Promoter sequences define the direction of transcription and indicate which DNA strand will be transcribed; this strand is known as the sense strand. Many eukaryotic genes have a conserved promoter sequence called the TATA box, located 25 to 35 base pairs upstream of the transcription start site.romoter sequences are typically located directly upstream or at the 5' end of the transcription initiation site.
Popular Answers. Positive selection: also called (Darwinian selection) variants that increase in frequency until they fix in the relevant population. The selective pressure that leads to this fixation is termed positive selection. Negative selection: Also called purifying selection, it means that selection is purging changes that cause deleterious impacts on the fitness of the host. ...
Natural selection is the differential survival and reproduction of individuals due to differences in phenotype; it is a key mechanism of evolution.actors that affect reproductive success are also important, an issue that Darwin developed in his ideas on sexual selection, which was redefined as being included in natural selection in the 1930s when biologists considered it not to be very important, and fecundity selection, for example.