TERMS AND CONCEPTS

An EXCELLENT overview of DNA, RNA, genomes and general terms associated with biotechnology.

Check out the glossary of terms at the Maize Database.

More help with molecular genetics terms from NCBI.

1. Intron - Non-coding DNA that is transcribed and then is degenerated and removed from mRNA. A polynucleotide sequence in a nucleic acid that does not code information for protein synthesis and is removed before translation of messenger RNA 

2. Exon - Primary DNA code that leaves the nucleus as mRNA. A polynucleotide sequence in a nucleic acid that codes information for protein synthesis and that is copied and spliced together with other such sequences to form messenger RNA

3. cDNA - "complementary" DNA. DNA synthesized from an mRNA template. cDNA is single-stranded DNA made in the laboratory from a messenger RNA template under the aegis of the enzyme reverse transcriptase. This form of DNA is often used as a probe in the physical mapping of a chromosome.

4. EST - Expressed Sequence Tag (derived from cDNAs). A unique stretch of DNA within a coding region of a gene that is useful for identifying full-length genes and serves as a landmark for mapping. An EST is a STS derived from cDNA.

5. STS - Sequence Tagged Site. A short segment of DNA which occurs but once in the genome and whose location and base sequence are known. STSs are detectable by the polymerase chain reaction (PCR), are helpful in localizing and orienting mapping and sequence data, and serve as landmarks in the physical map of the genome.

6. GenBank - A database containing all known sequences of DNA strands, categorized by alphanumeric code. Click here for an overview of GenBank.

7. TUG - Tentative Unique Genes

8. ORF - Open Reading Frames. Reading frames where successive nucleotide triplets can be read as codons specifying amino acids and where the sequence of these triplets is not interrupted by stop codons.

9. NCBI - National Center for Biotechnology Information

10. BLAST - Basic Local Alignment Search Tool

11. Contigs - EST clusters with two or more member ESTs. Groups of clones representing overlapping regions of a genome.

12. PGL - Predicted Gene Location

13. PPS - Predicted Protein Structure

14. AGS - Alternative Gene Structure

15. PGS - Predicted Gene Structure

16. PPGS - Predicted Gene Structure by Protein Spliced Alignment