in proteins, certain specific orderings of secondary structure that may have a functional role and include Î²-Î±-Î² helix-turn-helix, leucine zippers, calcium binding EF hands, zinc fingers and longer orderings that take on a structural domain such as the Î²-barrel and the immunoglobulin fold.
Deoxyribonucleic acid (/diËÉksiËraÉªbÉµ.njuËËkleÉª.É¨k ËaesÉªd/ ; ËÃ¦SÉªD) dna is a molecule that carries most of the genetic instructions used in the, development functioning and reproduction of all known living organisms and many. virusesranscription is carried out by a DNA-dependent RNA polymerase that copies the sequence of a DNA strand into RNA. To begin transcribing a gene, the RNA polymerase binds to a sequence of DNA called a promoter and separates the DNA strands.
DNA is the molecule that encodes the genetic instructions enabling a cell to produce the thousands of proteins it typically needs. The linear sequence of the A, T, C, and G bases in what is called coding DNA determines the particular protein that a short segment of DNA, known as a gene, will encode. But in many organisms, there is much more DNA in a cell than is needed to code for all the necessary proteins. This non-coding DNA was often referred to as junk DNA because it seemed unnecessary. But in retrospect, we did not yet understand the function of these seemingly unnecessary DNA sequences. We now know that non-coding DNA can have important functions other than encoding proteins.