOGY
2. Serial Analysis of Gene Expression (SAGE)
• Serial analysis of gene expression (SAGE) is an approach that allows
rapid and detailed analysis of overall gene expression patterns.
• SAGE method allows for a quantitative and simultaneous analysis of
a large number transcripts in any particular cells or tissues, without
prior knowledge of the genes.
• This method takes advantage of the 3’-portion of mRNA as the gene
tag, but of much shorter form (9–10 bp).These tags can be serially
connected before cloning into a plasmid vector.
• Since the resulting plasmid clones contain multiple tags, sequences
of several dozens of mRNAs can be obtained by a single sequencing
reaction.
3. • A short sequence tag (10-14bp) contains sufficient
information to uniquely identify a transcript provided
that that the tag is obtained from a unique position
within each transcript;
• Sequence tags can be linked together to from long serial
molecules that can be cloned and sequenced; and
• Quantitation of the number of times a particular tag is
observed provides the expression level of the
corresponding transcript.
• Linking the tags together allows for rapid sequencing
analysis of multiple transcripts.
• By linking the tags together, only one sequencing event is
required to sequence every transcript within the cell.
• Makes the task of DNA expression profiling a much
easier
SAGE Principle
9. Advantages:
• mRNA sequence does not need to be known
prior, so genes of variants which are not known
can be discovered.
• Its more accurate as it involves direct counting
of the number of transcripts.
Disadvantages:
• Length of gene tag is extremely short (13 or 14bp),
so if the tag is derived from an unknown gene, it is
difficult to analyze with such a short sequence.
• Type II restriction enzyme does not yield same
length fragments.
• mRNA levels and protein expression do not are
always correlate.