Glossary
mRNA: Messenger RNA that carries genetic code from
genes and dictates protein production. It is an expressed form of a gene.
cDNA: Complementary DNA (cDNA) that is copied from
mRNA. The genetic code on a cDNA molecule is equivalent to that of a gene.
cDNA library: a collection of cDNAs that are cloned from a specific
tissue and maintained on a set of bacterial cloning vectors.
EST: Expressed Sequence Tag, a short fragment
(usually 200 to 500 nucleotides long) of a gene that can be used to help
identify unknown genes. ESTs are generated by sequencing either one or both
ends of cDNAs. The idea is to sequence bits of expressed genes and then use
these "tags" to paste a complete gene together based on overlapping
sequences. ESTs also provide information on the number and type of genes
turned on in a specific tissue of an organism.
DNA microarray: Thousands of bits of DNAs printed on a glass slide
for screening genes that are switched on and off in response to internal and
external factors, such as regulatory proteins, pathogens and stresses.
Gene expression profile: A gene can exert its function only after it
is transcribed from DNA to mRNA and then translated from mRNA to protein.
Gene expression profile is an inventory of expressed genes in mRNA form
(referred to as transcriptome) and in protein form (proteome). The objective
of the gene expression profiling is to identify the mode of action of genes.
