| Term | Description | SeeAlso |
| EcoR1 | A restriction enzyme which cuts DNA when it finds the following palindromic sequence: GAATTC (note that the DNA's complementary strand is CTTAAG, the original sequence spelled backwards, hence a palindrome). After EcorR1 cuts the DNA, each strand is left with an "complementary 5' overhang" of AATTG at their 5' end. EcoR1 is purified from Ecoli bacteria, strain R, and was the first such enzyme that was purified from Ecoli bacteria, hence the name EcoR1. | Restriction Enzyme, DNA Cloning |
| Edward Jenner | Edward Jenner is considered by some to be the father of Immunology. In the late 18th century, having observed that Milk Maids did not contract smallpox, Edward Jenner created a vaccine from the pus of blisters of milkmaids infected with cowpox. He then gave this vaccine to an eight year old boy, who subsequently gained immunity to smallpox. | Virus, Immnology |
| Encapsidate | A virus is said to "encapsidate" its genome (which can be RNA or DNA). In does this by creating a boundary of proteins and/or lipids around the genome. | Virus, Provirus, Reverse Transcriptase |
| Endoplasmic Reticulum | An organelle within the cytoplasm of the cell that is involved in the synthesis, folding and transportation of proteins and other cellular materials. The rough endoplasmic reticulum has ribosomes on its surface. The smooth endoplasmic reticulum is involved in transporting products of the rough endoplasmic reticulum to the Golgi Apparatus and other parts of the cell. | Organelle, Protein, Golgi Apparatus, Ribosome |
| Episome | An automously replicating piece of DNA found in bacteria. These DNA segments are separate from the chromosomes. When a bacterial cell dies, and its DNA spills out, other Bacteria are able to take in the dead bacteria's episomes, and possibly gain selective advantage (e.g. resistence to Penicillin). Episomes are used in DNA cloning to add new DNA segments to bacteria. A Plasmid is a type of episome. | DNA Cloning |
| Epistasis | An interaction between two non-allelic genes which changes the phenotype of one of the genes because it is dependent on the other gene. Often used when one gene suppresses the phenotype of another gene. Also used when one gene's protein is used earlier than another gene's protein in a biochemical pathway. | Allele, Phenotype, Test of Epistasis |
| Epistatic | If you perform a Test of Epistasis on two mutants, A and B, and the double homozygote offspring shows the phenotype of mutant B, then B's phenotype is epistatic to ("Stands upon") A's. It is also likely that the protein produces by A's associated gene is used earlier than B's in the biochemical pathway of interest. | Test of Epistatis, Homozygote, Recessive |
| Epithelial Cells | Cells of the body that cover surfaces. For example, the cells lining the surface of the gut are epithelial cells. | Cell |
| Epitope | A signature sequence of molecules on the surface of an antigen which the immune system recognizes as foreign to the body. For example, antibodies can recognize and bind to certain sequences of amino acids (epitopes wihch are oligopeptides) on a foreign protein. Once the foreign protein has been bound by a number of antibodies, it is disabled and cannot perform its damaging function. | Antibody, Antigen, Protein, Oligopeptide |
| Erythrocyte | A red blood cell (RBC); a cell responsible for transporting oxygen and CO2 between the lungs and tissues of the body. Erythrocytes get their red color from hemoglobin | RBC, Red Blood Cell, Hemoglobin |
| Esterification | A dehydration reaction which links an alcohol molecule to an acid molecule via a covalent bond by removing a water molecule. Esterfication reactions are often used by cells to create new, larger molelcules with desired properties (e.g. to create a more hydrophilic molecule, or for polymerization). | Hydrolysis, Hydrophilic, Polymer, Dehydration Reaction, Condensation Reaction |
| Eukaryote | Organisms with cells that have a nucleus and organelles. Animals, plants, and fungi are eukaryotes. Eukaryotes differ from Prokaryotes and Archaea. Eukaryotes can be single-celled or multicellular organisms. Eukaryotes typically have linear (not circular), double stranded DNA chromosomes. | Prokaryote, Archaea, Organelle |
| Exon | In DNA, the exons are nucleotides that are transcribed into RNA (the introns are skipped). During RNA splicing, the exons are the base pairs which are included in the mature mRNA (the introns are spliced out). A typical human exon is approximately 100-150 base pairs long. | Intron, RNA Splicing, Eukaryote, mature mRNA, immature mRNA |
| Exonuclease Activity | During DNA Replication, DNA Polymerase has an activity called polymerization that adds nucleotides to the end of a new DNA strand. Counterintuitively, it also has an activity that removes bases from the end of the new DNA strand. This activity is called Exonuclease Activity. Because it removes incorrect bases from the end of the strand more often than it removes correctly added bases, this serves as a DNA Proofreading mechanism, avoiding mutations. | DNA Proofreading, Replication, DNA |