EST (Expressed Sequence Tag)

The EST database contains sequence records from the bulk EST (Expressed Sequence Tag) division of GenBank. These are typically short single-pass reads from cDNA libraries often generated as large survey project. Data from EST can be used to catalog expressed genes for a particular organ, tissue or cell type or general for a species, and compare expression levels of genes in various library sources

UCSC Genes Track

The UCSC Genes track is a set of gene predictions based on data from RefSeq, Genbank, CCDS, UniProt, Rfam, and the tRNA Genes track. The track includes both protein-coding genes and non-coding RNA genes. Both types of genes can produce non-coding transcripts, but non-coding RNA genes do not produce protein-coding transcripts. This is a moderately conservative set of predictions. Transcripts of protein-coding genes require the support of one RefSeq RNA, or one GenBank RNA sequence plus at least one additional line of evidence. Transcripts of non-coding RNA genes require the support of one Rfam or tRNA prediction. Compared to RefSeq, this gene set has generally about 10% more protein-coding genes, approximately four times as many putative non-coding genes, and about twice as many splice variants.

Expressed Sequence Tags

Expressed Sequence Tags (ESTs)

ESTs are short (200–500 nucleotides) DNA sequences that can be used to identify a gene that is being expressed in a cell at a particular time.The Procedure:

• Isolate the messenger RNA (mRNA) from a particular tissue (e.g., liver)
• Treat it with reverse transcriptase. Reverse transcriptase is a DNA polymerase that uses RNA as its template. Thus it is able to make genetic information flow in the reverse (RNA ->DNA) of its normal direction (DNA -> RNA).
• This produces complementary DNA (cDNA). Note that cDNA differs from the normal gene in lacking the intron sequences.
• Sequence 200–500 nucleotides at both the 5′ and 3′ ends of each cDNA.
• Examine the database of the organism's genome to find a matching sequence.
• That is the gene that was expressed.