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 will over the long term select organisms that are better adapted to the current environment. These organisms have to be able to survive long enough to reproduce, and produce viable offspring capable of the same, in order to ensure the continuing survival of their genetic traits.atural selection is a principle that was first proposed by Charles Darwin and Alfred Russel Wallace. The two biologists noted that organisms which were better adapted to their environment tended to survive longer. Better adapted organisms also tend to reproduce more than less well-adapted organisms.