A DNA sequence made from a messenger RNA molecule, using an enzyme called reverse transcriptase. Conservation Genes that are present in two distinct organisms are said to be conserved. The more similarities there are, the more highly conserved the two sequences. Eukaryote An organism whose cells have a complex internal structure, including a nucleus. Animals, plants and fungi are all eukaryotes.
ESTs have been used to hunt for genes, so hundreds of thousands are present in sequence databases.
The complete DNA sequence of an organism. Heterochromatin Compact, gene-poor regions of a genome, which are enriched in simple sequence repeats. As it can be impossible to clone , heterochromatin is often ignored when calculating the percentage of a genome that has been sequenced. Introns and exons Genes are transcribed as continuous sequences, but only some segments of the resulting messenger RNA molecules contain information that codes for the gene's protein product. These segments are called exons.